Andersen
- The Hippocampus Book |
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Book |
Page |
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Topic |
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Andersen;
Hippocampus Book |
3 |
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The Hippocampal Formation |
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Hippocampus Book |
9 |
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Historical Perspective: Proposed
Functions, Biological Characteristics and Neurobiological Models of
Hippocampus |
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6 |
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37 |
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Hippocampal Neuroanatomy |
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28 |
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38 |
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Hippocampal Formation (diagram) |
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1 |
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38 |
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A common
organizational feature of connections between regions of the neocortex is that
they are largely
reciprocal. |
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38 |
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The entorhinal
cortex can be considered the first step in the intrinsic hippocampal circuit. |
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38 |
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Cells in the superficial
layers of the entorhinal
cortex give rise to axons that project to the dentate gyrus. |
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38 |
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The projections from the entorhinal cortex to the dentate gyrus form part of the major
hippocampal input pathway called the perforant path. |
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38 |
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The dentate
gyrus does not project back to the entorhinal
cortex. |
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38 |
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The pathway between entorhinal cortex and dentate gyrus is unidirectional. |
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38 |
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The
principal cells of the dentate
gyrus, the granule
cells, give rise to axons called mossy fibers that connect with pyramidal cells of the CA3 field of the hippocampus. |
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38 |
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The CA3
cells do not project back to the granule cells of the dentate gyrus. |
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38 |
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Pyramidal cells of CA3
are the source of the major input to the CA1 hippocampal field (the Schaffer collateral axons). |
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39 |
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The CA1 field of the hippocampus projects
unidirectionally to the subiculum. |
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39 |
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From CA1 and subiculum, the pattern of intrinsic connections begins to become somewhat more elaborate. |
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39 |
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CA1 projects not only to the subiculum but also to the entorhinal cortex. |
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Whereas the subiculum does not
project to the presubiculum and a parasubiculum, its more prominent cortical
projection is directed to the entorhinal cortex. |
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39 |
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Both CA1 and the subiculum close
the hippocampal processing loop that begins in the superficial layers of the
entorhinal cortex and ends in its deep layers. |
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39 |
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The hippocampal formation is organized in a fashion that is distinctly different from most other cortical areas. |
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39 |
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Although the volume of the hippocampus is about 10 times larger in monkeys than in rats and 100 times larger in humans than in rats, the basic hippocampal
architecture is common
to all three species. |
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Although the hippocampal formation is often portrayed as a
phylogenetically primitive brain region, it has substantial species differences. |
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39 |
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Prominent role of the rat in current functional analyses of hippocampal formation. |
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39 |
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Far less work has been carried
out on the hippocampus of the mouse, the clear choice for molecular biology
studies. |
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The term hippocampus (derived from the Greek word for seahorse) was first coined during the 16th
century by the anatomist
Arantius (1587). |
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41 |
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Subdivisions of the hippocampus are referred to using
abbreviations of cornu ammonis (CA3, CA2, CA1). |
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A classic article published in 1947 concluded that the hippocampus could not be functioning solely as an olfactory structure. |
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During the 1930s, the neurologist James Papez considered the hippocampus to be a central component of a system for emotional expression. |
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In many
textbooks the hippocampus is still claimed to be the central
component of the so-called Papez circuit. |
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The role of orchestrator of emotional expression is now
closely linked with another prominent medial
temporal lobe structure, the amygdaloid complex. |
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The hippocampus is associated with the term
"limbic system." |
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The origin of the term "limbic system" stems
from the description by neurologist Broca (1878). |
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The number of structures including under the rubric "limbic
system" has escalated
dramatically since the 1950s. |
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42 |
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Several synonymous terms are
still commonly employed for structures of the
hippocampus. |
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The term hippocampus is reserved for the region of the hippocampal
formation that comprises the fields CA3, CA2, CA1. |
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The term hippocampus
formation is applied to a group of distinct
adjoining regions including the dentate
gyrus, hippocampus, subiculum, presubiculum, parasubiculum, and entorhinal cortex. |
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The six
structures of the
hippocampus formation are linked, one to the
next, by a unique and largely unidirectional (functional) neuronal pathways. |
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Early literature on the hippocampus formation (1971) emphasized the first three links of the hippocampal circuitry by applying
the term "trisynaptic circuit" to the ensemble of pathways. |
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(EC -- DG
(synapse 1) -- CA3
(synapse 2) -- CA1
(synapse 3) |
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Projections from CA1 to the subiculum and entorhinal cortex, and a major
projection from the entorhinal
cortex to the neocortex, the tri-synaptic circuit is now
considered to be only a portion of the functional circuitry of the hippocampal formation. |
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The subiculum is the main source of subcortical projections. |
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The entorhinal cortex is a main source of projections to the neocortex. |
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The term hippocampal
formation is widely, though not universally, accepted. |
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Allocortical
-- a term applied to cortical regions having fewer than six layers. |
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Three-layered
cortical regions typically have a single neuronal cell layer with fiber-rich plexiform layers above and below the cell layer. |
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Clarification
of the nomenclature is typically the first sign of maturity for scientific enterprise. |
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The entorhinal
cortex is the only
hippocampal region that unambiguously demonstrates a multilaminate appearance. |
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Given the complex
shape of the hippocampal
formation,
no reference system is wholly adequate, and any description inevitably involves
arbitrary decisions about where to start or finish, which direction is up or down, etc. |
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The dentate
gyrus is considered to be the proximal pole of the hippocampal formation, and the entorhinal cortex is the distal pole. |
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In six-layered
structures, layer I is close to the pial surface, and layer IV is located close to the subcortical
white matter. |
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43 |
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As an electrophysiologist advances an electrode from the dorsal
surface of the brain toward the hippocampus. |
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47 |
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A major fiber pathway associated
with the hippocampal formation is the angular bundle, a fiber bundle
interposed between the entorhinal cortex and the presubiculum and
parasubiculum. |
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4 |
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Hippocampus Book |
47 |
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The perforant
path comprises the afferent entorhinal projections that traverse, or perforate, the subiculum on their way to the dentate gyrus in the hippocampus. |
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The fornix is a continuation of a bundle of hippocampal output fibers to subcortical target structures. |
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48 |
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A third major fiber system associated with the hippocampal
formation is a commissural
system. |
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Commissural
fibers are directed to the contralateral hippocampal
formation. |
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The classic gross anatomical
image of the human hippocampal formation is a prominent bulge in the floor of the temporal horn of the lateral ventricle. |
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The dentate
gyrus is comprised of three
layers. |
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The principal
cell type of the dentate
gyrus is a granule
cell. |
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Each granule
cell is closely
opposed to the other
granule cells,
and in most cases there is no glial sheath
intervening
between the cells. |
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The granule
cell has a characteristic cone shaped tree of spiny dendrites with all the branches directed toward the superficial portion of the molecular layer. |
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Estimates of the number of spines on granule cells ranged from 5600 to 3600. |
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Although cell
proliferation and neurogenesis in the dentate gyrus persist into adulthood, the total
number of granule cells does not vary in adult animals. |
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Hippocampus Book |
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Only infant and juvenile mice
exposed to an "enriched" environments demonstrate a larger dentate
gyrus and a greater number of granule cells that persist into adulthood. |
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Dendritic arborization of the
principal cells in the rat dentate gyrus (diagram) |
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56 |
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The granule cell is the only
principal cell of the dentate gyrus. |
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The most intensively studied interneuron is the pyramidal basket cell. |
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Basket cell axons form plexuses that surround and form synapses with the cell bodies of granule cells. |
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Hippocampal interneurons form a heterogeneous population. |
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Many of the interneuronal
cell types can be distinguished by the distribution of their axonal plexus. |
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Some interneurons have axons that terminate on cell bodies, whereas others have axons that terminate exclusively on the initial
segment of other
axons. |
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Some interneurons have high rates of spontaneous activity and fire in relation to the theta rhythm. |
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Morphological classification of
interneurons of the rat dentate gyrus (diagram) |
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The polymorphic layer harbors a
variety of neuron types, but little is known about many of them. |
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Entorhinal Cortex Projection to the Dentate Gyrus |
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1 |
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Perforant fibers terminate
exclusively in the molecular layer. |
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The dentate gyrus receives
relatively few inputs from subcortical structures. |
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1 |
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61 |
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The major hypothalamic
projections to the dentate gyrus arises from the supramammillary area. |
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1 |
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Hippocampus Book |
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The dentate
gyrus receives a particularly
prominent noradrenergic
input from the pontine
nucleus locus coeruleus. |
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Hippocampus Book |
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The dentate
gyrus receives a minor, diffusely distributed dopaminergic projection that arises mainly from cells located in the
ventral tegmental area. |
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The serotonergic projection that originates from
medial and dorsal divisions of the raphe nuclei also terminates most
heavily in the polymorphic layer. |
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A number of GABAergic
interneurons appear to be preferentially innervated
by the serotonergic fibers. |
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A variety of basket cells are
located just below the granular cell layer and appeared to contribute to an
extremely dense trauma plexus and is confined to the granular cell layer. |
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1 |
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The granules cells give rise to
distinctive unmyelinated axons called mossy fibers. |
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The mossy fibers have unusually
large blue times that form en passant synapses with CA3 pyramidal cells. |
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Although the neuroanatomy of the
hippocampal formation has been analyzed for many years, new component of its
intrinsic circuitry continued to be discovered. |
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The dentate gyrus does not
project any brain region other than the CA3 field of the hippocampus. |
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All dentate
granule cells project to CA3. |
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Mossy fibers give rise to
unique, complex en passant presynaptic terminals called mossy fiber
expansions. |
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Mossy fiber presynaptic
terminals can be as large as 8 µ in diameter but more typically range from 3
to 5 µ. |
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The mossy fiber expansions form
highly irregular, complex, interdigitated attachments with the intricately
branched spines called excrescences that are located on the proximal
dendrites of the CA3 pyramidal cells. |
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The thorny excrescences are so
distinctive that they clearly mark the location of mossy fiber synaptic
termination. |
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Another distinctive feature of
the mossy fiber expansion is the number of active synaptic zones. |
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A single mossy fiber expansion
can make as many as 37 synaptic contacts with a single CA3 pyramidal cell
dendrite. |
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Although a mossy fiber expansion
may be in synaptic contact with more than one complex spine originating from
the same pack dendrite, it does not typically contact spines on two different
dendrites. |
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One mossy fiber expansion does
not typically contact to pyramidal cells. |
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The large mossy fiber expansions
occur approximately every 135 µ along the apparent axon and each mossy fiber
axon forms about 15 of these complex boutons. |
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Each granule cell communicates
with only 15 CA3 pyramidal cells. These 15 pyramidal cells are distributed
throughout the full-length of CA3. |
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Each pyramidal cell is expected
to receive input from about 70 to granule cells. |
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There is substantial evidence
indicating that granule cells
use glutamate as
their primary transmitter. |
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Mossy fibers are
also immunoreactive reactive for several other neuroactive substances. |
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The laminar
organization is generally
similar for all
fields of the hippocampus. |
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The pyramidal
cell layer is tightly packed in CA1 and is more loosely packed in CA2 and CA3. |
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In contrast to the substantial heterogeneity of dendritic organization characteristic of CA3 pyramidal cells, the CA1 pyramidal cells show remarkable homogeneity of their dendritic trees. |
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The total dendritic length of
CA1 pyramidal cells averages approximately 13.5 mm. |
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Some pyramidal cells have one
apical dendrite and others have two. |
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Pyramidal neurons are by far the
most numerous neurons in the hippocampus. |
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As in the dentate
gyrus, there is a fairly heterogeneous group of interneurons in the hippocampus that are scattered through all
layers. |
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Summary of the organization of
hippocampal pyramidal cells produced as computer-generated line drawings of
neurons from CA3, CA2, and CA1. (diagram) |
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Morphological classification of
the interneurons in the hippocampus (diagram) |
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A second type of hippocampal
interneuron is the chandelier, or axo-axonic, cell. |
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Each axo-axonic cell terminates
on approximately 1200 pyramidal cell axon initial segments, and each initial
segment is innervated by 4 to 10 axo-axonic cells. |
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Because most of the excitatory
input to the O-LM cells appear to arise from recurrent collaterals of the
pyramidal cells, this class of interneuron exhibits activity in the distal
dendrites of pyramidal cells in a disynaptic, feedback manner. |
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One of the distinguishing
features of the connectivity of the hippocampus is that most of its synaptic
inputs arise from within its own boundaries. |
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CA3 and CA2
are heavily innervated
by collaterals of their own axons (i.e. associational connections) and
from axons of the contralateral CA3 and CA2. |
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CA1 receives its heaviest input from CA3. |
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There are relatively
few of the extrinsic
inputs to the hippocampus. |
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Entorhinal innervation of CA3 is
mentioned in most studies of the preference at protection. |
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The preferred path perforates
the subiculum and hippocampal fissure en route to the dentate gyrus. |
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Hippocampal Connections within
Neocortex and Amygdaloid Complex |
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The hippocampus sends
projections to and receives projections from numerous other brain regions. |
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Notwithstanding the extremely
important functional relationship between hippocampus and neocortex, it turns
out that only selected parts of a hippocampal formation have discrete,
monosynaptic connections with neocortex. |
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The CA3 and CA2 fields of a
hippocampus have no known connections within neocortex. |
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The hippocampus, like a dentate
gyrus, received noradrenergic and serotonergic inputs from brainstem nuclei. |
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Intrinsic Connections: CA3
Associational Connections and Schaffer Collaterals |
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The major source of input to the
hippocampus is the hippocampus in itself. |
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The CA3 to CA3 associational
connections and the CA3 to CA1 Schaffer collateral connections are
distinguished by their extensive spatial distribution. |
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Through their connections, a
particular pyramidal cell in CA3 can, in theory, interact with other
hippocampal neurons distributed throughout much of the ipsilateral and
contralateral hippocampus. |
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The hippocampal connections,
although widely distributed, are nonetheless systematically organized. |
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All CA3 and CA2 pyramidal cells
give rise highly divergent projections to all portions of the hippocampus. |
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CA3 pyramidal cells gives rise
to highly collateralized axons that distribute fibers both within the
ipsilateral hippocampus (to CA3, CA2, and CA1), to the same fields in the
contralateral hippocampus, and subcortically to the lateral septal nucleus. |
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CA3 does not project to the
subiculum, presubiculum, parasubiculum, or entorhinal cortex. |
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The associational projections
from CA3 to CA3 are organized in a highly systematic fashion. |
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Subiculum is a Major Output
Structure |
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2 |
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This subiculum is a major source
of efferent projections from the hippocampal formation. |
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The subiculum reciprocates the
entorhinal input. |
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Hypothalamus Connections:
Mammillary Nuclei |
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The subiculum provides the major
input to the mammillary nuclei. |
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Presubiculum and Parasubiculum |
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The presubiculum and
parasubiculum receive heavy cholinergic input. |
|
2 |
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The entorhinal cortex is not
only the main entry point for much of the sensory information processed by
the hippocampal formation, it provides the main conduit for processed
information to be relayed back to the neocortex. |
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The entorhinal cortex is the
beginning and end point of an extensive loop of information processing that
takes place in the hippocampal formation. |
|
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The entorhinal cortex is a site
of early, devastating pathology in degenerative diseases such as Alzheimer's
disease. |
|
1 |
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Hippocampus Book |
84 |
|
Standard six-layered
laminar organization
applied to the isocortex. |
|
0 |
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Hippocampus Book |
84 |
|
There are four cellular layers
(II, III, V, VI) and two acellular or plexiform layers (I, IV). |
|
0 |
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Hippocampus Book |
84 |
|
Layer 1 -- the most superficial
plexiform or molecular layer, which is so poor but rich in transversely
oriented fibers. |
|
0 |
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Hippocampus Book |
84 |
|
Layer 2 -- containing mainly
medium-sized to large stellate cells in a population of small pyramidal cells
that team tend to be grouped in clusters particularly in the lateral
entorhinal area. |
|
0 |
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84 |
|
Layer 3 -- containing cells of
various sizes and shapes but predominately pyramidal cells. |
|
0 |
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84 |
|
Layer 4 -- a cell-free layer
located between layers 3 and 5 that is most apparent in portions of the
entorhinal cortex. |
|
0 |
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Hippocampus Book |
84 |
|
Layer 5 -- a cellular layer,
which can be subdivided into bands. |
|
0 |
Andersen;
Hippocampus Book |
84 |
|
Layer 6 -- containing a highly
heterogeneous population of cells sizes and shapes. They cell density
decreases toward the border with the white matter. |
|
0 |
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Hippocampus Book |
91 |
|
The dentate gyrus and the CA3
field of the hippocampus do not project back to the entorhinal cortex. |
|
7 |
Andersen;
Hippocampus Book |
93 |
|
The major portion of the
entorhinal cortex does not contribute projections to the human modal areas of
the neocortex. |
|
2 |
Andersen;
Hippocampus Book |
93 |
|
The bulk of neocortically
directed projections from the entorhinal cortex are to higher-order
associational and polysensory cortices and not to sensory or motor regions. |
|
0 |
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Hippocampus Book |
93 |
|
Among the cortical areas that do
receive entorhinal inputs are the infralimbic, prelimbic, orbitofrontal,
agranular insular, perrirhinal, and postrhinal cortices. |
|
0 |
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Hippocampus Book |
93 |
|
The entorhinal
cortex receives a number of subcortical inputs. |
|
0 |
Andersen;
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93 |
|
Whereas some inputs to the
entorhinal cortex, such is the monoaminergic and cholinergic inputs, may be
viewed as largely modulatory, others such as the input from the amygdala
complex, might also provide additional sources of information. |
|
0 |
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Hippocampus Book |
93 |
|
The substantial
input to the entorhinal
cortex from the amygdaloid
complex is presumably conveying information about
the emotional state
of the organism. |
|
0 |
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Hippocampus Book |
93 |
|
The entorhinal
cortex sends feedback
projections to the amygdala. |
|
0 |
Andersen;
Hippocampus Book |
93 |
|
The entorhinal
cortex
projects bilaterally to the striatum, particularly to the nucleus accumbens and adjacent parts of the olfactory tubercle. |
|
0 |
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Hippocampus Book |
93 |
|
The entorhinal
cortex
receives cholinergic innervation mainly from the septum. |
|
0 |
Andersen;
Hippocampus Book |
93 |
|
The entorhinal cortex projects
back to the septal region. |
|
0 |
Andersen;
Hippocampus Book |
93 |
|
The entorhinal
cortex
receives defuse inputs from various structures in the hypothalamus. |
|
0 |
Andersen;
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94 |
|
Summary of the reciprocal connections between the
amygdala and the hippocampal formation and the perrirhinal and parahippocampal cortices.
(diagram) |
|
1 |
Andersen;
Hippocampus Book |
94 |
|
There is no evidence that the
entorhinal cortex projects back to the thalamus. |
|
0 |
Andersen;
Hippocampus Book |
94 |
|
Brain Stem Inputs to the
Entorhinal Cortex |
|
0 |
Andersen;
Hippocampus Book |
94 |
|
The entorhinal
cortex received dopaminergic
input from cells located in the ventral tegmental area. |
|
0 |
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Hippocampus Book |
94 |
|
Serotonergic innervation arises from the central and dorsal raphe nuclei and terminates
diffusely
in all layers
of the entorhinal cortex. |
|
0 |
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94 |
|
The noradrenergic
locus coeruleus supplies the entorhinal cortex with diffusely
organized noradrenergic input. |
|
0 |
Andersen;
Hippocampus Book |
95 |
|
A variety
of peptides and other chemical markers have been shown to subdivide their populations in GABAergic interneurons. |
|
1 |
Andersen;
Hippocampus Book |
95 |
|
Another class of substances that
appear to mark certain subsets
of GABAergic neurons
selectively is the family of calcium-binding proteins. |
|
0 |
Andersen;
Hippocampus Book |
95 |
|
Although the precise
function of the various calcium-binding proteins has not
been well established, their existence has provided a useful anatomical tool. |
|
0 |
Andersen;
Hippocampus Book |
95 |
|
When researchers view the stained sections of hippocampus from rat, monkey, and human, it is immediately apparent they are looking at the same brain region. |
|
0 |
Andersen;
Hippocampus Book |
95 |
|
The entorhinal
cortex has many more subdivisions in the monkey and human than in rats; and the laminar
organization is much
more distinct in the primate
brain. |
|
0 |
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Hippocampus Book |
96 |
|
Although we can address certain
issues concerning cell number
and distribution in
the human brain, we are unable to say anything about patterns of connectivity in the human hippocampal formation. |
|
1 |
Andersen;
Hippocampus Book |
96 |
|
In CA1, there are only three times more pyramidal cells in the monkey than in the rat, whereas there are 35 times more cells in humans than in rats. |
|
0 |
Andersen;
Hippocampus Book |
104 |
|
Our understanding of the human hippocampus is necessarily primitive compared to that of the rat or the monkey. |
|
8 |
Andersen;
Hippocampus Book |
104 |
|
Molecular biology may someday
provide new pathway selective markers that allow comparative studies of the
rat, monkey, and human hippocampal formation. |
|
0 |
Andersen;
Hippocampus Book |
104 |
|
The CA1
field of the hippocampus is thicker in humans than in monkeys; in some regions it is as much as 30 cells thick. |
|
0 |
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104 |
|
In addition to being thicker,
the CA1 pyramidal cell layer
takes on a distinctive multi-laminate appearance, with cells of different size and shape
predominating at different depths of the layer. |
|
0 |
Andersen;
Hippocampus Book |
106 |
|
Little is known about the morphology of cells in the human dentate
gyrus. |
|
2 |
Andersen;
Hippocampus Book |
106 |
|
The human entorhinal cortex has attracted
considerable attention because of its vulnerability in Alzheimer's disease. |
|
0 |
Andersen;
Hippocampus Book |
106 |
|
There is little information
concerning the organization of connections in the human
hippocampal formation owing to the fact that most neuroanatomical tracing
techniques require injection of tracers into the living brain. |
|
0 |
Andersen;
Hippocampus Book |
106 |
|
Magnetic Resonance Imaging of
the Human Hippocampal Formation |
|
0 |
Andersen;
Hippocampus Book |
106 |
|
Grid of 4 mm squares over the medial temporal lobe, which is typical for fMRI. Might expect to have one voxel over the subiculum or perhaps
two voxels over the entorhinal cortex. Other voxels would overlap adjacent
fields, such as the dentate gyrus and CA3. (diagram) |
|
0 |
Andersen;
Hippocampus Book |
106 |
|
With the current functional imaging technologies,
it is difficult to define specific activations for
defined subfields of the hippocampal formation. |
|
0 |
Andersen;
Hippocampus Book |
107 |
|
Much of a neuroanatomical
information available has been gained from studies of the rat. |
|
1 |
Andersen;
Hippocampus Book |
107 |
|
A variety of models for temporal lobe epilepsy have been advance based on cell
degeneration and fiber
sprouting in the rat
hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
107 |
|
It would not
be surprising if substantial
differences exist in the cellular morphology, connectivity, and chemical neuroanatomy of the hippocampal formation across species. |
|
0 |
Andersen;
Hippocampus Book |
108 |
|
Summary of the transverse
organization of the connections through the hippocampal formation (diagram) |
|
1 |
Andersen;
Hippocampus Book |
109 |
|
Serial and Parallel Processing
in the Hippocampal Formation |
|
1 |
Andersen;
Hippocampus Book |
109 |
|
A unique feature of the
intrinsic hippocampal circuitry is the largely unidirectional organization of the
projections that interconnect the various hippocampal regions. |
|
0 |
Andersen;
Hippocampus Book |
109 |
|
The intrinsic
hippocampal circuitry
has both serial and parallel projections. |
|
0 |
Andersen;
Hippocampus Book |
109 |
|
The entorhinal cortex contributes many
parallel projections
to several fields of
the hippocampal formation. |
|
0 |
Andersen;
Hippocampus Book |
109 |
|
The existence of prominent associational
connections in the dentate
gyrus, hippocampus, and
entorhinal cortex also provides a substrate for polysynaptic activation in hippocampal circuits. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
Morphological Development of the
Hippocampus |
|
6 |
Andersen;
Hippocampus Book |
115 |
|
The enormous number of specific
interneuronal connections that serve the complex functions of immature CNS
are formed during development. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
Modern genetic approaches
include mutant mice lacking or overexpressing genes important for
developmental processes. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
Phylogenetic development of the
hippocampal formation has demonstrated that it is a form of phylogenetically
old cortex, the archicortex, that develops in the medial wall of the
telencephalic vesicle. |
|
0 |
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Hippocampus Book |
115 |
|
Owing to the expansion of the
cerebral cortex in higher vertebrates, the hippocampal
formation is
translocated medially and ventrally into the inferior portion of the lateral ventricle. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
As in other organs, it is
important to understand the signals governing cell proliferation. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
Postmitotic
neurons migrate to their final destination. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
Upon arrival in their appropriate structure or layer, the postmigratory neuroblasts start to
develop their processes. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
Why do the nonprincipal cells
that invade the hippocampus from the ganglionic eminence form such a
heterogeneous population of neurons? |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
To what extent is neuronal activity involved in the differentiation of dendrites, dendritic spines, and synaptic contacts? |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
The development of major
hippocampal connections -- determinants of pathfinding, target layer
recognition, and synaptic formation of hippocampal afferents. |
|
0 |
Andersen;
Hippocampus Book |
115 |
|
Most of our knowledge about cell formation in the rodent hippocampal formation dates back
to seminal studies in
1965. |
|
0 |
Andersen;
Hippocampus Book |
116 |
|
Research has provided
descriptions of the origin, the time course of generation, and the laminar
distribution of principal neurons, pyramidal neurons, and granule cells. |
|
1 |
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Hippocampus Book |
116 |
|
Stem cells of both pyramidal neurons and granule
cells originate from the ventricular germinal layers that
are located below the ventricular
wall along the CA1
area. |
|
0 |
Andersen;
Hippocampus Book |
116 |
|
The multiplying
neurons directly migrate from the ventricular zone to their final target region. |
|
0 |
Andersen;
Hippocampus Book |
116 |
|
Except for the CA3 pyramidal cells, the route of migration is short because the hippocampus closely follows the curve of the ventricle. |
|
0 |
Andersen;
Hippocampus Book |
116 |
|
The pyramidal
cell layer of the hippocampus forms quite
early in
the human brain. |
|
0 |
Andersen;
Hippocampus Book |
116 |
|
In the human
brain, the pyramidal
cell layer of the hippocampus is formed during the first half of pregnancy. |
|
0 |
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Hippocampus Book |
116 |
|
in the human
brain, the CA1 to CA3
regions of the hippocampus can be differentiated as early as during the 16th
embryonic week. |
|
0 |
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Hippocampus Book |
116 |
|
Regional differentiation of the hippocampal formation substantially
precedes that of the neocortex. |
|
0 |
Andersen;
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116 |
|
The formation of the granule cell layer of the dentate gyrus differs in many respects from that of the pyramidal cell layer of the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
116 |
|
The generation of granule cells lasts a much longer time than that of pyramidal
neurons. |
|
0 |
Andersen;
Hippocampus Book |
116 |
|
There is substantial evidence
that the generation of granule cells continues long into the postnatal period and, at a reduced
level, into adulthood. |
|
0 |
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116 |
|
In rats, the time span though of
cell generation is approximately 3 times longer than that of pyramidal
neurons and is likely to continue for the rest of the animal's life. |
|
0 |
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116 |
|
In humans, granule cell
formation
lasts more than 30 weeks, beginning at approximately the 13th
embryonic week. |
|
0 |
Andersen;
Hippocampus Book |
117 |
|
There is evidence for adult neurogenesis in the human dentate gyrus. |
|
1 |
Andersen;
Hippocampus Book |
117 |
|
The route
of migration of the postmitotic granule cells is much
longer than that of
pyramidal neurons. |
|
0 |
Andersen;
Hippocampus Book |
117 |
|
Postmitotic
granule cells must migrate from the ventricular germinal layer along the already
formed hippocampus where they form
the cup-shaped dentate gyrus that surrounds the tip of CA3. |
|
0 |
Andersen;
Hippocampus Book |
117 |
|
The enduring cell proliferation in the hilar
region
mainly represents local generation of granule
cells. |
|
0 |
Andersen;
Hippocampus Book |
117 |
|
Proliferating cells persists in
the hilar region during the entire period of granule cell neurogenesis, and
persisting hilar stem cells may also form new neurons during adulthood. |
|
0 |
Andersen;
Hippocampus Book |
117 |
|
There is little
morphological variability among granule cells even though they may
be located in different places in the granule cell layer and may be born at
different time points. |
|
0 |
Andersen;
Hippocampus Book |
117 |
|
The morphological
uniformity
of granule cells leads to the assumption that all granule cells originate from the same stem cell population. |
|
0 |
Andersen;
Hippocampus Book |
117 |
|
Most of the granule cells display similar
features in the rodent and primate dentate gyrus. |
|
0 |
Andersen;
Hippocampus Book |
118 |
|
Epileptic
seizures appear to lead to an increased number of granule cells with basal
dendrites in the human
dentate gyrus. |
|
1 |
Andersen;
Hippocampus Book |
118 |
|
Dentate granule cells in
different mammalian species form a largely homogeneous neuronal population. |
|
0 |
Andersen;
Hippocampus Book |
118 |
|
Dendritic morphology of dentate
granule cells in different mammalian species may be modified to some extent
depending on the local environment or pathological factors. |
|
0 |
Andersen;
Hippocampus Book |
118 |
|
Local
circuit neurons of
the hippocampal formation differ from the principal cells in both their morphological and developmental features. |
|
0 |
Andersen;
Hippocampus Book |
118 |
|
In contrast to the morphologically uniform granule cells and pyramidal neurons, local circuit neurons of the hippocampal formation form a heterogeneous
population. |
|
0 |
Andersen;
Hippocampus Book |
118 |
|
Even the classic basket cell can be subdivided into five types based on differences in
location and dendritic arborization. |
|
0 |
Andersen;
Hippocampus Book |
118 |
|
In addition to dendritic morphology, differences in axonal projections also distinguish
subpopulations of local
circuit neurons
in
both the dentate gyrus and the hippocampus
proper. |
|
0 |
Andersen;
Hippocampus Book |
120 |
|
In the neocortex, cell layers are formed in an inside-out manner; i.e. early-generated neurons form deeper layers, whereas
superficial layers are established by cells late in ontogenetic development. |
|
2 |
Andersen;
Hippocampus Book |
120 |
|
As in the neocortex, the hippocampus follows a similar inside-out
migration. |
|
0 |
Andersen;
Hippocampus Book |
120 |
|
Migration processes are under fairly strict genetic control. |
|
0 |
Andersen;
Hippocampus Book |
120 |
|
When describing the development of neuronal connections, it is useful
to distinguish at least three processes: (1) axonal
pathfinding, (2) target
recognition,
(3) synapse formation. |
|
0 |
Andersen;
Hippocampus Book |
120 |
|
There is substantial and
increasing evidence that a variety of molecules are involved in the
development of neuronal connection. |
|
0 |
Andersen;
Hippocampus Book |
121 |
|
The various semaphorins and their receptors; the plexins, and the ephrin family of tyrosine kinases and their ligands, contribute to establishing hippocampal circuitry. |
|
1 |
Andersen;
Hippocampus Book |
121 |
|
Entorhinal Connections |
|
0 |
Andersen;
Hippocampus Book |
121 |
|
Neuroanatomists have been
intrigued by the unique course
of the entorhino-hippocampal projection, which perforates the subiculum and hippocampal fissure en route to the dentate gyrus. |
|
0 |
Andersen;
Hippocampus Book |
122 |
|
The growth of the neuronal
fibers along CR cell axons is likely to be controlled by a variety of
repulsive and attractive molecules. |
|
1 |
Andersen;
Hippocampus Book |
122 |
|
How do entorhinal fibers
recognize their target layer? Current evidence strongly suggests that
components of the extracellular matrix play an important part in the
segregation of hippocampal afferents. |
|
0 |
Andersen;
Hippocampus Book |
123 |
|
Secreted molecules such as the
semaphorins, membrane-bound receptors, extracellular matrix components, and a
template formed by CR cell axons are likely to be involved in the directed
growth and layer-specific termination of entorhinal fibers. |
|
1 |
Andersen;
Hippocampus Book |
123 |
|
Target cells are unlikely to be
involved in pathfinding of entorhinal axons and target layer recognition. |
|
0 |
Andersen;
Hippocampus Book |
123 |
|
Many questions concerning the
layout-specific termination of entorhinal fibers remain open at present. |
|
0 |
Andersen;
Hippocampus Book |
123 |
|
Commissural
fibers, originating from CA3 pyramidal neurons and hilar mossy cells, project via the
hippocampal commissure
to the contralateral hippocampus and intake gyrus. |
|
0 |
Andersen;
Hippocampus Book |
124 |
|
Since the commissural fibers
arrive relatively late in the hippocampus and dentate gyrus, the pioneered
neurons may not be required, because the target cells, the principal neurons,
are already present at that time and have already grown a dendritic arbor. |
|
1 |
Andersen;
Hippocampus Book |
124 |
|
Whereas the entorhinal fibers
require pioneer neurons, the commissural afferents establish contacts
directly with principal cell dendrites. |
|
0 |
Andersen;
Hippocampus Book |
124 |
|
Little is known about the molecules involved in pathfinding and target recognition of commissural fibers. |
|
0 |
Andersen;
Hippocampus Book |
125 |
|
The septohippocampal projection
consists of two parts: a cholinergic one and a GABAergic one. |
|
1 |
Andersen;
Hippocampus Book |
125 |
|
The cells of origin for both
parts of the septohippocampal projection are located in the medial septal
nucleus/diagonal band complex (MSDP). |
|
0 |
Andersen;
Hippocampus Book |
125 |
|
The hippocampus-septal
projection develops relatively early and terminates in the medial septum. |
|
0 |
Andersen;
Hippocampus Book |
125 |
|
The early termination of the
hippocampo-septal projection in the medial septal nucleus has led to the
hypothesis that the early formed hippocampo-septal projection serves as a
template by which septohippocampal fibers find their way to the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
125 |
|
It has been shown that growth
cones of septohippocampal fibers grow along hippocampo-septal axons. |
|
0 |
Andersen;
Hippocampus Book |
125 |
|
Septohippocampal cholinergic
fibers are found in all layers of the hippocampal formation, but are
certainly more concentrated in cell body layers. |
|
0 |
Andersen;
Hippocampus Book |
125 |
|
Septohippocampal GABAergic
projection cells display a high target cells specificity, terminating almost
exclusively on GABAergic interneurons in the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
126 |
|
The septal cholinergic fibers
establish contacts with both principal neurons and interneurons, and they are
contacts are on cell bodies, dendritic shafts, and spines. |
|
1 |
Andersen;
Hippocampus Book |
126 |
|
Nerve growth factor (NGF) is
synthesized by GABAergic hippocampus neurons, which are distributed over all
hippocampal layers. |
|
0 |
Andersen;
Hippocampus Book |
126 |
|
Different cellular and molecular
factors, probably being effected only during certain development time
windows, are involved in the formation of the different projections to the
hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
126 |
|
When describing the formation of
a pathway, it is useful to distinguish between axonal pathfinding, target
recognition, and synapse formation. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
For pathfinding and target recognition, pioneer neurons provide a template by an early-formed projection. |
|
1 |
Andersen;
Hippocampus Book |
127 |
|
Membrane-bound and soluble
molecules and components of the extracellular matrix seem to play a role at
different times of development. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
A variety of ligand-receptor
interactions, by their repulsive or attractive effects, may guide the growth
cone of a growing axon in the target region. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Extracellular matrix molecules
may be essential for segregation of fiber systems in the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Studies of synapse formation is
a rapidly-developing field. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Mechanisms leading to new
contacts or changes in the shape of synapses or spines may not only be
effective during development but may also underlie plastic processes in the
adult organism. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Researchers have observed new spines formed during the
development of long term potentiation (LTP). |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Researchers have shown that
estrogen application induces new spines on CA1 pyramidal cell dendrites, an
effect likely caused by estrogen acting primarily on CA3 pyramidal cells and
inducing the sprouting of Schaffer collaterals to CA1 pyramidal neurons. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Research studies have shown that
estrogens synthesized in the hippocampus are important for hippocampal synaptic plasticity. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Future studies will help
establish whether estrogen-induced
plastic changes in spine synapses are specific for hippocampal neurons or are a more general phenomenon
occurring at many synapses in the central nervous system. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Differentiation of pyramidal
neurons and granule cells continues for a relatively long period in rodents
and primates. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
Spine density increases until the time of sexual maturation. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
In humans, spine density and total dendritic length of CA1 pyramidal neurons
increase until at least the third postnatal year. |
|
0 |
Andersen;
Hippocampus Book |
127 |
|
In contrast to the long-term
differentiation of principal cells, local circuit neurons in the primate
hippocampal formation but to a fast. |
|
0 |
Andersen;
Hippocampus Book |
128 |
|
Arrival of afferents at the rat
hippocampus formation continues with the development of their target cells. |
|
1 |
Andersen;
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128 |
|
In both rodents and humans the late development of the intrahippocampal
associational connections may influence the maturation of the entire hippocampal network. |
|
0 |
Andersen;
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133 |
|
Structural and Functional
Properties of Hippocampal Neurons |
|
5 |
Andersen;
Hippocampus Book |
133 |
|
Understanding the function of the hippocampus includes the unique morphological and physiological properties of the great variety of neurons. |
|
0 |
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133 |
|
Although long
term potentiation was
first described in the dentate
gyrus, most of the studies in the decades that followed in its
original description have focused on the CA1
region. |
|
0 |
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134 |
|
Studies are CA1 are more
numerous in adjacent CA3 because it is generally easier to keep cells in this
region are alive and healthy in slice preparations. |
|
1 |
Andersen;
Hippocampus Book |
134 |
|
CA1 pyramidal neurons have been the focus of several
studies of dendritic integration because of the large primary
apical dendrite, from which dendritic patch-clamp recordings
can be obtained routinely. |
|
0 |
Andersen;
Hippocampus Book |
134 |
|
Hippocampus studies have contributed to tremendous advances in understanding
synaptic transmission, integration, and
plasticity in the CNS. |
|
0 |
Andersen;
Hippocampus Book |
134 |
|
To elaborate label branching
dendritic trees emerged from the pyramid-shaped soma of CA1 neurons. |
|
0 |
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|
Basal dendrites occupy the stratum oriens, and the apical dendrites occupy the stratum radium and stratum lacunosum-moleculare. |
|
0 |
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134 |
|
The combined
length of all CA1 dendritic branches is 12.0 to 13.5 mm. |
|
0 |
Andersen;
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134 |
|
CA1 dendrites studied with
spines. |
|
0 |
Andersen;
Hippocampus Book |
134 |
|
Along the length of the primary apical dendrite, several dendritic branches emerge obliquely in the stratum radiatum. |
|
0 |
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134 |
|
Oblique dendrites branch no more than a few times, and with a typical branch bifurcating just once at a location close to its origin from the apical trunk. |
|
0 |
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|
After the primary
apical trunk enters the stratum lacunosum-moleculare
the
apical dendrites continue to branch, forming a structure called the apical tuft. |
|
0 |
Andersen;
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134 |
|
Emerging from the base of the pyramidal soma are two to eight dendrites, forming a basal dendritic tree with about 40 terminal segments. |
|
0 |
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|
Many other organelles found in the cell body extend into the proximal
apical dendrites of CA1
neurons.
These include structures such as the smooth
endoplasmic reticulum (SER) and the Golgi apparatus. |
|
0 |
Andersen;
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134 |
|
Microtubules, neurofilaments,
and actin are prominent and serve transport and motility functions, and are
likely to be important in synaptic plasticity. |
|
0 |
Andersen;
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134 |
|
A network of smooth endoplasmic
reticulum is also present in dendrites, where it is likely to serve important
functions in calcium buffering and release. |
|
0 |
Andersen;
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134 |
|
The smooth endoplasmic reticulum
forms a continuous reticulum, which can extend into dendritic spines. |
|
0 |
Andersen;
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134 |
|
Mitochondria
are also numerous in dendrites and are often associated with the smooth
endoplasmic reticulum. |
|
0 |
Andersen;
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134 |
|
Dendritic mitochondria likely contribute to calcium
handling in addition to serving as the primary energy source. |
|
0 |
Andersen;
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135 |
|
CA1 dendritic morphology,
spines, and synaptic inputs and outputs. (diagram) |
|
1 |
Andersen;
Hippocampus Book |
136 |
|
Ribosomes
are present in CA1 dendrites, where they are usually clustered in the form of polyribosomes. |
|
1 |
Andersen;
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136 |
|
CA1 pyramidal neurons are covered with about 30,000
dendritic spines. |
|
0 |
Andersen;
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136 |
|
The dendritic spines studding the surface of CA1 dendrites exhibit a broad range of size and morphological complexity. |
|
0 |
Andersen;
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136 |
|
Thin spines are long, narrow
protrusions terminating in a small, bulbous head. |
|
0 |
Andersen;
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136 |
|
Sessile spines are long, narrow
protrusions that do not terminate in a head. |
|
0 |
Andersen;
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136 |
|
Mushroom spines have a narrow
neck and a large, bulbous head. |
|
0 |
Andersen;
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136 |
|
Branched spines consists of a neck that branches and terminates in two
bulbous heads, each of which receives synaptic input from different axons. |
|
0 |
Andersen;
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136 |
|
Spine structure is not
static but may change in response to neurotransmitter
activation or environmental and hormonal signals. |
|
0 |
Andersen;
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136 |
|
Growth of new
spines
and changes in
the structure of existing spines are possible
substrates of synaptic plasticity in the hippocampus. |
|
0 |
Andersen;
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137 |
|
Spines also
contained numerous organelles, including smooth endoplasmic
reticulum (SER). |
|
1 |
Andersen;
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137 |
|
The presence of a large number
of molecules and organelles in spines, together with the separation that the spine neck provides from the dendritic shaft and other spines, has led to the hypothesis that spines function as isolated molecular compartments. |
|
0 |
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137 |
|
A prominent
feature of almost all spines throughout the nervous system is a postsynaptic
density (PSD),
an electron-dense thickening of the postsynaptic membrane. |
|
0 |
Andersen;
Hippocampus Book |
137 |
|
The PSD is located adjacent to the presynaptic bouton associated with the spine. |
|
0 |
Andersen;
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137 |
|
Functionally, the PSD is a biochemical specialization that allows numerous molecules (e.g. receptors, kinases, cytoskeletal elements) to be associated in a structured array at the synapse. |
|
0 |
Andersen;
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137 |
|
NMDA receptors, which mediate a slow synaptic
current blocked in a voltage-dependent manner, occupy a disk-like space near the center of the PSD. |
|
0 |
Andersen;
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137 |
|
AMPA receptors, which mediate a fast synaptic
current, are distributed
more evenly
throughout the PSD. |
|
0 |
Andersen;
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137 |
|
Individual excitatory synapses on CA1
neurons
vary considerably in their expression of AMPA and
NMDA receptors. |
|
0 |
Andersen;
Hippocampus Book |
137 |
|
Whereas the
number of NMDA receptors is relatively invariant, a tremendous range exists in the number of AMPA receptors at individual synapses. |
|
0 |
Andersen;
Hippocampus Book |
137 |
|
CA1 neurons receive input from
both excitatory and inhibitory presynaptic neurons. |
|
0 |
Andersen;
Hippocampus Book |
137 |
|
The
principal excitatory inputs to CA1 neurons arrive from the entorhinal cortex and CA3
pyramidal neurons. |
|
0 |
Andersen;
Hippocampus Book |
137 |
|
Inputs from
pyramidal neurons in
the entorhinal cortex project to CA1 neurons via the perforant path (PP). |
|
0 |
Andersen;
Hippocampus Book |
137 |
|
Inputs from
CA3 pyramidal neurons on both sides of the brain form the Schaffer collateral/commissural system (SC). |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
Numerous inhibitory
neurons also target CA1 pyramidal neurons. Some of these interneurons target the soma and axon, and others target dendrites. |
|
1 |
Andersen;
Hippocampus Book |
138 |
|
CA1
pyramidal neurons also receive neuromodulatory inputs from a number of subcortical
nuclei. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
A large input arriving from the septum contains cholinergic afferents. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
Projections
from the locus coeruleus contain noradrenergic inputs. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
Raphe nuclei
projection contains serotonergic inputs. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
The ventral
tegmental area sends dopaminergic afferents to the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
CA1
pyramidal neurons express numerous receptor subtypes for each of
the neuromodulators. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
A single axon emanates from the
pyramidal soma of CA1 pyramidal neurons and projects through the stratum
oriens. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
CA1 axons branch extensively, forming collaterals with several targets, both within and beyond the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
Unlike CA3 pyramidal neurons,
CA1 cells do not make many connections among themselves. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
CA1-interneuron connectivity is
much higher than CA3, and the strength of excitatory postsynaptic potentials
(EPSPs) on interneurons is powerful. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
The most significant
intrahippocampal projection of CA1 neurons is to pyramidal neurons in the
subiculum. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
The subiculum forms a powerful output of the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
138 |
|
CA1 axons collateralized
extensively in the subiculum but form a topological projection. |
|
0 |
Andersen;
Hippocampus Book |
139 |
|
The CA1 axon, which has a
diameter of less than 1 µ, has numerous en passant and terminal synaptic
specializations along its length. |
|
1 |
Andersen;
Hippocampus Book |
141 |
|
CA1
pyramidal neurons, like most neurons in the
brain, have long and extensively branching dendrites. |
|
2 |
Andersen;
Hippocampus Book |
144 |
|
Detailed compartmental modeling
of CA1 neurons suggests that functional coupling between the soma and distal
dendrites is limited. |
|
3 |
Andersen;
Hippocampus Book |
144 |
|
Attenuation of synaptic
potentials and CA1 dendrites. |
|
0 |
Andersen;
Hippocampus Book |
144 |
|
Mechanisms of compensation for
synaptic attenuation and CA1 dendrites. |
|
0 |
Andersen;
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145 |
|
Passive Versus Active Dendrites |
|
1 |
Andersen;
Hippocampus Book |
146 |
|
Action potentials from CA1
neurons coupled by gap junctions have been implicated. |
|
1 |
Andersen;
Hippocampus Book |
146 |
|
Dendrites of CA1 pyramidal
neurons are capable of generating active responses owing to the presence of
voltage-gated channels. |
|
0 |
Andersen;
Hippocampus Book |
146 |
|
Studies have led to the
hypothesis that action potentials might be initiated in dendrites. |
|
0 |
Andersen;
Hippocampus Book |
146 |
|
The site of action potential of
initiation has been narrowed to a region near their first node of Ranvier in
the axon. |
|
0 |
Andersen;
Hippocampus Book |
146 |
|
Following their initiation in
the axon, action potentials and they did dendritic tree of CA1 neurons. |
|
0 |
Andersen;
Hippocampus Book |
146 |
|
Add 300 µ, the back-projecting
action potential amplitude is about half of the somatic amplitude. |
|
0 |
Andersen;
Hippocampus Book |
146 |
|
Even for modest
firing frequencies such as 20 Hz, the action potential amplitude,
measured about 300 µ from the soma, attenuates to less than half of its amplitude at
lower frequencies. |
|
0 |
Andersen;
Hippocampus Book |
152 |
|
Functional implication of
voltage-gated channels in CA1 dendrites: Synaptic Integration and Plasticity |
|
6 |
Andersen;
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152 |
|
Dendrites
are able to generate
a variety of active
responses,
including back-propagating action potentials and dendritic
Na+ and Ca2+ spikes. |
|
0 |
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152 |
|
The CA1
pyramidal neuron is
arguably the most extensively studied neuron with respect to resting membrane
properties, dendritic function, and synaptic integration. |
|
0 |
Andersen;
Hippocampus Book |
152 |
|
Voltage attenuation in dendrites is predicted to be enormous for the near-passive condition. |
|
0 |
Andersen;
Hippocampus Book |
152 |
|
The neuron appears to compensate for voltage attenuation in dendrites by at least two
key mechanisms: (1) synapse conductance
scaling, and (2) excitable dendrites containing myriad voltage-gated channels. |
|
0 |
Andersen;
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153 |
|
One emergent property of the complexity of the CA1 dendritic tree appears to be coincidence detection for perforant-path and Schaffer-collateral synaptic
inputs. |
|
1 |
Andersen;
Hippocampus Book |
153 |
|
CA3 Pyramidal Neurons |
|
0 |
Andersen;
Hippocampus Book |
153 |
|
CA3
pyramidal neurons have been studied extensively, because of the unique
functional specializations formed by the mossy fiber inputs from the dentate gyrus and because of the extensive axon collaterals between CA3 neurons, which create a highly
interconnected and excitable network. |
|
0 |
Andersen;
Hippocampus Book |
155 |
|
CA3
pyramidal neurons receive three
prominent forms of excitatory synaptic input -- (1) mossy
fiber input from dentate granule cells, (2) input from entorhinal cortex via the perforant path, (3) from axons of other CA3 neurons. |
|
2 |
Andersen;
Hippocampus Book |
155 |
|
The commissural/associational
inputs to CA3 are numerous and originate from CA3 neurons on both sides of
the brain. |
|
0 |
Andersen;
Hippocampus Book |
155 |
|
The extensive
network of recurrent
collaterals has led to the
postulate that the CA3 region may function
as an autoassociative network involved in memory storage and recall. (Rolls) |
|
0 |
Andersen;
Hippocampus Book |
155 |
|
A side
effect of the extensive
interconnectivity is that the CA3
network is highly excitable and prone to the seizure activity when inhibition is suppressed. |
|
0 |
Andersen;
Hippocampus Book |
155 |
|
CA3 neurons also receive cholinergic input from the medial septal nucleus. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
A comparison of the properties
of mossy fiber synaptic transmission to AMPA receptor properties in CA3
dendrites suggest that a typical quantal event would consist of 35 AMPA
receptors being activated by a single quantum of glutamate. |
|
1 |
Andersen;
Hippocampus Book |
156 |
|
The high
density of AMPA
receptors and the large number of synaptic specializations on each thorny excrescence
accounts for the large
size and variability of unitary mossy fiber synaptic currents. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
CA3
pyramidal neurons also receive substantial
innervation
from inhibitory interneurons. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
In addition to the somatic and axonal inhibition, which presumably limits action potential initiation, a number of interneurons target CA3 dendrites. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
The dendritic
inhibition
limits the initiation and enhances termination of dendritic
calcium spikes. |
|
0 |
Andersen;
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156 |
|
Each CA3
pyramidal neuron gives rise to a single axon, which projects
bilaterally to CA3, CA2,
and CA1 regions, as well as to the lateral septal nucleus. |
|
0 |
Andersen;
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156 |
|
Individual axons are thin and
myelinated with abundant en passant boutons or varicosities. |
|
0 |
Andersen;
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156 |
|
CA3 axons project primarily to the CA1
region
but also collateralize
extensively
within CA3. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
The total
length of the CA3 collaterals in the ipsilateral hippocampus has been estimated at 150 to 300
mm. |
|
0 |
Andersen;
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156 |
|
Boutons are located
approximately every 4 µ along the CA3 axons, but boutons are distributed
unevenly. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
Estimates of the total number of
synapses formed by a single axon in the ipsilateral hippocampus range from
15,000 to 60,000. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
A subset of CA3 axon boutons
contacts interneurons. |
|
0 |
Andersen;
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156 |
|
As in CA1, CA3 pyramidal
cell-to-interneuron synapses are powerful enough that a single axon is
capable of producing an action potential in postsynaptic interneurons. |
|
0 |
Andersen;
Hippocampus Book |
156 |
|
A small number of CA3 neurons
(~20%) may make multiple synapses on a single CA1 cell. |
|
0 |
Andersen;
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156 |
|
Although bursting occurs in CA1
pyramidal neurons, bursting is more prominent in CA3, and is considered a hallmark feature of CA3 pyramidal neurons. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
Bursts in CA3 neurons typically comprise several action
potentials riding atop a depolarizing waveform. |
|
1 |
Andersen;
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157 |
|
Each burst is an "all or nothing" event lasting approximately 30 to 50 ms, with the frequency of action potentials in the range of 100 to 300 Hz. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
Bursts can be triggered in
several ways in CA3 neurons. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
One mechanism for burst
generation is entirely intrinsic to the neuron and does not require synaptic
connectivity. |
|
0 |
Andersen;
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157 |
|
In some cases bursts occur
spontaneously. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
The most robust bursts are generated in CA3 neurons when the entire network becomes synchronously active, usually in response
to suppression of synaptic inhibition. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
The entire
network becoming synchronously
active is a hallmark of seizure activity in cortical networks. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
Intrinsic
conductance can generate
bursts that are likely to serve as an important signals in a normally functioning network, whereas massive,
synchronous glutamate release contributes to synchronous bursting
during hippocampal seizures. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
Because CA3
pyramidal neurons generate seizures, they have been
extensively studied as the possible pacemakers of interictal epileptiform
activity in a variety of animal models
of electrographic seizures. |
|
0 |
Andersen;
Hippocampus Book |
157 |
|
There is good evidence that
network bursts are terminated by depletion of glutamate-containing synaptic
vesicles during the giant EPSPs that drive the PDS. |
|
0 |
Andersen;
Hippocampus Book |
158 |
|
Passive models CA3 pyramidal
neurons predict large attenuation of EPSPs between the dendrites and the
soma. |
|
1 |
Andersen;
Hippocampus Book |
158 |
|
Dendritic attenuation is likely
to be overcome, at least in part, by the presence of voltage-gated
conductances in the dendrites. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Because CA3 pyramidal cells lack
a large primary apical dendrite such as found in CA1, studies of dendritic
excitability and ion channels in CA3 dendrites have lagged behind those in
CA1. |
|
1 |
Andersen;
Hippocampus Book |
159 |
|
Little is known about the
identities and properties of specific ion conductance is in the dendrites of
CA3 pyramidal neurons. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Although much of what we know
about dendritic excitability in CA3 has been inferred from a relatively small
number of dendritic recordings and calcium imaging, some interesting computer
models have been developed for CA3 neurons. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
The subiculum plays an important role in the
hippocampal formation, as it receives convergent input from numerous sources and constitutes a
major output of the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
The pronounced tendency of
neurons in the subiculum region to fire bursts of action potentials has led
to considerable interest in understanding the cell physiology of these
neurons. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Almost all principal neurons in
the subiculum have a typical pyramidal morphology, with apical dendrites
extending into the molecular layer. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
As in CA1, the dendrites of
subiculum pyramidal neurons are studied with spines. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Little is known about the
distribution of the numerous cortical and subcortical inputs to the dendritic
trees of subiculum pyramidal neurons. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Two of the most prominent inputs
to subiculum include topological projections from CA1 and entorhinal cortex. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Among the subcortical structures
projecting to the subiculum are the thalamic nucleus and weak cholinergic
projections from the septal nucleus. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Modulatory inputs from the
brainstem also innervate the subiculum, including the locus coeruleus
(noradrenergic), ventral tegmental area (dopaminergic), and raphe nuclei
(serotonergic). |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
In addition to a direct input
from the entorhinal cortex, the subiculum receives inputs from many of the
same cortical areas that project to the entorhinal cortex. |
|
0 |
Andersen;
Hippocampus Book |
159 |
|
Almost nothing is known about
the inhibitory interneurons and their targeting of pyramidal neurons in the
subiculum. |
|
0 |
Andersen;
Hippocampus Book |
160 |
|
Axons of the subiculum pyramidal
neurons collateralize extensively in the subiculum as well as projecting out
of the subiculum. |
|
1 |
Andersen;
Hippocampus Book |
160 |
|
Pyramidal neurons with deeper
cell bodies in the subiculum tend to form vertically oriented columns of
local collaterals, whereas superficial pyramidal neurons exhibit a greater
horizontal spread (towards CA1 and EC) in their local axon collaterals. |
|
0 |
Andersen;
Hippocampus Book |
160 |
|
Projecting axon collaterals of
the subiculum target a number of cortical and subcortical structures. They do
not project back to CA1 but do project to the entorhinal cortex and the pre-
and parasubiculum. |
|
0 |
Andersen;
Hippocampus Book |
160 |
|
Connections are organized such
that subiculum projects back to the same regions of the entorhinal cortex
from which it receives input |
|
0 |
Andersen;
Hippocampus Book |
160 |
|
Among the other numerous targets
of the subiculum are the medial prefrontal cortex, anterior olfactory
nucleus, septal complex, mammilary nuclei, nucleus accumbens, olfactory
tubercle, several thalamic nuclei, and the amygdaloid complex. |
|
0 |
Andersen;
Hippocampus Book |
160 |
|
A prominent feature of the
firing patterns of subicular pyramidal neurons is action potential bursting. |
|
0 |
Andersen;
Hippocampus Book |
160 |
|
Bursting is much more prominent
in this a big killer and than in CA1. |
|
0 |
Andersen;
Hippocampus Book |
160 |
|
Pyramidal cells in the subiculum
have been shown to fall into two broad physiological categories: bursting
cells and regular-spiking cells. |
|
0 |
Andersen;
Hippocampus Book |
161 |
|
It has been shown that bursting
cells project preferentially to the presubiculum and parasubiculum, whereas
regular-spiking cells project preferentially to the entorhinal cortex. |
|
1 |
Andersen;
Hippocampus Book |
162 |
|
Another important feature of
pyramidal neurons in the subiculum is their ability to generate subthreshold
membrane potential oscillations in the theta frequency range of 5 to 9 Hz. |
|
1 |
Andersen;
Hippocampus Book |
162 |
|
Subicular pyramidal cells also
participate in synaptically mediated oscillations in the gamma frequency
range of 20 to 50 Hz. |
|
0 |
Andersen;
Hippocampus Book |
162 |
|
Bursting neurons in subiculum
fire doublets of action potentials during oscillations, which likely promote
the spread of network activity in the gamma range. |
|
0 |
Andersen;
Hippocampus Book |
162 |
|
Dentate Granule Neurons |
|
0 |
Andersen;
Hippocampus Book |
162 |
|
The main cell type of the
dentate gyrus is the granule cell. |
|
0 |
Andersen;
Hippocampus Book |
162 |
|
The granule cells neurons of the
dentate gyrus have been studied extensively, in part because they were the
first to be shown to exhibit LTP and in part because they receive spatially
segregated synaptic inputs on different regions of their dendrites. |
|
0 |
Andersen;
Hippocampus Book |
162 |
|
Granule cells were the first
cell type in which it was shown that mRNA could be translated into proteins
in dendrites, which has significant implications for plasticity and learning. |
|
0 |
Andersen;
Hippocampus Book |
163 |
|
The granule cells of the dentate
gyrus comprise a small, ovoid cell body with a single, approximately comical
dendritic tree. |
|
1 |
Andersen;
Hippocampus Book |
163 |
|
The granule cells lie in densely
packed, columnar stacks beneath the relatively cell-free molecular layer and
cell-rich polymorphic layer. |
|
0 |
Andersen;
Hippocampus Book |
163 |
|
Granule cell dendrites all
extended into the molecular layer and terminate near the hippocampal fissure. |
|
0 |
Andersen;
Hippocampus Book |
163 |
|
Like pyramidal neurons, the
dendrites of granule cells are heavily studied with spines. |
|
0 |
Andersen;
Hippocampus Book |
163 |
|
The available data suggest that
granule cells have between 5630 and 3600 spines. |
|
0 |
Andersen;
Hippocampus Book |
163 |
|
Dentate granule cell dendritic
morphology, spines, and synaptic inputs and outputs. (diagram) |
|
0 |
Andersen;
Hippocampus Book |
178 |
|
Inhibitory Interneuron Diversity (diagram) |
|
15 |
Andersen;
Hippocampus Book |
179 |
|
Morphological Classification of Hippocampal Interneurons (table) |
|
1 |
Andersen;
Hippocampus Book |
179 |
|
All local
circuit inhibitory
interneurons synthesize and release GABA as their primary neurotransmitter. |
|
0 |
Andersen;
Hippocampus Book |
179 |
|
Anatomically, interneurons represent one of the most diverse populations in the mammalian CNS. |
|
0 |
Andersen;
Hippocampus Book |
179 |
|
Inability to classify
interneurons neatly into functional anatomical sub-populations. |
|
0 |
Andersen;
Hippocampus Book |
179 |
|
Mapping of axonal arbors to
specific domains across the dendritic trees of their targets and the position
the dendrites in specific hippocampal subfields have provided important clues
to specific functional roles played by various interneurons subtypes. |
|
0 |
Andersen;
Hippocampus Book |
179 |
|
Interneurons with axons that
innervate either pyramidal cell soma or axon initial segments (basket cells,
chandelier cells, axo-axonic cells) almost certainly regulate the local
generation of action potentials. |
|
0 |
Andersen;
Hippocampus Book |
179 |
|
Inhibition arriving at dendritic
locations likely has little direct influence over somatic action potential
generation but may strongly influence local dendritic integration, shunt
excitatory inputs on their way to the soma, or regulate dendritic spike initiation
and/or propagation. |
|
0 |
Andersen;
Hippocampus Book |
179 |
|
Perhaps one of the most useful characterizations of interneuron subtypes has been based on neurochemical content. |
|
0 |
Andersen;
Hippocampus Book |
179 |
|
Neurochemically identical cells can have surprisingly different functional properties. |
|
0 |
Andersen;
Hippocampus Book |
180 |
|
Characterization of interneurons
based on function has proven to be problematic. The classic subdivisions were
originally based solely on action potential firing patterns (e.g. fast
spiking versus regular spiking). |
|
1 |
Andersen;
Hippocampus Book |
180 |
|
Action potential generation
results from the combined activity of numerous voltage-gated channels, with
each channel type potentially having a unique expression pattern throughout
the interneuron subpopulation that imparts subtle characteristics to action
potential firing. |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
Neurochemical
markers used to classify hippocampal interneurons (table) |
|
1 |
Andersen;
Hippocampus Book |
181 |
|
Subdivisions of interneurons
based on responses to neuromodulators, properties of intrinsic currents and
conductances, or expressions of ligand-gated channels have all had limited
success. |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
Interneurons are excited or
inhibited by a bewildering number of combinations of modulators, and when
these properties are mapped onto their respective anatomical properties, a
staggering number of subpopulations may exist. |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
The list of
synapses that
demonstrate facilitation or depression has become increasingly lengthy. |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
CA1
pyramidal cell-mediated feedback excitation of interneurons. |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
Whether a particular synapse
demonstrates short-term depression or facilitation may be developmentally
regulated. |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
Dendritic Morphology |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
Despite representing only ~10%
of the total hippocampal neuron population, inhibitory interneurons have
highly variable morphologies even within distinct subpopulations. |
|
0 |
Andersen;
Hippocampus Book |
181 |
|
Cells of a
given neurochemical
subclass can have dendrites that are organized in a widely heterogeneous orientation. |
|
0 |
Andersen;
Hippocampus Book |
182 |
|
Inhibitory interneuron neurochemistry in dendritic morphology. A large difference in the absolute
and relative numbers of excitatory and inhibitory synapses terminating on dendrites. (diagram) |
|
1 |
Andersen;
Hippocampus Book |
182 |
|
Arguably the largest of all the
inhibitory interneuron subpopulations, the PV-containing, fast-spiking basket
cells are found throughout the hippocampal formation. |
|
0 |
Andersen;
Hippocampus Book |
182 |
|
Among interneurons,
PV-containing cells have the most elaborate dendrites, which on average
measure >4 mm in their full extent. |
|
0 |
Andersen;
Hippocampus Book |
182 |
|
PV-containing interneurons have
on average 5 primary dendrites that arise from the soma and run radiantly
through the stratum oriens or through the stratum radiatum into the stratum
lacunosum-moleculare making infrequent branches. |
|
0 |
Andersen;
Hippocampus Book |
182 |
|
Although PV-containing
interneurons have the largest dendritic tree of all interneuron types, these
cells demonstrate large variation in individual cell size, with a more than
twofold variation in the range of dendritic length. |
|
0 |
Andersen;
Hippocampus Book |
183 |
|
One special class of the inhibitory interneurons project out of the hippocampus to the medial septum. |
|
1 |
Andersen;
Hippocampus Book |
183 |
|
CR-containing interneurons can
be subdivided into at least two classes based on morphology: a spiny type in
a spine-free type. In the CA1 subfield only spine-free CR-containing
interneurons are found, whereas both classes are found in CA3. |
|
0 |
Andersen;
Hippocampus Book |
183 |
|
Dendritic Spines |
|
0 |
Andersen;
Hippocampus Book |
183 |
|
The conspicuous
absence of dendritic spines on most interneuron types undoubtably has a major impact on their computational properties. |
|
0 |
Andersen;
Hippocampus Book |
183 |
|
Some well-characterized interneurons are covered densely by dendritic spines. |
|
0 |
Andersen;
Hippocampus Book |
184 |
|
When present, spines on interneurons show profound differences from their
counterparts on pyramidal neurons. |
|
1 |
Andersen;
Hippocampus Book |
184 |
|
The spines of interneurons are covered by numerous excitatory synaptic
boutons. |
|
0 |
Andersen;
Hippocampus Book |
184 |
|
Most pyramidal
cell spines have only
one bouton
occasionally two. |
|
0 |
Andersen;
Hippocampus Book |
184 |
|
The large
number of excitatory
spines on interneurons spines raises the possibility
that spines of interneurons serve to increase the synaptic surface area
and do not function as a compartmentalization device as in pyramidal cells. |
|
0 |
Andersen;
Hippocampus Book |
184 |
|
Excitatory and Inhibitory
Synapses |
|
0 |
Andersen;
Hippocampus Book |
184 |
|
Within the hippocampal
circuit, interneurons receive afferent excitatory input from a number of intrinsic and extrinsic sources. |
|
0 |
Andersen;
Hippocampus Book |
184 |
|
In addition to their inhibitory inputs onto principal cells, interneurons provide inhibitory input to other interneurons. |
|
0 |
Andersen;
Hippocampus Book |
184 |
|
In contrast to our appreciation
of inhibitory transmission
onto principal cells, much less is known regarding the nature
of inhibition between interneuron subpopulations. |
|
0 |
Andersen;
Hippocampus Book |
185 |
|
In addition to excitatory
glutamatergic innervation, many neurons also express muscarinic and nicotinic
receptors and receive cholinergic input from the medial septum. |
|
1 |
Andersen;
Hippocampus Book |
185 |
|
For interneuron inputs, there is
evidence for noradrenergic input from the locus coeruleus, serotonergic input
from the raphe nucleus, and histaminergic input from the supramammillary
nucleus. |
|
0 |
Andersen;
Hippocampus Book |
185 |
|
Although the roles of many of
the neuromodulatory systems are poorly understood, several studies have
elucidated the roles of a few of the modulators. |
|
0 |
Andersen;
Hippocampus Book |
185 |
|
Axonal arborization of local-circuit inhibitory interneurons constitutes another diverse feature of their anatomy. |
|
0 |
Andersen;
Hippocampus Book |
185 |
|
Each cell type or subclass of inhibitory interneuron innervates distinct subcellular compartments
of each of their targets. |
|
0 |
Andersen;
Hippocampus Book |
185 |
|
The arrangement of axonal distribution predicts the role each
interneuron plays in influencing activity of the postsynaptic cell. |
|
0 |
Andersen;
Hippocampus Book |
185 |
|
Fast-spiking basket cells typically have axons that emerge from either the soma or a proximal dendrite. The axon makes collaterals that extend into the stratum radiatum but primarily arborize throughout the pyramidal cell layer. |
|
0 |
Andersen;
Hippocampus Book |
185 |
|
Chandelier cells or axo-axonic
cells of the dentate gyrus and hippocampus are so named because of the
appearance of their axonal arborization. |
|
0 |
Andersen;
Hippocampus Book |
203 |
|
Synaptic Function |
|
18 |
Andersen;
Hippocampus Book |
203 |
|
Sherrington
coined the term "synapse" (from the Greek "hold together"). |
|
0 |
Andersen;
Hippocampus Book |
208 |
|
Voltage-Clamp Techniques |
|
5 |
Andersen;
Hippocampus Book |
209 |
|
The conventional view of
synaptic function -- originating from the studies of Katz and coworkers at
the neuromuscular junction -- is that transmission is quantized. |
|
1 |
Andersen;
Hippocampus Book |
210 |
|
Short-term Plasticity |
|
1 |
Andersen;
Hippocampus Book |
210 |
|
Synapses
show numerous forms of memory of their activation history. |
|
0 |
Andersen;
Hippocampus Book |
210 |
|
The synaptic
plasticity of long
term potentiation and depression, LTP and
LTD, persist for
hours if not longer. |
|
0 |
Andersen;
Hippocampus Book |
210 |
|
Other forms of
use-dependent plasticity last up to a few minutes and may play an important role in the second-to-second traffic of information through synapses. |
|
0 |
Andersen;
Hippocampus Book |
210 |
|
Increases and decreases in
translation -- facilitation, obligation, and potentiation for increases; and
depression for decreases. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
Facilitation
describes the enhancement of transmission frequently seen following a preceding action potential. |
|
1 |
Andersen;
Hippocampus Book |
211 |
|
Augmentation refers to a gradual
increase in synaptic strength with repeated stimulation. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
Potentiation
requires a high-frequency train of stimuli for its induction and persist
for up to a few minutes
after the end of the train. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
Many synapses do not show potentiation
phenomenon and, instead,
depress when repeatedly
stimulated. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
The distinct
patterns of short-term
plasticity result
from a large number of processes occurring principally in the presynaptic
terminals. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
Postsynaptic mechanisms can also contribute to short-term plasticity. Polarizing synaptic potentials can summate, leading to
activation of regenerative currents in postsynaptic dendrite. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
Because principal
neurons frequently discharge in bursts of action potentials, the degree of
postsynaptic facilitation or depression during such bursts may contain
much of the information transmitted through the
network. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
It has been argued that lasting
changes in short-term plasticity are of greater importance for information
encoding than synaptic strength per se. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
Because short-term plasticity is
mediated predominantly through use-dependent alteration in release
probability, the information contained in a facilitating or depressing burst
is inevitably corrupted by the stochastic nature of transmitter release. |
|
0 |
Andersen;
Hippocampus Book |
211 |
|
The main excitatory transmitter in the hippocampus, as elsewhere in the mammalian CNS, is glutamate. |
|
0 |
Andersen;
Hippocampus Book |
212 |
|
Glutamate-glutamine cycle
(diagram) |
|
1 |
Andersen;
Hippocampus Book |
213 |
|
Most excitatory hippocampus synapses are mediated
by AMPA and NMDA receptors, which have strikingly different biophysical and pharmacological properties. |
|
1 |
Andersen;
Hippocampus Book |
213 |
|
AMPA receptors require a rapid pulse of glutamate in excess of approximately 100
µmol to open. |
|
0 |
Andersen;
Hippocampus Book |
213 |
|
AMPA receptors show a rapid
rise time (100-600 µs
at physiological temperature). This reflects both very
fast binding kinetics and a high opening probability. |
|
0 |
Andersen;
Hippocampus Book |
213 |
|
AMPA receptors deactivate rapidly following clearance of synaptic glutamate (with a time constant of 2.3-3.0 ms). |
|
0 |
Andersen;
Hippocampus Book |
215 |
|
NMDA receptors show many
striking properties that mark them out as quite different from AMPA and
kainate receptors. |
|
2 |
Andersen;
Hippocampus Book |
215 |
|
NMDA receptors have very slow kinetics and can continue to mediate an ion flux
for several hundreds of milliseconds after the glutamate pulse has
terminated
(activation time constant is approximately 7 ms; deactivation time constants are approximately 200 ms
and 1-3 seconds). |
|
0 |
Andersen;
Hippocampus Book |
216 |
|
Metabotropic receptors contain seven transmembrane
segments and are coupled to nucleotide-binding G proteins, which mediate most of their actions. |
|
1 |
Andersen;
Hippocampus Book |
218 |
|
GABA receptors are divided into ionotropic (GABAA) and metabotropic (GABAB) receptors. |
|
2 |
Andersen;
Hippocampus Book |
219 |
|
GABA cycle.
The inhibitory neurotransmitter GABA is synthesized from glutamate via the action of two enzymes. (diagram) |
|
1 |
Andersen;
Hippocampus Book |
220 |
|
In comparison with glutamate and GABA, other
neurotransmitters are
present at far fewer synapses. |
|
1 |
Andersen;
Hippocampus Book |
221 |
|
Among other small
molecules that act as neurotransmitters are the monoamines noradrenaline
(norepinephrine), dopamine (DA), serotonin (5-HT), and histamine. |
|
1 |
Andersen;
Hippocampus Book |
221 |
|
The hippocampus receives dopaminergic projections from both the substantia nigra and the ventral tegmental area. |
|
0 |
Andersen;
Hippocampus Book |
221 |
|
It is possible that the main
role of dopamine is to modulate synaptic transmission. |
|
0 |
Andersen;
Hippocampus Book |
222 |
|
A large number of peptides have
also been shown to exist in axonal varicosities and to bind to specific
receptors in the hippocampus. |
|
1 |
Andersen;
Hippocampus Book |
222 |
|
Hippocampal synapses usually occur at hippocampal varicosities (the widely used term
"terminal"
is thus misleading). |
|
0 |
Andersen;
Hippocampus Book |
222 |
|
Varicosities
occur at irregular intervals along many
axons. |
|
0 |
Andersen;
Hippocampus Book |
223 |
|
The most
abundant type of synapse in the hippocampus is the small glutamatergic synapse made on dendritic spines. |
|
1 |
Andersen;
Hippocampus Book |
225 |
|
The average release probability
at Schaffer collateral-CA1 pyramidal neuron synapses is probably less than
50%, although it is highly variable from synapse to synapse. |
|
2 |
Andersen;
Hippocampus Book |
225 |
|
Even though a pyramidal neuron
has 10,000 to 30,000 spine synapses, it has been estimated that only 16 to 26
need to fire synchronously to bring it to action potential threshold. |
|
0 |
Andersen;
Hippocampus Book |
225 |
|
Because the dendrites of CA1 pyramidal neurons can extend up to 500 µ from the
soma, an
important question is whether distal synapses are as effective as proximal ones. |
|
0 |
Andersen;
Hippocampus Book |
225 |
|
Dentate granule cells are much
smaller and have fewer total spines than pyramidal neurons, although they
have the same spine density per unit length of dendrite. |
|
0 |
Andersen;
Hippocampus Book |
226 |
|
Mossy fibers are the fan
unmyelinated axons of dentate granule cells. |
|
1 |
Andersen;
Hippocampus Book |
229 |
|
GABAergic inhibition of
principal neurons plays an essential role in regulating the transmission of
information through the hippocampal formation. |
|
3 |
Andersen;
Hippocampus Book |
230 |
|
Most GABAergic
synapses show marked
depression with
repetitive activity at moderate
frequencies. |
|
1 |
Andersen;
Hippocampus Book |
243 |
|
Molecular Mechanisms of Synaptic
Function in the Hippocampus |
|
13 |
Andersen;
Hippocampus Book |
243 |
|
In the hippocampus, excitatory
(also termed principle or pyramidal) neurons, the basic working units of the
mammalian central nervous system (CNS), form a highly organized three-layer
circuit. |
|
0 |
Andersen;
Hippocampus Book |
244 |
|
Synaptic vesicles are kept in
two spatially and functionally distinct pools: the reserve pool and the
readily releasable pool. |
|
1 |
Andersen;
Hippocampus Book |
244 |
|
Synaptic vesicles, after their
mobilization toward the active zone, undergo a number of trafficking steps
before achieving a state in which they are ready to fuse with the presynaptic
plasma membrane, the so call readily releasable state. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Local Circuits |
|
53 |
Andersen;
Hippocampus Book |
297 |
|
Local circuits play a critical
role in determining the pattern of output from discrete brain regions
receiving multiple inputs over time. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Individual neurons act as
integrators of multiple app for inputs and/or coincidence detectors. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Hippocampal neurons are divided into two major
classes: principal cells and interneurons. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Interneurons are considerably
less abundant (less than 10%) than spiny principal neurons such as granule
and mossy cells and it didn't take gyrus and Brett pyramidal neurons in the
CA1 and CA3 areas. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Despite their relatively small
numbers, there is an astonishing variety of interneuron classes. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
In addition to highlighting the
diversity of interneuronal subtypes, research data has revealed an equally
bewildering complexity of interneuronal organization. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Certain classes of hippocampal
interneurons establish a commissural axon collateral or even project to
extrahippocampal targets. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Virtually all excitatory
hippocampal projection neurons have a local axonal arbor and could be
considered local-circuit neurons. |
|
0 |
Andersen;
Hippocampus Book |
297 |
|
Hippocampal interneurons can be
defined operationally as GABAergic non-principal cells. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Input Specificity of Extrinsic
Afferents |
|
1 |
Andersen;
Hippocampus Book |
298 |
|
All hippocampal subfields
received an abundance of extrinsic afferents, which can be grouped into three
broad classes: (1) glutamatergic inputs, (2) septo-hippocampal GABAergic
projection, (3) several pathways from brain stem and forebrain nuclei. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Glutamatergic inputs (e.g.,
originating in entorhinal cortex and other ipsilateral and contralateral
hippocampal subregions. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Brain stem and four brain nuclei
releasing neurotransmitters that act as neuromodulators, among them
acetylcholine, dopamine, serotonin, and noradrenaline (norepinephrine). |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Excitatory, glutamatergic
afferent pathways show a high degree of lamina selectivity. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
The lamina specificity of inputs
can have powerful effects on shaping output from the target population. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Hippocampal principal cells show
a marked distribution pattern of intrinsic conductance. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Conduct and set favors for
semantic responses is preferentially located on this till dendritic
compartments. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
The distribution of conductance
has profound effects on integrative and coincidence-detection abilities. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
The high degree of the laminar
specificity of glutamatergic input to hippocampal subregions is also
accompanied by specificity in interneuron targets. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
The architecture provides
specific target region responses to specific inputs at both the cellular
compartment level and local circuit levels. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Cholinergic axons branched
profusely and all hippocampal layers and establish synaptic contacts with
both principal cells and interneurons. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Noradrenergic afferents from the
locus coeruleus do not appear to have a particular target preference but I
particularly dance in areas that receive mossy fiber input. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Serotoninergic-hippocampal projection also shows
a lack of specificity. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Although most
hippocampal neurons express dopamine receptors, mesohippocampal projections are predominately to area CA1. |
|
0 |
Andersen;
Hippocampus Book |
298 |
|
Noradrenergic
fibers from the locus
coeruleus project mainly to the dentate gyrus. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Patterns of Local Circuit
Connectivity |
|
1 |
Andersen;
Hippocampus Book |
299 |
|
Feedforward inhibition serves to impose a temporal framework on a target area on the basis of inputs received. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
The delay associated with an
additional synapse ensures that a feedforward inhibitory synaptic pulse does
not impinge on the initial, direct extrinsic synaptic event in principal
neurons. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Some anti-neurons receive and
put only from extrinsic afferents and can thus possess a paid only in
feedforward inhibition. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Feedforward inhibition can account for most of the input from extrinsic sources. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Mossy fiber axons in the area
CA3 make roughly 10 times as many contacts with CA3 interneurons as with the
far more numerous CA3 principal cells. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
When principal
neurons fire, a number of interneurons receives synaptic excitation. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Interneurons
target local
principal cells, thus providing a feedback inhibitory circuit. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Local feedback circuits can account for most of the local output from principal neurons. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
In area CA1, excitatory neurons have a strong preference for interneurons as targets. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Generation of the output action
potential from a hippocampal subregion is followed rapidly by period of
marked local inhibition. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Many interneurons can be
involved in both feedforward and feedback inhibition, providing a functional
link between afferent input patterns in any resulting output from the target
area. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Recurrent
connections are not
limited to interneurons. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
Recurrent excitation is also
seen in a hippocampal local circuits. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
In the hippocampus, they are
probably few, if any, neurons without local axon collaterals synapse thing
own neighboring neurons. |
|
0 |
Andersen;
Hippocampus Book |
299 |
|
In general, principal neurons
were he currently excited other local (or neighboring) principal neurons as
well as interneurons. |
|
0 |
Andersen;
Hippocampus Book |
300 |
|
Basic Local Circuit Interactions
(diagram) |
|
1 |
Andersen;
Hippocampus Book |
301 |
|
Dentate Gyrus |
|
1 |
Andersen;
Hippocampus Book |
301 |
|
Granule cells
are the principal neuronal type of the dentate gyrus. |
|
0 |
Andersen;
Hippocampus Book |
301 |
|
The sole afferent projection of
granule cells of the dentate gyrus is that mossy fiber pathway, forming the
second link of the tri-synaptic loop targeting the CA3 pyramidal cells. |
|
0 |
Andersen;
Hippocampus Book |
301 |
|
Within the dentate gyrus,
granule cells may function as elements in circuits generating feedforward and
feedback inhibition as well as recurrent excitatory circuits. |
|
0 |
Andersen;
Hippocampus Book |
302 |
|
Basic organization of
interneuron output fields in the dentate gyrus (diagram) |
|
1 |
Andersen;
Hippocampus Book |
305 |
|
Area CA3 and CA1 |
|
3 |
Andersen;
Hippocampus Book |
305 |
|
In the classic hippocampal
tri-synaptic circuit, activity is projected from the dentate gyrus to CA3 and
then from CA3 via Schaffer collaterals to CA1. |
|
0 |
Andersen;
Hippocampus Book |
305 |
|
Direct input to area CA3 and CA1
also originate from the entorhinal cortex. |
|
0 |
Andersen;
Hippocampus Book |
305 |
|
The principal neurons in the
hippocampal subfields constitute a relatively homogeneous population of
glutamate-releasing pyramid-shaped neurons. |
|
0 |
Andersen;
Hippocampus Book |
305 |
|
In the CA1 and CA3 areas
pyramidal neurons bear numerous spines, with estimates being as high as
30,000. |
|
0 |
Andersen;
Hippocampus Book |
305 |
|
Most of these spines receive a
single excitatory synapse. |
|
0 |
Andersen;
Hippocampus Book |
305 |
|
Although all pyramidal neurons
have a local axonal arbor, most excitatory synapses in the hippocampal
subfields are of extraneous origin, arriving from a multitude of sources. |
|
0 |
Andersen;
Hippocampus Book |
306 |
|
The excitatory synapse sources
for pyramidal neurons include -- a different hippocampal subfield, the
contralateral hippocampus, the entorhinal cortex, the submammillary body, and
thalamic nuclei. |
|
1 |
Andersen;
Hippocampus Book |
321 |
|
Structural Plasticity |
|
15 |
Andersen;
Hippocampus Book |
321 |
|
The hippocampus
formation has been described as a relatively late-developing brain region. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
The hippocampus appears to undergo dynamic
modifications continually in the form of dendritic extension and retraction as well as synaptic formation and elimination. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
Perhaps the most basic of all
structural changes is the addition of new neurons, a phenomenon known as
neurogenesis. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
Neurogenesis is now recognized
to be a substantial process in some regions of the adult brain. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
They didn't take gyrus of the
rat adds thousands of new neurons every day throughout adulthood. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
The incorporation of new neurons
into pre-existing second straight results in a cascade of structural changes
that further rate increase the structural plasticity of the region. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
New neurons elaborate axons and
dendrites and undergo synaptogenesis. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
Progressive events of
neurodegenerative in hippocampus are typically followed by a series and
regressive phenomena, such as cell death, which likely involves process
retraction and synapse of elimination. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
New neurons
are formed in the dentate
gyrus throughout life. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
Modulation
of neurogenesis in
the dentate gyrus by hormones and by experience. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
Dendritic and Synaptic
Plasticity and a Hippocampal Formation |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
Hippocampus
is a region with a large degree of structural
plasticity. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
Define structure, and sometimes
even the gross structure of the hippocampal formation is constantly changing
under normal conditions. |
|
0 |
Andersen;
Hippocampus Book |
321 |
|
The hippocampal formation is a
dynamic area whose synapses and dendrites are undergoing continuous
rearrangement. |
|
0 |
Andersen;
Hippocampus Book |
322 |
|
Hormones and Dendritic
Architecture |
|
1 |
Andersen;
Hippocampus Book |
322 |
|
High levels of circulating
glucocorticoids have been associated with atrophy of dendrites in the CA3
region. |
|
0 |
Andersen;
Hippocampus Book |
322 |
|
Dendritic architecture and the
hippocampus is influenced by experience. |
|
0 |
Andersen;
Hippocampus Book |
322 |
|
Chronic stress has generally
been shown to have negative effects on the structure of dendrites in the
hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
322 |
|
Environmental Complexity and
Learning |
|
0 |
Andersen;
Hippocampus Book |
322 |
|
Living in enriched environments
increases the size of the dendritic tree, the number of dendritic spines, and
the number of synapses in the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
323 |
|
Structural changes in the
hippocampus as a result of learning, or long term potentiation (LTP), a form
of synaptic plasticity associated with learning. |
|
1 |
Andersen;
Hippocampus Book |
323 |
|
The hippocampal formation has a
remarkable capacity for regeneration after injury. |
|
0 |
Andersen;
Hippocampus Book |
323 |
|
Animal models of disease states
such as epilepsy and stroke. |
|
0 |
Andersen;
Hippocampus Book |
323 |
|
With time following seizure or
stroke, there is considerable structural reorganization in the form of axon
sprouting, which could be viewed as regenerative. |
|
0 |
Andersen;
Hippocampus Book |
323 |
|
The brain is protected from
mechanical injury by the skull and from chemical injury by the blood-brain
barrier. |
|
0 |
Andersen;
Hippocampus Book |
323 |
|
It is not obvious that the
regenerative capacity inherent in the hippocampus evolved to correct brain
damage, particularly that which occurs in old age. |
|
0 |
Andersen;
Hippocampus Book |
324 |
|
Transplantation of neural stem
cells into damaged hippocampus has shown that new neurons can arise from
progenitors, migrate to their appropriate locations where the former
long-distance axons, make appropriate connections, and exhibit normal
electrophysiological responses. |
|
1 |
Andersen;
Hippocampus Book |
324 |
|
Studies suggest that the
hippocampus, particularly of the dentate gyrus, is conducive to the
acceptance of neural stem cell transplants. |
|
0 |
Andersen;
Hippocampus Book |
324 |
|
Conditions such as Alzheimer's
disease, which result in the accumulation of abnormal proteins and the
formation of senile plaques and neurofibrillary tangles, may be less amenable
to transplantation. |
|
0 |
Andersen;
Hippocampus Book |
324 |
|
Although Neurogenesis |
|
0 |
Andersen;
Hippocampus Book |
324 |
|
The dentate
gyrus is one of two
brain regions (other is olfactory bulb) in which adult neurogenesis has been widely
recognized. |
|
0 |
Andersen;
Hippocampus Book |
324 |
|
Adult neurogenesis has been observed in the hippocampus in virtually every mammalian species examined. |
|
0 |
Andersen;
Hippocampus Book |
325 |
|
Adult neurogenesis was rediscovered in the dentate
gyrus and olfactory
bulb during the 1990s and is now a relatively
well-established phenomenon. |
|
1 |
Andersen;
Hippocampus Book |
326 |
|
Hormones and Adult Neurogenesis |
|
1 |
Andersen;
Hippocampus Book |
326 |
|
The hippocampus
formation is known to be richly endowed with hormone receptors. |
|
0 |
Andersen;
Hippocampus Book |
326 |
|
Many cell types in the
hippocampal formation contain hormone receptors and respond to experimental
hormone manipulations during adulthood with dramatic structural changes. |
|
0 |
Andersen;
Hippocampus Book |
326 |
|
Studies have shown that the
production of new neurons in the dentate gyrus is sensitive to the levels of
circulating steroid hormones. |
|
0 |
Andersen;
Hippocampus Book |
326 |
|
Glucocorticoids inhibit the
production of new neurons by decreasing the proliferation of granule cell
precursors. |
|
0 |
Andersen;
Hippocampus Book |
328 |
|
Experienced and Adult
Neurogenesis |
|
2 |
Andersen;
Hippocampus Book |
328 |
|
Environmental experience takes
many forms: sensory and motor experience, changing cognitive demands, and
stress. |
|
0 |
Andersen;
Hippocampus Book |
328 |
|
A major component of the
"fight or flight" reaction is the mobilization of energy stores to
facilitate reaction to the imminent danger. |
|
0 |
Andersen;
Hippocampus Book |
328 |
|
Stress inhibits the production
of new granule cells during development and in adulthood. |
|
0 |
Andersen;
Hippocampus Book |
330 |
|
Physical activity increases cell
pole for ration and ultimately the production of new neurons in the dentate
gyrus of adult rodents. |
|
2 |
Andersen;
Hippocampus Book |
330 |
|
Individual Differences in Adult
Neurogenesis |
|
0 |
Andersen;
Hippocampus Book |
330 |
|
When adult rodents are group
housed in a relatively large, complex and closure, a dominance hierarchy
forms. |
|
0 |
Andersen;
Hippocampus Book |
330 |
|
Dominant animals, characterized
by the amount of offenses or aggressive behavior displayed, have
substantially more new neurons than subordinate animals. |
|
0 |
Andersen;
Hippocampus Book |
331 |
|
Subordinate chickadees make
fewer new cells in the hippocampus than dominant chickadees. |
|
1 |
Andersen;
Hippocampus Book |
331 |
|
Neurogenesis Following Damage |
|
0 |
Andersen;
Hippocampus Book |
331 |
|
Neurogenesis is upregulated in
neurodegenerative conditions such as Alzheimer's disease and Parkinson's
disease. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
Not only are there well known
differences between different cell types, there are also developmental
differences between individual cells of the common cell type. |
|
1 |
Andersen;
Hippocampus Book |
332 |
|
The granule cell layer consists
of neurons ranging in age from hours to years. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
Although many thousands of new
neurons are added to the dentate gyrus every day, this is a relatively small
proportion of the large number of material granule neurons produced during
development and that survive through to adulthood. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
Adult generated neurons are
likely to have structural characteristics that differ from developmentally
generated neurons. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
Adult-generated granule cells
are capable of undergoing rapid structural change, as evidenced by the fact
that they have axons in the distal CA3 within 4 to 10 days at the mitosis. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
Much work is needed to determine
the functional characteristics of new neurons in the dentate gyrus. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
The daily production of
thousands of new granule cells and their incorporation into the existing
circuitry are costly in terms of energy expenditure. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
The continual influx of new
cells provide some aspect of function of the dentate gyrus that cannot be
obtained with a structure comprising mature neurons exclusively. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
The existence of a large pool of
immature neurons in a brain region raises the possibility that these new
cells are important for certain types of learning and memory. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
A widely held view is that the hippocampus formation plays a temporary role in storing new memories. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
Recent, but not remote, memories
for certain information are eliminated by lesioning the hippocampal
formation. |
|
0 |
Andersen;
Hippocampus Book |
332 |
|
Neurons produced during
adulthood might play a role in memory processing for a short time after their
generation. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
New cells might degenerate or
undergo changes in connectivity, gene expression, or both around the time the
hippocampal formation no longer plays a role in the storage of that
particular memory. |
|
1 |
Andersen;
Hippocampus Book |
333 |
|
A temporary role for
adult-generated granule neurons in learning has been suggested in canaries. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Neural network models of memory
formation support a distributed perspective of memory storage. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Examples of factors that enhance
both the number of new neurons and hippocampus-dependent learning are
estrogen treatment and living in an enriched environment. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Situations that decrease the
number of new hippocampus neurons, such as glucocorticoids and stress, are
associated with impaired performance. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Aging is associated with a decline in new cell production in the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Chronic stress has been shown to inhibit
neurogenesis persistently. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Other age-associated
changes dominate hippocampal
function, such as diminished
number of synapses. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
New cells are
likely to require some time for integration into the existing circuitry. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Dendrites
must be grown and functional synaptic
connections formed; axons must grow and find their
targets. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Chronic changes in cell
proliferation are those most likely to have functional consequences. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Acute stress and chronic stress
diminished the proliferation of granule cell precursors in the dentate gyrus. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Acute stress
has been shown (with certain paradigms) to enhance learning, whereas chronic
stress typically impairs learning. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
A direct link between new
neurons and learning remains controversial. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
A research study has shown that
approximately 9000 new cells are produced every day in the rat dentate gyrus. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
If the granule cells produced
during adulthood are functionally different -- less likely to be inhibited by
GABA and more likely to display synaptic plasticity -- they could be
especially influential. |
|
0 |
Andersen;
Hippocampus Book |
333 |
|
Despite the fact that involved
mother of new neurons and learning is plausible, the available evidence
supporting this view is incomplete and mixed. |
|
0 |
Andersen;
Hippocampus Book |
334 |
|
Behavioral changes following
lesions of the hippocampus rarely uncover a learning impairment unless a
large percentage of the total hippocampal formation is destroyed. |
|
1 |
Andersen;
Hippocampus Book |
334 |
|
The hippocampal formation has
been linked functionally to regulation of the HPA
(hypothalamic-pituitary-adrenal) axis. |
|
0 |
Andersen;
Hippocampus Book |
334 |
|
The hippocampus formation is
purported to play a role in limiting the level of circulating glucocorticoids
following stress |
|
0 |
Andersen;
Hippocampus Book |
334 |
|
Prenatal and postnatal stress
have been shown to result in persistent changes in the HPA axis in the form
of inefficient shutoff of the stress response during adulthood. |
|
0 |
Andersen;
Hippocampus Book |
335 |
|
Antidepressants enhance hippocampal neurogenesis. |
|
1 |
Andersen;
Hippocampus Book |
343 |
|
Synaptic Plasticity in the
Hippocampus |
|
8 |
Andersen;
Hippocampus Book |
343 |
|
Of all the properties of
hippocampal synapses, perhaps the most beguiling inconsequential, and
certainly the most enthusiastically studied, is their ability to respond to
specific patterns of activation with long-lasting increases or decreases in
synaptic efficacy. |
|
0 |
Andersen;
Hippocampus Book |
343 |
|
Synaptic plasticity is a property of many, perhaps most, excitatory synapses in the brain. |
|
0 |
Andersen;
Hippocampus Book |
343 |
|
During the period from 1966 to mid-1980s, the major characteristics of LTP, including its persistence, and specificity, and associativity, were established,
the critical role of the NMDA receptor in the induction of LTP identified, and the
first steps taken to link LTP to hippocampus dependent learning. |
|
0 |
Andersen;
Hippocampus Book |
343 |
|
The
cellular event that triggers
the induction of LTP
is the influx of calcium to the activating NMDA receptor. |
|
0 |
Andersen;
Hippocampus Book |
343 |
|
The various
short-term forms of plasticity that hippocampus synapses share with most if not all synapses: paired pulse facilitation and depression and post
tetenic potentiation. |
|
0 |
Andersen;
Hippocampus Book |
343 |
|
The mossy
fiber projection from the granule cells to CA3 pyramidal cells supports a very different form of LTP. |
|
0 |
Andersen;
Hippocampus Book |
344 |
|
The term "synaptic
plasticity" was introduced by the Polish
psychologist Jerry Konorski to describe the persistent,
activity driven changes in synaptic efficacy that he assumed
to be the basis of information storage in the brain. (Konorski, 1948). |
|
1 |
Andersen;
Hippocampus Book |
344 |
|
A formal hypothesis embodying
the idea of synaptic plasticity was advanced by the Canadian psychologist Donald Hebb in 1949. |
|
0 |
Andersen;
Hippocampus Book |
344 |
|
In 1973, long-lasting changes in synaptic efficacy at perforant path granule cell synapses in the hippocampus could be induced by a brief tetanic stimulation
(Bliss and Lomo, 1973). |
|
0 |
Andersen;
Hippocampus Book |
344 |
|
The discovery of what has come
to be known as long term potentiation (LTP) emerged
from experiments that Per Andersen and Lomo,
then a PhD student,
were conducting at the University of Oslo during the mid-1960s on the phenomenon of frequency potentiation in excitatory hippocampal pathways. |
|
0 |
Andersen;
Hippocampus Book |
346 |
|
LTP has revealed that two other
hippocampal pathways: the mossy
fiber projection to CA3 pyramidal cells and the interleaved commissural and Schaffer collateral fibers from CA3 to CA1 pyramidal cells. We refer to these fibers as the Schaffer-commissural projection. |
|
2 |
Andersen;
Hippocampus Book |
346 |
|
The hypothesis that NMDA receptor
activation is required for inducing LTP received further
support in 1986. |
|
0 |
Andersen;
Hippocampus Book |
347 |
|
During the mid-1980s,
LTP gained acceptance as a physiological mechanism underlying the cognitive faculties of learning and memory. |
|
1 |
Andersen;
Hippocampus Book |
347 |
|
Synaptic
transmission at the level of the single synapse is an inherently stochastic
process that can be modulated
by prior activity in the presynaptic or postsynaptic neuron and by a wide
variety of neuromodulators acting both pre- and post-synaptically. |
|
0 |
Andersen;
Hippocampus Book |
352 |
|
A wide range of stimulus
protocols can induce LTP. |
|
5 |
Andersen;
Hippocampus Book |
353 |
|
Time course
of LTP -- Rapid Onset
and Variable Duration |
|
1 |
Andersen;
Hippocampus Book |
353 |
|
Three
distinct temporal components potentiation -- STP, Early LTP, Late LTP |
|
0 |
Andersen;
Hippocampus Book |
353 |
|
A component
of LTP, usually lasting
less than an hour,
referred to a short-term potentiation (STP). |
|
0 |
Andersen;
Hippocampus Book |
353 |
|
STP is NMDA receptor-dependent but depends neither on protein synthesis nor on protein
kinase activity. |
|
0 |
Andersen;
Hippocampus Book |
355 |
|
Associativity -- Induction of LTP Is Influenced by Activity at Other Synapses |
|
2 |
Andersen;
Hippocampus Book |
356 |
|
The requirement for tight coincidence of presynaptic and postsynaptic activity implies a Hebbian induction rule. |
|
1 |
Andersen;
Hippocampus Book |
356 |
|
There is convincing evidence
that the induction of LTP in
the Schaffer-commissural projection in area CA1 is indeed Hebbian in nature. |
|
0 |
Andersen;
Hippocampus Book |
357 |
|
The most remarkable advance in
understanding the cellular mechanisms of LTP
has been elucidation of the role of the NMDA
receptor in its induction. |
|
1 |
Andersen;
Hippocampus Book |
358 |
|
Explicit in Hebb's
postulate is the notion of causality. In a Hebb synapse, an
increase in synaptic weight occurs only when the presynaptic
cell fires shortly
before the postsynaptic
cell. |
|
1 |
Andersen;
Hippocampus Book |
359 |
|
Ca2+ signaling in LTP |
|
1 |
Andersen;
Hippocampus Book |
359 |
|
Ca2+ release from Ca2+ stores contributes to induction of LTP. |
|
0 |
Andersen;
Hippocampus Book |
359 |
|
A major
source of Ca2+ in neurons is via release from intracellular stores. |
|
0 |
Andersen;
Hippocampus Book |
359 |
|
It is accepted that Ca2+ entry directly through the NMDAR channel is a trigger for NMDAR-dependent LTP. |
|
0 |
Andersen;
Hippocampus Book |
373 |
|
Studies of kinases in NMDA receptor-dependent LTP have shown that several kinases are involved but none is
obligatory. |
|
14 |
Andersen;
Hippocampus Book |
377 |
|
Modification of the Existing
Receptors Contributes to LTP |
|
4 |
Andersen;
Hippocampus Book |
379 |
|
Insertion of AMPA receptors
contributes to LTP. |
|
2 |
Andersen;
Hippocampus Book |
383 |
|
Retrograde signaling is required for communication between the postsynaptic site of induction and the presynaptic terminal. |
|
4 |
Andersen;
Hippocampus Book |
384 |
|
Membrane spanning molecules contribute to signaling between presynaptic and postsynaptic sides of the synapse. |
|
1 |
Andersen;
Hippocampus Book |
385 |
|
Cell adhesion molecules (CAM's) comprise
a large class of diverse membrane-spanning
molecules with extracellular
ligand-binding domains that are important for cell recognition during neural development. |
|
1 |
Andersen;
Hippocampus Book |
385 |
|
Cadherins
are an extensive family of cell adhesion molecules with cytoplasmic signaling domains that are linked to the actin
cytoskeleton through two accessory proteins. |
|
0 |
Andersen;
Hippocampus Book |
388 |
|
Transcription and translation of
new mRNAs -- dialogue between Synapse and Nucleus |
|
3 |
Andersen;
Hippocampus Book |
388 |
|
Protein synthesis at both the local and global levels is involved in the conversion of the early to late LTP. |
|
0 |
Andersen;
Hippocampus Book |
388 |
|
A major route for activity-dependent protein synthesis
proceeds via long-range activation of nuclear transcription factors, including members of the CREB
family of proteins, which bind to cAMP response elements (CREs) in
the regulatory regions
of target genes to initiate transcription. |
|
0 |
Andersen;
Hippocampus Book |
388 |
|
The MAP
kinase signaling cascade can be triggered by a
wide variety of stimuli, including extracellular
ligands binding to receptor
tyrosine kinases and G
protein coupled receptors, and by synaptic activity leading to calcium entry through the ionotropic glutamate receptors or
voltage-gated calcium channels. |
|
0 |
Andersen;
Hippocampus Book |
389 |
|
Stimulation
of dopamine receptors can induce late potentiation in an activity
independent manner. |
|
1 |
Andersen;
Hippocampus Book |
389 |
|
Dopamine
receptor activation leads to the upregulation of cAMP and presumptive translocation of activated PKA to the soma, where it can directly phosphorylate CREB on ser133. |
|
0 |
Andersen;
Hippocampus Book |
389 |
|
The nuclear
transcription factor CREB is a target for several kinases. |
|
0 |
Andersen;
Hippocampus Book |
392 |
|
Signaling pathways involved in
the genesis of late LTP (diagram) |
|
3 |
Andersen;
Hippocampus Book |
393 |
|
The duration of a late LTP is regulated by the NMDA receptor. |
|
1 |
Andersen;
Hippocampus Book |
393 |
|
The expression of a late LTP depends on de novo protein synthesis around
the time of induction, give or take a few hours. |
|
0 |
Andersen;
Hippocampus Book |
393 |
|
Structural remodeling and growth of spines can be stimulated by induction of LTP. |
|
0 |
Andersen;
Hippocampus Book |
397 |
|
Alterations
in the cytoskeleton
contribute to the LTP
and LTD. |
|
4 |
Andersen;
Hippocampus Book |
397 |
|
Dendritic spines are not static structures; rather, their shape is determined from moment to moment by the dynamics of the actin cytoskeleton. |
|
0 |
Andersen;
Hippocampus Book |
398 |
|
LTP at Mossy Fiber Synapses |
|
1 |
Andersen;
Hippocampus Book |
398 |
|
LTP takes a
very different form
at the largest synapses
in the hippocampus, indeed among the largest in the mammalian brain -- the synapses made by granule cell axons (the mossy fibers) on CA3 pyramidal cells. |
|
0 |
Andersen;
Hippocampus Book |
403 |
|
Despite its independence of the NMDA receptor, it is evident that
the LTP at mossy fiber synapses requires an increase in
intracellular Ca2+; but whether the critical compartment is a presynaptic
terminal or the postsynaptic spine remains unresolved and may depend on the pattern of the plasticity-inducing stimulation. |
|
5 |
Andersen;
Hippocampus Book |
403 |
|
Increase in
Ca2+ is not achieved by activation of NMDA receptors.
Instead, increases in Ca2+ are achieved by a variety of alternative routes. |
|
0 |
Andersen;
Hippocampus Book |
403 |
|
The long (1 second) trains at
100 Hz that are required to produce robust mossy fiber LTP are not likely to
be mimicked by granule cells in vivo. |
|
0 |
Andersen;
Hippocampus Book |
403 |
|
It remains to be established
whether naturally occurring patterns of granule cell activity lead to LTP at
mossy fiber synapses. |
|
0 |
Andersen;
Hippocampus Book |
475 |
|
Hippocampal Physiology in the
Behaving Animal |
|
72 |
Andersen;
Hippocampus Book |
549 |
|
Functional Role of the Human
Hippocampus |
|
74 |
Andersen;
Hippocampus Book |
549 |
|
The hippocampus is part of a system that plays a critical role in the encoding
and retrieval of long-term memory for facts and events. |
|
0 |
Andersen;
Hippocampus Book |
549 |
|
The hippocampus is vital for "declarative" or "explicit" form of memory but is not involved in other forms of long-term memory, in non-mnemonic aspects of cognition, or in immediate (or "working") memory. |
|
0 |
Andersen;
Hippocampus Book |
549 |
|
Hippocampus involvement in
declarative memory is not permanent but is time-limited. |
|
0 |
Andersen;
Hippocampus Book |
549 |
|
The hippocampal
region "combines and extends" the
processing of adjacent cortical structures that together form the medial temporal lobe memory system. |
|
0 |
Andersen;
Hippocampus Book |
550 |
|
Patient HM |
|
1 |
Andersen;
Hippocampus Book |
562 |
|
The term "priming" refers to a class of implicit
memory tasks that are not
affected by medial temporal lobe damage |
|
12 |
Andersen;
Hippocampus Book |
563 |
|
A second form of priming, known
as conceptual priming, is apparently intact in amnesia. |
|
1 |
Andersen;
Hippocampus Book |
564 |
|
Dissociation between declarative
memory tasks that involve the hippocampus and nondeclarative memory tasks
that do not. |
|
1 |
Andersen;
Hippocampus Book |
565 |
|
H.M.'s
remote memory appeared to be intact in face of both his
profound and impaired ability to learn new information and a profound loss of information that
he had been exposed to for some time prior to his operation. |
|
1 |
Andersen;
Hippocampus Book |
565 |
|
Some form of consolidation occurs by which memories that initially rely on structures in the medial temporal lobe become independent of the medial temporal lobe over time. |
|
0 |
Andersen;
Hippocampus Book |
569 |
|
Associations, Recollections,
Episodes, or Sources |
|
4 |
Andersen;
Hippocampus Book |
569 |
|
A large amount of research of
the human hippocampus has been named at functionally dissociating the role of the hippocampus from the role of adjacent
cortical structures. |
|
0 |
Andersen;
Hippocampus Book |
581 |
|
Theories of Hippocampal Function |
|
12 |
Andersen;
Hippocampus Book |
581 |
|
How memory handles ambiguity,
associated-relations, and context. |
|
0 |
Andersen;
Hippocampus Book |
582 |
|
Contacts,
relations, and
configurations may each help disambiguate conflicting associative relations in which a specific stimulus
occurs. |
|
1 |
Andersen;
Hippocampus Book |
582 |
|
The hippocampus has been implicated in a range of brain functions including
acting as a comparator
to detect novelty. |
|
0 |
Andersen;
Hippocampus Book |
582 |
|
Marr's proposal that distributed associative memory could
be implemented by hippocampal local circuitry. |
|
0 |
Andersen;
Hippocampus Book |
582 |
|
Neural network modeling has
matured to a level of conceptual and mathematical precision. (Rolls and
Treves, 1998) |
|
0 |
Andersen;
Hippocampus Book |
582 |
|
Neural
activity in the hippocampal
formation contributes to episodic memory. |
|
0 |
Andersen;
Hippocampus Book |
582 |
|
Episodic
memory has been variously characterized as remembering the "scenes"
in which events take place. |
|
0 |
Andersen;
Hippocampus Book |
589 |
|
Genomic Sequence Similarity in
Mammals (diagram) |
|
7 |
Andersen;
Hippocampus Book |
591 |
|
Declarative Memory Theory |
|
2 |
Andersen;
Hippocampus Book |
591 |
|
(1) the primary function of the
hippocampal formation is in memory. |
|
0 |
Andersen;
Hippocampus Book |
591 |
|
(2) the role of the hippocampal formation and memory
is selective. It mediates the memory of facts and
events, called Declarative
Memory. |
|
0 |
Andersen;
Hippocampus Book |
591 |
|
(3) the hippocampal formation is
one of a number of structures that comprise a medial temporal lobe memory
system. |
|
0 |
Andersen;
Hippocampus Book |
591 |
|
(4) time-limited: the role of
the hippocampus in memory is time-limited. The hippocampus contributes to a time-dependent systems-level consolidation process such that, once completed, long-term
memory traces are stored
in the cortex and neural
activity in the hippocampus is no longer required for or involved in the recall. |
|
0 |
Andersen;
Hippocampus Book |
592 |
|
Taxonomy of
mammalian memory systems. The scheme was first
introduced my Squire (1987) and has been updated many times since. (diagram) |
|
1 |
Andersen;
Hippocampus Book |
594 |
|
Medial
temporal lobe memory system. Major component of
Squire's of medial temporal lobe memory system. (diagram) |
|
2 |
Andersen;
Hippocampus Book |
595 |
|
System-level
memory consolidation. Pathways between
neocortical areas representing recent events or recently acquired facts.
(diagram) |
|
1 |
Andersen;
Hippocampus Book |
606 |
|
Remote Memory, Retrograde
Amnesia, and the Time Course of Memory Consolidation in Primates |
|
11 |
Andersen;
Hippocampus Book |
616 |
|
Are Fact Memory and Event Memory
Processed by a Common Brain System? |
|
10 |
Andersen;
Hippocampus Book |
616 |
|
Amnesia
patients have a deficit restricted to episodic memory. They cannot remember events for any
length of time, but their factual knowledge about the world and their knowledge
of language are both intact. Semantic memory shows all the appearances of being preserved. |
|
0 |
Andersen;
Hippocampus Book |
616 |
|
The reason amnesia patients display intact semantic memory is because
so much of a person's factual knowledge was acquired years earlier, extending from the years of childhood on through life. Consolidation of such memory
traces would be long completed. |
|
0 |
Andersen;
Hippocampus Book |
616 |
|
An amnesic
patient's failure of event memory often relates to relatively
recent events such as a forgotten conversation of the day before. |
|
0 |
Andersen;
Hippocampus Book |
616 |
|
Most amnesic patients have some
residual episodic memory function. |
|
0 |
Andersen;
Hippocampus Book |
617 |
|
Amnesia is largely exclusive to
episodic memory. |
|
1 |
Andersen;
Hippocampus Book |
617 |
|
Amnesiacs are temporally and
spatially disoriented: forgetting the date and appointments, getting lost,
mislaying their belongings. |
|
0 |
Andersen;
Hippocampus Book |
617 |
|
Success in recalling either a
fact or an event depends only on the "strength" of the traces
established through consolidation. |
|
0 |
Andersen;
Hippocampus Book |
617 |
|
It has been argued that memory for an event requires
access to a hippocampally-based "contextual" trace
(where the event happened) and a prefrontal temporal trace (when the event happened). |
|
0 |
Andersen;
Hippocampus Book |
617 |
|
Retrieval of event memory is a
reconstruction based on both the "where" trace and the
"when" trace, and other information about the event itself, stored
elsewhere in the neocortex. |
|
0 |
Andersen;
Hippocampus Book |
617 |
|
We still do not understand the
precise role of the hippocampus in episodic and semantic memory. |
|
0 |
Andersen;
Hippocampus Book |
617 |
|
Hippocampus and Space: Cognitive
Map Theory of Hippocampus Function |
|
0 |
Andersen;
Hippocampus Book |
617 |
|
"Place cells" in the
hippocampus of freely moving rats. |
|
0 |
Andersen;
Hippocampus Book |
618 |
|
"Cognitive mapping"
dates back to Tolman's classic paper (Tolman, 1948). |
|
1 |
Andersen;
Hippocampus Book |
618 |
|
Cognitive Map Theory |
|
0 |
Andersen;
Hippocampus Book |
618 |
|
(1) Representation: the
vertebrate brain has a neural system that organizes the encoding and
representation of perceive stimuli with respect to an allocentric spatial
framework, or cognitive map. The spatial locations of the landmarks are
stored in this map during exploration. This locale system is in the
hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
618 |
|
(2) Navigation: they locale
system is used for spatial navigation. |
|
0 |
Andersen;
Hippocampus Book |
618 |
|
(3) Evolution and the laws of
learning: spatial mapping evolve as one of the multiple memory systems of the
vertebrate brain with its own distinctive learning rules. |
|
0 |
Andersen;
Hippocampus Book |
618 |
|
(4) Sites of storage: spatial
maps are stored in the hippocampus. They are not consolidated are stored
elsewhere in the brain, although information stored in the hippocampus does
interact with information stored elsewhere for the purpose of guiding navigational
behavior. |
|
0 |
Andersen;
Hippocampus Book |
618 |
|
(5) Extension of the theory to
humans: where is the cognitive map is purely spatial in animals, in sub
serves as storage and recall of linguistic and episodic memories in humans. |
|
0 |
Andersen;
Hippocampus Book |
620 |
|
Development of multiple
single-unit recording ("ensemble recording"). |
|
2 |
Andersen;
Hippocampus Book |
620 |
|
Pyramidal cells acquire their
place feels rapidly, fire in proportion to an animal speed of motion, and
show temporal precision in their phase relation to the hippocampal theta as
animal moves through the cells place field. |
|
0 |
Andersen;
Hippocampus Book |
620 |
|
Place fields represent
probability distributions and do not specify precise locations. |
|
0 |
Andersen;
Hippocampus Book |
620 |
|
The hippocampal formation and
interconnect being structures constitute, in animals, an essentially spatial
system. |
|
0 |
Andersen;
Hippocampus Book |
620 |
|
The relation between location
firing (in pyramidal cells of CA1 and CA3), head-directional firing (in the
presubiculum and anterior thalamus), and movement firing (in the interneurons
of the hippocampus and dentate gyrus) is poorly understood. |
|
0 |
Andersen;
Hippocampus Book |
620 |
|
Spatial mapping has evolved in
response to specific environmental demands, and constitute one of the
multiple memory system of the vertebrate brain. |
|
0 |
Andersen;
Hippocampus Book |
620 |
|
Cache recovery in passerine
birds, homing in pigeons, territory size and mapping systems in small mammals
and other aspects of naturalistic spatial behavior. |
|
0 |
Andersen;
Hippocampus Book |
621 |
|
The bulk of the work addressing
the cognitive map theory has been conducted with the laboratory rat. |
|
1 |
Andersen;
Hippocampus Book |
621 |
|
The relevance of the cognitive
map theory of hippocampal function extended to human semantic memory and,
specifically, the way in which spatial relations are fundamental to certain
linguistic prepositions that reflect a knowledge of relations (e.g. "beside," "near," "above"). |
|
0 |
Andersen;
Hippocampus Book |
622 |
|
Space is not a sensory modality.
We do not have sensory organs for space. |
|
1 |
Andersen;
Hippocampus Book |
622 |
|
Space is a construct of mental
processing. |
|
0 |
Andersen;
Hippocampus Book |
642 |
|
Homing Pigeons Reveal
Hippocampus-dependent and Hippocampus-independent Components of Navigation |
|
20 |
Andersen;
Hippocampus Book |
650 |
|
Storage and Consolidation of
Spatial Memory |
|
8 |
Andersen;
Hippocampus Book |
655 |
|
Integrity at the Hippocampus Is
Required for Many Non-Spatial Learning Tasks |
|
5 |
Andersen;
Hippocampus Book |
662 |
|
A significant feature of memory
is the ability to recall facts and events and circumstances different from
those in which the information was acquired in the first place. |
|
7 |
Andersen;
Hippocampus Book |
662 |
|
Relational Processing Theory |
|
0 |
Andersen;
Hippocampus Book |
662 |
|
Declarative Memory generally involves processing the relations
between different items. |
|
0 |
Andersen;
Hippocampus Book |
662 |
|
Relational processing at encoding enables flexible access to information and situations quite different from those of the original learning. |
|
0 |
Andersen;
Hippocampus Book |
662 |
|
Relational processing is carried
out by the old capital formation, but storage at individual items in
immediate memory takes place in a perrirhinal and parahippocampal cortex. |
|
0 |
Andersen;
Hippocampus Book |
662 |
|
The role of the hippocampus in
memory is temporary, as in the declarative memory theory. |
|
0 |
Andersen;
Hippocampus Book |
663 |
|
Relational Processing Theory --
Processes and Anatomical Mediation (diagram) |
|
1 |
Andersen;
Hippocampus Book |
663 |
|
Three functional component of
the relational processing memory system |
|
0 |
Andersen;
Hippocampus Book |
663 |
|
(1) Cortical areas store
short-term memory and long-term memory traces of specific items. |
|
0 |
Andersen;
Hippocampus Book |
663 |
|
(2) The parahippocampal regions
serves as an intermediate memory for specific items and does the job of cue
compression. |
|
0 |
Andersen;
Hippocampus Book |
663 |
|
(3) The hippocampal formation
computes relational representations in a manner that enables representational
flexibility. |
|
0 |
Andersen;
Hippocampus Book |
672 |
|
Patient HM was unable to report whether he was hungry. |
|
9 |
Andersen;
Hippocampus Book |
672 |
|
Patient HM did not
ask for meals
and, quite soon after eating, attempted to eat again if a plate of food was placed before him. |
|
0 |
Andersen;
Hippocampus Book |
677 |
|
Concept of episodic
memory was first
introduced by Tulving (1972)
and elaborated in a number of ways. |
|
5 |
Andersen;
Hippocampus Book |
677 |
|
Episodic memory refers to the memory of a unique event and/or a temporary sequence of
events that collectively
comprise an episode. |
|
0 |
Andersen;
Hippocampus Book |
677 |
|
Hippocampus -- Episodic and
Episodic-like Memory |
|
0 |
Andersen;
Hippocampus Book |
677 |
|
Episodic memory is the recall,
by humans, of discrete events that happened any particular place in a
particular time. Such recall in tales of mental time travel. |
|
0 |
Andersen;
Hippocampus Book |
677 |
|
Episodic-like memory in animals
is the memory of "what, where, and when" with respect to events. |
|
0 |
Andersen;
Hippocampus Book |
677 |
|
The hippocampus is one of a
network of brain structures that mediate the automatic encoding and retrieval
of attended events and the contexts in which they occur (episodic-like
memory). |
|
0 |
Andersen;
Hippocampus Book |
677 |
|
Components of the hippocampus
formation (e.g. CA1, CA3, dentate gyrus) are differentially involved in
dissociable components of episodic-like memory, such as pattern separation
and pattern completion. |
|
0 |
Andersen;
Hippocampus Book |
677 |
|
Episodic memory and
episodic-like memory are distinguishable, as only the former requires
"autonoetic" consciousness. |
|
0 |
Andersen;
Hippocampus Book |
715 |
|
Computational Models of the
Spatial and Mnemonic Functions of the Hippocampus |
|
38 |
Andersen;
Hippocampus Book |
716 |
|
Computational modeling of the
hippocampus has followed two largely independent streams over the years: one
seeking to explain a general role in associative memory and the other
focusing on its role in spatial navigation. |
|
1 |
Andersen;
Hippocampus Book |
716 |
|
Activity (firing rate) of a neuron is viewed as a monotonic function of the amount by which the net
input to the neuron exceeds some threshold value. |
|
0 |
Andersen;
Hippocampus Book |
716 |
|
Learning is
of a Hebbian nature
such that simultaneous pre- and post-connection activity leads to increased connection strength
and
is often used in explicit analogy to synaptic
processes such as long
term potentiation (LTP). |
|
0 |
Andersen;
Hippocampus Book |
716 |
|
Anatomy in
the hippocampal
region is similar in rats, primates, and humans. |
|
0 |
Andersen;
Hippocampus Book |
716 |
|
Place cells in the neural
representation of space draws mostly on experimental data collected in rats. |
|
0 |
Andersen;
Hippocampus Book |
716 |
|
The general role of the human
hippocampus in memory for personal experience. |
|
0 |
Andersen;
Hippocampus Book |
722 |
|
Attractors in Memory, Neural
Coding, and Path Integration |
|
6 |
Andersen;
Hippocampus Book |
722 |
|
A network of recurrently
connected neurons can be arranged so a finite number of discrete patterns of
activation across the neurons are stable states or "attractors." |
|
0 |
Andersen;
Hippocampus Book |
727 |
|
Phase coding of
place cell firing with the respect to the concurrent
theta rhythm of the EEG (O'Keefe) |
|
5 |
Andersen;
Hippocampus Book |
727 |
|
The theta
rhythm is a large-amplitude
oscillation of around
6 to 10 Hz of the EEG and is present
whenever the rat is moving its head through the
environment. |
|
0 |
Andersen;
Hippocampus Book |
733 |
|
Hippocampus and Associative or
Episodic Memory |
|
6 |
Andersen;
Hippocampus Book |
733 |
|
Amnesia is the major impairment
noted in humans following bilateral damage to the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
733 |
|
Because only a relatively small
number of cases of damage restricted to the hippocampus have been studied, it
is difficult to draw general conclusions regarding its role in memory. |
|
0 |
Andersen;
Hippocampus Book |
733 |
|
Hippocampus is typically result
in a ubiquitous deficit in memory for personally experienced the events that
occur after the lesion, and spared procedural and working memory. |
|
0 |
Andersen;
Hippocampus Book |
734 |
|
Events in
the outside world are
represented by patterns of activity in neocortical areas. (Marrs 1971 model) |
|
1 |
Andersen;
Hippocampus Book |
734 |
|
The role of the hippocampus is
to store representations over the short term so relevant events can be
categorized and stored for the long term in neocortex. |
|
0 |
Andersen;
Hippocampus Book |
734 |
|
The neocortical representation
of an event is mapped into a "simple representation" in the
hippocampus, with modifiable connections to and from the hippocampus storing
the mappings between the full representation in the simple representation. |
|
0 |
Andersen;
Hippocampus Book |
734 |
|
The CA3 recurrent or lateral
some modified to store the simple representation as an associative memory --
if a simple representation is incompletely activated, the "collateral
effect" results in the full representation being recovered. |
|
0 |
Andersen;
Hippocampus Book |
734 |
|
Partial activation of the
neocortical representation of an event can lead to complete activation of its
simple representation in the hippocampus, which in turn can reactivate the
entire neocortical representation. |
|
0 |
Andersen;
Hippocampus Book |
734 |
|
The capacity at the hippocampus
system should be enough to store a day's events so the process of
categorization and long-term storage in new cortex can take place during the
following night's sleep. |
|
0 |
Andersen;
Hippocampus Book |
734 |
|
Simple representations in the
hippocampus should be sparsely encoded to reduce possible interference
between representations. |
|
0 |
Andersen;
Hippocampus Book |
734 |
|
The associated properties that
the following networks and recurrent networks are based on Hebbian learning. |
|
0 |
Andersen;
Hippocampus Book |
735 |
|
Biological implementation of
associative memory in the hippocampus (diagram) |
|
1 |
Andersen;
Hippocampus Book |
736 |
|
Anatomy of the inputs to CA3
pyramidal cells, showing the approximate number of synapses onto each cell in
the rat. (Treves and Rolls) (diagram) |
|
1 |
Andersen;
Hippocampus Book |
736 |
|
Hippocampal anatomy and a
computation model of hippocampal episodic memory function. (diagram) |
|
0 |
Andersen;
Hippocampus Book |
737 |
|
Hippocampal Representation,
Context, and Novelty |
|
1 |
Andersen;
Hippocampus Book |
738 |
|
Consolidation and Cross Modal
Binding of Events in Memory |
|
1 |
Andersen;
Hippocampus Book |
738 |
|
How the hippocampus contributes to the long-term consolidation of memories. |
|
0 |
Andersen;
Hippocampus Book |
738 |
|
The day's
events are stored in
the hippocampus, and this information is used to allow a long-term categorization and storage in the neocortex. |
|
0 |
Andersen;
Hippocampus Book |
738 |
|
The hippocampus store of
unprocessed experience has a limited capacity, and the process of extracting
relevant information from this experience to expand a long-term database
requires extensive off-line processing, perhaps during sleep. |
|
0 |
Andersen;
Hippocampus Book |
738 |
|
Anatomical convergence of information from different sensory modalities at the hippocampus. |
|
0 |
Andersen;
Hippocampus Book |
738 |
|
Associations
between the elements of an event, such as its sight, sound,
and smell. Damasio has suggested that "convergent zones" must
exist where these associations could be formed. |
|
0 |
Andersen;
Hippocampus Book |
739 |
|
Hippocampal Contributions to
Various Types of Memory and Retrieval |
|
1 |
Andersen;
Hippocampus Book |
744 |
|
The ability to specify a
proposed mechanism of hippocampal function in terms of a computational model
is invaluable in many ways |
|
5 |
Andersen;
Hippocampus Book |
744 |
|
Many questions for future
research are prompted by computational models. |
|
0 |
Andersen;
Hippocampus Book |
744 |
|
Any worthwhile theory must make
potentially falsifiable predictions. |
|
0 |
Andersen;
Hippocampus Book |
744 |
|
Investigating the link between
the properties of cells interacting a complex system such as the brain to the
resulting behavior of an animal would become almost impossible without the
aid of computational models. |
|
0 |
Andersen;
Hippocampus Book |
751 |
|
Stress and the Hippocampus |
|
7 |
Andersen;
Hippocampus Book |
769 |
|
Hippocampus and Human Disease |
|
18 |
Andersen;
Hippocampus Book |
770 |
|
Temporal Lobe Epilepsy |
|
1 |
Andersen;
Hippocampus Book |
789 |
|
Alzheimer's Disease |
|
19 |
Andersen;
Hippocampus Book |
|
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