Edelman
and Mountcastle - Mindful Brain |
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Topic |
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Mountcastle;
Organizing Cerebral Function |
10 |
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The number of neurons in a vertical lines across the thickness
of the cortex, i.e. a 30
µ diameter cylinder, is remarkably constant at about 110. |
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Mountcastle;
Organizing Cerebral Function |
11 |
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All of the cells destined for the neocortex arise from the ventricular and subventricular zones of the neural tube during the gestation period. |
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1 |
Mountcastle;
Organizing Cerebral Function |
11 |
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Cells that arise
early, mainly from the ventricular zone, may move over their short migratory
trajectories of 200 to 300 µ by extension of a process and nuclear translocation. |
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Mountcastle;
Organizing Cerebral Function |
11 |
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Cells arising later must migrate over distances of up to 10 mm;
they are guided to their final positions by moving along the surfaces of radially
oriented glial cells,
which extends across the entire wall of the neural tube. |
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Mountcastle;
Organizing Cerebral Function |
11 |
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Cortical cells are arranged in radially oriented cords or columns extending across the cortex. |
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Mountcastle;
Organizing Cerebral Function |
14 |
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A cortical
area may be defined both by its (1) intrinsic
structure and as (2)
the zone of projection
of a specific thalamic nucleus. |
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3 |
Mountcastle;
Organizing Cerebral Function |
15 |
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Cytoarchitectural differences between areas of neocortex reflect differences in their patterns of extrinsic connections. |
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1 |
Mountcastle;
Organizing Cerebral Function |
15 |
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It is apparent that neocortex is everywhere functionally uniform
and that it's progressive enlargement in mammals and particularly in primates has been accomplished by replication of a basic neural module, without the appearance of a wholly
new neuron types or qualitatively
different modes of intrinsic organization. |
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Mountcastle;
Organizing Cerebral Function |
37 |
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Basic modular unit of the neocortex is a minicolumn. |
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22 |
Mountcastle;
Organizing Cerebral Function |
37 |
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Minicolumn
is a vertically oriented cord of cells formed by the migration of
neurons from the germinal
epithelium of the neural tube along the radial glial cells to their destined location in the neocortex. |
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Mountcastle;
Organizing Cerebral Function |
37 |
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Minicolumn
contains about 110 cells. This figure is almost invariant between different neocortical
areas and different
species of mammals, except for the striate cortex of primates, where
it is 260. |
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Mountcastle;
Organizing Cerebral Function |
37 |
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Minicolumn of cells forms a vertical cylinder with a diameter of about 30 µm. |
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0 |
Mountcastle;
Organizing Cerebral Function |
37 |
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Since the total
volume of the human
neocortex is about 1000
cm3, and
assuming an average thickness of 2,500 µm, neocortex of the human brain has a surface area of about 4,000 cm2 and contains about 600 million minicolumns and on the
order of 50 billion neurons. |
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Edelman; Group Selection and Reentrant Signaling |
74 |
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Role of the reticular formation for arousal indicates that there are areas of the brain outside of the cortex that necessary for consciousness. |
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37 |
Edelman; Group Selection and Reentrant Signaling |
81 |
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Minimal activation period of about 200-500 ms for awareness of a near-threshold stimulus. |
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7 |
Edelman; Group Selection and Reentrant Signaling |
81 |
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Studies end experimental
psychology suggest that a full perception requires no more than 100 ms of intracortical processing time. |
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Edelman; Group Selection and Reentrant Signaling |
81 |
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The brain functions for action. |
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Edelman; Group Selection and Reentrant Signaling |
82 |
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Central programming of motor patterns is predominant over simple reflex patterns. |
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1 |
Edelman; Group Selection and Reentrant Signaling |
82 |
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Hippocampal function in attentional states is related to the performance of
motor acts. |
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Edelman; Group Selection and Reentrant Signaling |
88 |
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Early in development, cell groups or polyclones are determined by gene expression and programming. |
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6 |
Edelman; Group Selection and Reentrant Signaling |
88 |
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Large degeneracy is built into the system. Many
more cell groups than are ultimately used to make
projections and connections. Many of the "unused"
cells die. |
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Edelman; Group Selection and Reentrant Signaling |
88 |
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A hierarchy
of interactions occurs, with early decisions (such as branching
of limb plexus neurons) being relatively few in
number and decided by
the gene program. |
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Edelman; Group Selection and Reentrant Signaling |
88 |
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Interaction between cell groups are sequential, selective, and determined by mutual influence. |
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Edelman; Group Selection and Reentrant Signaling |
88 |
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Result of selective
interaction is the loss
of synaptic connections and the death of many CNS neurons during
development. |
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Edelman; Group Selection and Reentrant Signaling |
89 |
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Enormous degeneracy and selection early in the system, even before
primary repertoire formation is complete. |
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1 |
Edelman; Group Selection and Reentrant Signaling |
89 |
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Later developments, such as those in critical
periods, may reduce
degeneracy by selective
synaptic stabilization. |
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Edelman; Group Selection and Reentrant Signaling |
89 |
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Prefrontal, frontal, and temporal cortices have a constantly extended critical period, which in fortunate individuals may be delayed until death. |
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Edelman; Group Selection and Reentrant Signaling |
90 |
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Central pattern generators and autonomous reflexes can give rise to a highly adaptive and complex forms of behavior. [Stereotyped motor
programs] [FAPs] |
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Edelman; Group Selection and Reentrant Signaling |
92 |
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Groups of cells, not single cells, are the main unit of selection in higher brain functions. |
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2 |
Edelman; Group Selection and Reentrant Signaling |
92 |
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Groups of cells in higher brain functions will be found to be multiply
represented, degenerate, and isofunctionally overlapping. |
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Edelman; Group Selection and Reentrant Signaling |
93 |
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Although single neurons may
occasionally function as a group, no pontifical neuron or single-neuron "decision
unit" will ever be found at the highest level of a system of any
large degree of plasticity. |
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1 |
Edelman; Group Selection and Reentrant Signaling |
93 |
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Correlations
will be found that suggest phase reentrant signaling on degenerate neuronal groups with periods of 50-200 ms. |
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Edelman; Group Selection and Reentrant Signaling |
93 |
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The most
likely correlations will be found between cortical, thalamocortical, and limbic-reticular signals. |
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Edelman; Group Selection and Reentrant Signaling |
94 |
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Properties of the central
nervous system -- (1) distributed nature of
learning, (2) associative nature of recall, (3) adaptive reaction to novelty,
capacity to make (4) highly abstract
representations in a world
model. |
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Edelman; Group Selection and Reentrant Signaling |
94 |
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Structured neuronal groups containing up to 10,000 neurons are formed during embryogenesis and development. Intrinsic connections within a group and extrinsic connections among groups are specified by gene programming and synaptic selection. |
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Edelman; Group Selection and Reentrant Signaling |
94 |
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Consciousness
includes the ability to accumulate memories and to recall them associatively in temporal sequences. |
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Edelman; Group Selection and Reentrant Signaling |
94 |
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Consciousness
includes the capacity to distinguish self from nonself (self-awareness). |
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Edelman; Group Selection and Reentrant Signaling |
95 |
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The conscious
state results from phasic
reentrant signaling occurring in parallel
processes that involve associations between stored patterns and current sensory or internal input. |
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1 |
Edelman; Group Selection and Reentrant Signaling |
95 |
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Awareness
is assumed to arise as a result of the
access by groups of higher order neurons to rich multimodal associative
patterns stored in long-term
memory as a result of past experience. |
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Edelman; Group Selection and Reentrant Signaling |
95 |
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Sequential tagging of stored events allows for recall in a proper time scale and order. |
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Edelman; Group Selection and Reentrant Signaling |
95 |
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Because of the selective,
group-degenerate, and phasic nature of reentrant cycles and the capacity of higher-order
neurons to abstract
sequences of events, a continuous
shifting pattern of associations can be
made. [Fuster's perception-action cycle] |
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Edelman; Group Selection and Reentrant Signaling |
95 |
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Consciousness
is considered to be a form of associative
recollection with updating, based on present reentrant input, that continually confirms or
alters a "world
model" or "self" by means of parallel motor or sensory outputs.
[recursion] [Bayesian inference] [Fuster's
perception-action cycle] |
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Edelman; Group Selection and Reentrant Signaling |
95 |
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Brain's entire neurological
process depends upon the properties of group selection and reentrant signaling in a nervous system that is already specified by
embryological, developmental, and evolutionary events. |
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Edelman; Group Selection and Reentrant Signaling |
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