Rolls;
Memory, Attention, and Decision-Making |
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Rolls; Memory, Attention, and Decision-Making |
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To gain an understanding of neural processes and consciousness it is helpful to simulate the brain's processing on a computer, and to show whether the simulation can perform the task of memory systems in the brain, and whether the simulation has similar properties to the real brain. |
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Rolls; Memory, Attention, and Decision-Making |
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Attention
and decision-making
can be understood in terms of interactions between the fundamental operations in memory systems in the brain. |
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Empirical evidence to validate
the understanding of neural
processes and consciousness is largely from nonhuman primates and from humans, because of the considerable similarity of their memory and related systems. |
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Many of the processes involved
in memory, perception, attention, and decision-making in the brain can be understood in terms of the operation of
different types of memory networks and the interactions between these networks. |
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To understand memory,
perception, attention, and decision-making in the brain, we
are dealing with large-scale
computational systems with interactions between the parts. |
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Understanding cognitive functions such as object recognition, memory recall, attention, and decision-making requires single neuron data to be closely linked to the computational models of how the interactions between large numbers of neurons in many networks of neurons allow these cognitive problems to be solved. |
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Information
is exchanged by the spiking activity between the neurons of the brain. |
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It is important to analyze the
activity of single neurons and populations of neurons in order to understand brain
function. |
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Understanding
how neurons represent information is
fundamental for understanding how neurons and networks of neurons read the code from other neurons, and the actual
nature of the computation that could be performed in a memory
network. |
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Neurocomputational models enable the single neuron level of analysis to be linked to the level of large-scale
neuronal networks and the interactions between them, so that large-scale processes such as memory retrieval, object recognition, attention, and decision-making can be understood. |
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Long-term potentiation and long
term depression as models of synaptic modification. |
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Schematic illustration of synaptic modification rules as
revealed by long-term potentiation (LTP) and long term depression (LTD). (diagram) |
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In that LTP is long-lasting, develops rapidly, is synapse specific, and is in some cases associative, it is of interest as a potential synaptic
mechanism underlying some
forms of memory. |
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A sparse
distributed representation is a distributed
representation in which a small portion of the
neurons is active at
any one time. |
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One advantage of distributed encoding is that the similarity between two
representations can be reflected by the correlation between the two patterns of activity that represent the different
stimuli. |
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Another advantage a distributed encoding is that the number of different stimuli that can be represented can be very large. |
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Pathways
involved in some different memory systems (diagram) |
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Fine Structure and Connectivity
of the Neocortex |
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The neocortex consists of many areas that can be distinguished by the appearance of the cells (cytoarchitecture) and fibers or axons
(myeloarchitecture), but nevertheless, the basic organization of the different neocortical areas has many similarities. |
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Excitatory Cells and Connections |
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The main
information bearing afferents to a cortical area have many terminals in layer 4. |
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Primary sensory cortical areas received their inputs from the primary sensory thalamic
nucleus associated with the specific sensory modality. |
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Spiny stellate cells are so-called because they have radially
arranged, star-like
dendrites. |
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Spiny stellate cell axons usually terminate within the
cortical area in which they are located. |
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Each thalami axon makes 1000 -- 10,000 synapses, not more than several (or at
most 10) of which are onto
any one spiny stellate cell. |
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In non-primary
sensory areas, important information bearing afferents from a preceding cortical area terminate
in layer 4, but they
are no or few spiny stellate cells in this layer. |
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Layer 4 still
looks granular (due
to the presence of many small cells), but these cells are typically small
pyramidal cells. |
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Spiny stellate cells and small pyramidal cells are similar in many ways. |
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The axons of the superficial (layer 2 and 3) pyramidal cells have collaterals and terminals in layer 5. |
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The axons of the superficial (layer 2 and 3) pyramidal cells axons
also typically project
out of that cortical area, and onto the next cortical area in sequence,
where they terminate in layer 4, forming the forward
cortico-cortical projection. |
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It is also from the superficial layer 2 and 3 pyramidal cells that projections to the amygdala arise in some sensory areas that are high in the hierarchy. |
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Axons of layer
5 pyramidal cells have many
collaterals in layer 6. Axons of these layer 6
cells typically leave the cortex to project to subcortical sites (such as the striatum), or back to the preceding cortical area to terminate in layer 1. |
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There are as many of these back projections as there are forward connections between two sequential cortical areas. |
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Layer 6 pyramidal cells have prolific dendritic
arborizations in layer
4 and receive synapses from thalami afferents and also from pyramidal cells in other cortical layers. |
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Layer 6 pyramidal cells form backprojections to the thalmic
nucleus from which it receives
projections, . |
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Axons of layer
6 cells also contribute to the backprojections to layer 1 of the preceding cortical area. |
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Although the pyramidal and spiny stellate cells form the great majority of neocortical neurons with excitatory outputs, there are in
addition several further cell types. |
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Bipolar cells
are found in layers 3 and 5, and are characterized by having two dendritic
systems, one ascending and the other descending, which together with the axon
distribution, are confined to a narrow vertical column often less than 50 µ
in diameter. |
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Inhibitory Cells and Connections |
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There are a number of types of
neocortical inhibitory neurons,
all having no spines
and using GABA as a neurotransmitter. |
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A number of types of inhibitory neurons can be distinguished, best by their axonal distributions. |
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One type of inhibitory neuron,
the basket cell, present in
layers 3--6, has few spines on his dendrites so that it can be described as smooth, and has an axon that
participates in the formation of weaves of preterminal axons which surround
the cell bodies of pyramidal cells, and form synapses directly on the cell
body, but also onto the dendritic spines. |
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Basket cells
comprise 5 -- 7% of the total cortical cell population, compared with
approximately 72% for pyramidal cells. |
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Basket cells
receive synapses from the main extrinsic
afferents to the neocortex, including thalami
afferents, so they must contribute to a feedforward type of inhibition of pyramidal cells. |
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They feedforward mechanism of basket cells allows the pyramidal cells to be set
to an appropriate sensitivity for the input they are about to receive. |
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The neurotransmitter
used by the basket cells is GABA. |
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Dendrites
of basket cells can extend laterally 0.5 mm or more
(primarily within the layer at which the cell body is located), and the axons can also extend laterally from the cell
body 0.5 -- 1.5 mm. |
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The basket cells produce a form of lateral inhibition that is quite spatially extensive. |
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Each basket
cell may make 4--5
synapses with a given pyramidal
cell;
each pyramidal cell may receive from 10--30 basket cells; and each basket cell may inhibit approximately 300 pyramidal cells. |
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The number of synapses per neuron may be 40,000 for humans. |
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The great majority of cortical excitatory synapses are
made from axons of cortical pyramidal cells. |
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Micro-anatomical studies show
that pyramidal cells rarely
make more than one connection with any
other pyramidal cell,
even when they are adjacent in the same area of the cerebral cortex. |
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The probability that a pyramidal cell makes a synapse with its neighbor is low, approximately 0.1. |
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Within a cortical
area of perhaps 1 mm˛, the region within which typical pyramidal
cells have dendritic
trees and their local
axonal arborization, there is a probability of excitatory-to-excitatory cell connection of 0.1. |
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The local
population of mutually interconnected pyramidal neurons is served by its
own population of inhibitory neurons, which have a spatial receiving and sending zone
and the order of 1 mm2. |
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The architecture of local pyramidal neurons and inhibitory neurons is the
effectively recurrent
or reentrant. It may
be expected to show some of the properties of recurrent
networks, including fast
dynamics. |
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The fast dynamics of local recurrent networks may be
facilitated by the fact that cortical neurons in the awake state have a low spontaneous
rate of firing (a few Hz), which means that any small
additional input may produce
some spikes sooner than otherwise would have
occurred, because some of the neurons may be very close to a threshold
of firing. |
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Typical quantitative estimates
or neocortex (table) |
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Local recurrent networks might also show some of the autoassociative
retrieval of information typical of autoassociation networks, if the synapses between the nearby
pyramidal cells have the appropriate Hebbian modifiability. |
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The connection
probability between hippocampal
CA3 pyramidal cells is approximately 0.02--0.04, and this is thought to
be sufficient to sustain associative retrieval. |
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In the neocortex, each 1 mm2 region within which there is a relatively high density of recurrent collateral connections
between pyramidal cells
probably overlaps
somewhat continuously with the next. |
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The anatomy of local connections between nearby pyramidal cells and local inhibitory neurons may provide a
network basis for understanding the columnar
architecture of the neocortex, for it implies
that local recurrent
connectivity on this scale is a feature of the
cortical computation. |
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Functional Pathways through
Cortical Layers |
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Basic circuit for visual cortex (diagram) |
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The forward
corticocortical afferents to a cortical area
sometimes have a columnar pattern it to their distribution with the column
width 200-300 µ in
diameter. |
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Individual thalamocortical
axons often end in patches in layer 4 which are 200-300 µ in diameter. |
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The dendrites of spiny stellate cells are in the region of 500 µ in diameter, and
their axons can distribute in patches 200-300 µ
across, separated by distances up to 1 mm. |
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Dendrites
of layer 2 and 3
pyramidal cells can
be approximately 300 µ in diameter. |
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In the hierarchy of cortical stages, convergence and competition are key aspects of the processing. |
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The hierarchy
of cortical processing could act in a feedforward manner since it it has
been shown there is insufficient time for top-down processing to occur when objects can just be recognized. |
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Neurons in each cortical stage respond for 20-30 ms when an object can just be seen. |
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Given that the
time for processing to travel from V1 to inferior
temporal visual cortex (IT) is approximately 50 ms, there is insufficient time for a return projection from IT to reach V1, influence the
processing there, and in turn for V1 to project up to IT to alter the processing there. |
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Backprojections are a major feature of cortical connectivity. |
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Learning --
the way in which the back projections could assist learning in the cortex. |
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Recall |
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During recall, neural activity occurs in the cortical areas involved in the original processing. |
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Semantic Priming |
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Backprojection architecture could implement semantic priming by using the backprojecting neurons to provide a small activation of just those neurons that are appropriate for
responding to the semantic
category of input
stimulus. |
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Attention
can operate from higher to lower levels, to selectively facilitate only certain pyramidal cells by using the backprojections. |
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If the forward
connections from one
cortical area to the next, and the return backprojections, are both associatively modifiable, then the coupled networks could be regarded as, effectively, an autoassociative network. |
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Hippocampus and Memory |
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A theory of
the hippocampus in
which the CA3 neurons
operate as an autoassociation memory to store episodic memories including object and place memories, and the dentate granule cells operate as a preprocessing stage by performing pattern separation so that the mossy fibers could act to set up different
representations for each
memory to be stored in
the CA3 cells. |
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Diluted connectivity of the recurrent collateral
connections found in real biological networks. |
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The primate
hippocampus receives major
inputs via the entorhinal
cortex (area 28). |
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The hippocampus is by its connections potentially able to associate together object representations (from the temporal
lobe visual and auditory areas) and spatial representations. |
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The entorhinal
cortex receives inputs from the amygdala and the orbitofrontal cortex, which could provide reward related information to the hippocampus. |
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The final
convergence afforded by the hippocampus into one network in CA3 may be especially appropriate
for episodic memory typically involving arbitrary
associations between the any of the inputs of the hippocampus,
e.g. spatial, vestibular related to self motion,
visual object, olfactory, and auditory. |
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There are also directs subcortical inputs to the hippocampus from the amygdala and septum. |
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The primary output from the hippocampus to neocortex originates in CA1 and projects to subiculum, entorhinal cortex, and parahippocampal structures as well
as prefrontal cortex. |
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CA1 and subiculum also project via the fornix to subcortical areas such as the mammillary bodies and anterior thalamic nuclei. |
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Damage to fornix
connections to the hippocampus produced deficits in learning about the places of objects and about the places where responses should be made. |
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Spatial processing involves a snapshot type of memory, in which one whole scene must be remembered. This memory may then be a special case of episodic memory, which involves an arbitrary
association of a particular
set of events that describe a past episode. |
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It is suggested that an autoassociation memory implemented
by the CA3 neurons
enables whole (spatial) scene or episodic memories to be formed, with a snapshot
quality that depends on the arbitrary associations that can be
made in the short temporal window that characterizes the synaptic
modifiability in this system. |
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The hypothesis is that the autoassociation memory enables arbitrary sets of concurrent neuronal firings, representing for example the spatial
context where the episode occurred, the people present during the episode,
and what was seen during
the episode, to be associated together and stored as one event. |
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Later recall
of the episode from
the hippocampus in
response to a partial cue can then lead to reinstatement of
the activity in the neocortex that was originally present during
the episode. |
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The
autoassociation memory described here shows how
the episodic memory
could be stored in the hippocampus, and later retrieved from the hippocampus and thereby to the neocortex using backprojections. |
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Experimental data show that recognition memory is not impaired by hippocampal damage. |
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Spatial representation in the hippocampus of rats
is about the place where the rat is, whereas the spatial
representation in primates includes a representation of space
"out there", as represented by spatial view cells. |
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A theory of the operation of hippocampal
circuitry as the memory
system. |
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Hippocampal circuitry |
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CA3 as an Autoassociation Memory |
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Representation of connections within the hippocampus (diagram) |
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Architecture of an Attractor or Autoassociation neural
network. (diagram) |
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A fundamental property of the autoassociation model of the CA3 recurrent collateral network is
that it can implement a short-term memory by maintaining
the firing of neurons using the excitatory recurrent collateral connections. |
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A stable attractor can maintain one memory active for a considerable period, until a new input pushes the attractor to represent a new location or memory. |
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An attractor
network is one in which a stable pattern of firing is maintained once it has been started. |
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Dynamics of
the recurrent network. |
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How quickly
does a recurrent network settle into its final
state? |
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How long
does it take the for a pattern of activity,
originally evoked in CA3 by afferent inputs, become influenced by the activation of recurrent collaterals? |
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Memory for Sequences |
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Theta oscillations (5-8 Hz) and Gamma oscillations (30-80 Hz) |
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Almost Poisson nature of the spike trains of single neurons found in most brain areas. |
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Mossy Fiber Inputs to CA3 cells |
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Mossy fibers
may be necessary for new learning in the hippocampus, but may not be necessary for recall of existing
memories from the hippocampus |
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Perforant path inputs to CA3 cells |
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Dynamics of
the network is dominated
by the randomizing effect of the recurrent collaterals. |
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Associatively modifiable
synapses are needed in the same order as the number of concurrently stored patterns, so that small cues can be effective. |
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The perforant
path system is the one involved in relaying the cues that initiate
retrieval. |
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The three
major classes of excitatory
input to the CA3 cells
(recurrent collateral, mossy fiber, and perforant path) could be independently scaled by virtue of
the different classes
of inhibitory interneurons. |
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Dentate granule cells |
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The dentate
granule cell stage of hippocampal
processing, which precedes
the CA3 stage, acts to produce
during learning the sparse
yet efficient representation in CA3 neurons that is required for
the autoassociation to
perform well. |
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The learning of spatial view and place cell representations from visual inputs. |
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Linking the
inferior temporal visual cortex to spatial view and place cell representations. |
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CA1 cells |
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Backprojections to the neocortex |
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Backprojections to the neocortex
-- quantitative aspects |
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CA3 subregion of the hippocampus |
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The types of information
associated in CA3 |
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Pattern Completion in CA3 |
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Recall In CA3 |
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|
Mossy fiber vs
direct perforant path input to CA3 |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
99 |
|
Orthogonal representations in CA3 |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
100 |
|
Short-term memory, path integration, and CA3 |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
101 |
|
CA1 subregion of the hippocampus |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
101 |
|
Sequence Memory and CA1 |
|
0 |
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102 |
|
Associations across time, and CA1 |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
103 |
|
Order memory,
and CA1 |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
104 |
|
Intermediate memory, and CA1 |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
105 |
|
Evaluation of the theory of hippocampal function |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
109 |
|
Comparison
of other theories of hippocampal function |
|
4 |
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113 |
|
Reward- and
Punishment-related Learning -- Emotion and Motivation |
|
4 |
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113 |
|
Emotions
can be considered as states elicited by reinforcing
stimuli, i.e. by rewards and punishers. |
|
0 |
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113 |
|
We need to understand which stimuli are primary, i.e. unlearned, reinforcers; and we
need to understand the associative processes that enable other previously
neutral stimuli to come associated with these primary reinforcers. |
|
0 |
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114 |
|
Primary Reinforces (table) |
|
1 |
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116 |
|
Associative processes involved in reward and punishment related learning. |
|
2 |
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116 |
|
Pavlovian
or Classical Conditioning |
|
0 |
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116 |
|
Stimulus-Response Association |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
118 |
|
Conditioned Stimulus (CS) --
Unconditioned Stimulus (US) Associations |
|
2 |
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119 |
|
Hedonic assessment |
|
1 |
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120 |
|
Overtraining in an instrumental
task results in instrumental behavior that becomes performed as a fixed
inflexible habit. |
|
1 |
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120 |
|
Stimulus -- Response Habits |
|
0 |
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121 |
|
The main brain regions
implicated in reward and punishment related learning include the amygdala,
orbitofrontal cortex, cingulate cortex, and basal forebrain areas including the
hypothalamus. |
|
1 |
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122 |
|
Pathways
involved in emotion
(diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
123 |
|
Connections
of the taste, olfactory, somatosensory, and visual pathways in the brain (diagram) |
|
1 |
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124 |
|
Representations of primary reinforcers. |
|
1 |
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125 |
|
Taste |
|
1 |
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125 |
|
Smell |
|
0 |
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126 |
|
Pleasant
and painful touch |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
128 |
|
Visual stimuli |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
128 |
|
Although most of visual stimuli are not primary reinforcers, but may
become secondary reinforcers as a result of stimulus-reinforcer
autoassociation learning, it is possible that some visual stimuli, such as the
sight of a smiling face
or of an angry face,
could be primary reinforcers. |
|
0 |
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128 |
|
For humans, the reinforcing value of face expression could be the decoded by the cortical processing of the
inferior temporal visual cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
128 |
|
The inferior
temporal visual cortex also projects into the amygdala, in which face-selective neurons are also
found. |
|
0 |
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128 |
|
A population of face-selective neurons is also
found in the orbitofrontal cortex. |
|
0 |
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129 |
|
Orbitofrontal
and cingulate cortex
lesions can impair humans' ability to identify
the emotional expression
on a face. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
129 |
|
Some of the
face-selective neurons in the amygdala and orbitofrontal cortex reflect the secondary reinforcing value of the face, given the role these brain
regions play in stimulus-reinforcer association
learning. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
129 |
|
In humans, it is then found that activation of the orbitofrontal cortex is correlated with the attractiveness
of the face. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
129 |
|
It is possible that some auditory stimuli can be primary reinforcers. Where the reinforcement may be decoded is not yet known, though auditory
neurons that respond
to vocalization have
been found in orbitofrontal cortex and amygdala, and may also be present in the cingulate
cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
129 |
|
Orbitofrontal
and cingulate cortex lesions can impair humans ability to identify the emotional expression in a voice. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
129 |
|
Novel stimuli
are somewhat rewarding and in this sense act as primary
reinforcers. The value of this type of reinforcer
is that it encourages animals to explore new
environments in which their genes might produce a fitness advantage. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
129 |
|
Neurons that respond to visual stimuli that are associated
with rewards, and to novel stimuli, have been
discovered in the primate amygdala, and this evidence suggests that the neurons are involved in
the primary reinforcing
properties of novel stimuli. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
129 |
|
Representing potential secondary reinforcers. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
131 |
|
Generalization -- if we learn an emotional response to an object, we usually want to
generalize the emotional response to other similar objects. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
132 |
|
Graceful degradation |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
133 |
|
Objects,
and not their reward and punishment associations, are represented in the inferior temporal visual
cortex. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
135 |
|
Why reward
and punishment associations of stimuli are not represented early in the information processing in the primate brain. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
136 |
|
Orbitofrontal Cortex |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
136 |
|
Phineas Gage |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
137 |
|
Prefrontal leucotomy |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
140 |
|
Effects of damage to the orbitofrontal cortex. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
142 |
|
Orbitofrontal cortex contains a major cortical
representation of taste. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
147 |
|
An olfactory
representation in the orbitofrontal
cortex. |
|
5 |
Rolls; Memory, Attention, and Decision-Making |
151 |
|
Flavor representation -- convergence of taste and olfactory inputs in
the orbitofrontal cortex. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
153 |
|
Visual inputs
to the orbitofrontal cortex. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
153 |
|
Visual stimulus-reinforcer
association learning and reversal. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
153 |
|
There is a major
visual input to many neurons in the orbitofrontal cortex, and what is
represented by these neurons in many cases is the reinforcer
(reward all punisher) association of visual stimuli. The primary
reinforcer that has been used is taste. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
153 |
|
The orbitofrontal
cortex visual neurons in many cases reverse their responses to visual stimuli when the taste with which the visual stimuli stimulus is associated
is reversed. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
164 |
|
A representation
of faces in the orbitofrontal cortex. |
|
11 |
Rolls; Memory, Attention, and Decision-Making |
164 |
|
There is a population of orbitofrontal cortex face-selective neurons that respond in many ways similar to those in the temporal cortical
visual areas. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
165 |
|
Orbitofrontal face responsive
neurons tend to respond with
longer latencies (130-220
ms typically) than temporal
lobe neurons (80-100
ms). They also convey information about which face is being seen, by having
different responses to
different faces. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
165 |
|
Some of the face
identity neurons in similar
responses to different
views of a face, which is a useful property of
neurons responding to face identity. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
165 |
|
Some face
neurons respond to moving but not still heads. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
165 |
|
Some face
neurons are tuned to face
expression. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
165 |
|
Neurons with face
expression, face movement, or face view-dependent responses would
all be useful as part of a system decoding and representing signals important in social interactions. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
The representation of face identity is also important and
social interactions,
for it provides some of the information needed in order to make different responses to different individuals. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
Some orbitofrontal
cortex neurons were shown to be tuned to auditory stimuli, including for some neurons the sound of vocalizations. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
Activation of the lateral orbitofrontal cortex
occurs when a rewarding smile expression is expected, but an angry face expression is obtained, a visual discrimination reversal. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
Activation
of the orbitofrontal cortex is found when humans are making social
judgments. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
Auditory stimuli may have similar representations in the orbitofrontal cortex related to their affective value. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
Researchers have found a correlation between subjective ratings of dissonance and consonance of musical chords in the activations
produced in the orbitofrontal cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
Affective states, moods, can influence cognitive
processing, including perception and memory. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
166 |
|
Cognitive processing events, if decoded as being rewarding or punishing, can produce emotional states. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
175 |
|
Human orbitofrontal
cortex. |
|
9 |
Rolls; Memory, Attention, and Decision-Making |
183 |
|
Orbitofrontal cortex has a key role in representing
primary reinforcers, and learning and rapidly changing associations
between stimuli and primary reinforcers, and thus is
important in many types of emotional and motivational behavior. |
|
8 |
Rolls; Memory, Attention, and Decision-Making |
183 |
|
Individual differences in the functioning of the orbitofrontal cortex may contribute to differences in
personality, the psychiatric
states, and to differences
in the rewards that drive
people to action. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
187 |
|
Amygdala |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
188 |
|
Connections
to the amygdala. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
189 |
|
Connections
to the amygdala,
monkey brain (diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
190 |
|
Effects of amygdala
lesions. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
196 |
|
Neuronal activity in the primate amygdala that the reinforcing stimuli. |
|
6 |
Rolls; Memory, Attention, and Decision-Making |
201 |
|
LeDoux has
described a theory of the neural basis of emotion which is conceptually similar to that of Rolls, except that
he focuses mostly on the role of the amygdala in emotion (and not on other brain regions such is the orbitofrontal cortex); except that
he focuses mainly on fear; and except that he suggests from neurophysiological findings
that an important route for conditioned emotional
stimuli to influence
behavior is via the
subcortical inputs (especially from the medial
part of the medial geneticulate nucleus of the thalamus) to the amygdala. |
|
5 |
Rolls; Memory, Attention, and Decision-Making |
201 |
|
Humans and
other animals do not generally want to learn that a particular pure tone is associated with the reward or punishment. Instead, it might be
that a particular complex pattern of sounds such as a vocalization carries a reinforcement signal, and this may be independent of the exact pitch at which it is uttered. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
202 |
|
Responses
of these amygdala neurons to reinforcing and novel stimuli. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
204 |
|
Neuronal responses in the amygdala to faces. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
211 |
|
Cingulate Cortex |
|
7 |
Rolls; Memory, Attention, and Decision-Making |
212 |
|
Anterior or
perigenual cingulate cortex, reward, and affect. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
216 |
|
A current working hypothesis is
that the affective part of
the anterior cingulate cortex receives inputs about expected rewards and
punishers, and about the rewards and punishers received, from the orbitofrontal cortex and amygdala. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
216 |
|
The anterior
cingulate cortex may act as an output system for emotional responses and actions. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
217 |
|
Mid-cingulate cortex, the cingulate motor area, and action-outcome learning. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
217 |
|
The
mid-cingulate area may be divided into an anterior or rostral cingulate motor area concerned with skeletomotor
control which may be required in avoidance and fear, and a posterior or caudal cingulate motor area which may be more involved in skeletomotor
orientation. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
218 |
|
Brain mechanisms of action-outcome learning may involve the anterior
cingulate cortex. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
218 |
|
Reward and punisher-related
information may reach the mid-cingulate
area, where it can be associated with skeletomotor response representations. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
218 |
|
It is useful to place action-outcome learning and a wider
context of emotion. When stimuli are presented, they are decoded to determine whether they are primary
rewards or punishers by structures such as the orbitofrontal
cortex and amygdala. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
218 |
|
When reinforcer
contingencies change, the orbitofrontal cortex is important
in reversing the stimulus-stimulus association, and contains appropriate
error neurons. The orbitofrontal cortex is involved in this way in decision-making and executive function. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
219 |
|
Human brain
imaging investigations of mood and depression. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
220 |
|
Output pathways for reward- and
punisher-guided behavior, including emotional responses. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
220 |
|
Autonomic and endocrine systems |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
221 |
|
Motor systems
for implicit responses,
including the basal ganglia, reinforcement learning, and dopamine. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
221 |
|
Systems-level architecture of
the basal ganglia. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
224 |
|
System-level analysis of the basal ganglia -- neuronal activity in different
parts of the striatum. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
225 |
|
Ventral Striatum |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
230 |
|
Tail of the caudate
nucleus, and posteroventral putamen. |
|
5 |
Rolls; Memory, Attention, and Decision-Making |
231 |
|
Postero-ventral putamen |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
232 |
|
Head of the caudate
nucleus |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
237 |
|
Computations
performed by the basal ganglia. |
|
5 |
Rolls; Memory, Attention, and Decision-Making |
243 |
|
Dopamine,
reinforcement, and reinforcement
learning. |
|
6 |
Rolls; Memory, Attention, and Decision-Making |
245 |
|
Dopamine neurons could not convey information about a primary reward obtained if the trial is successful, in the way that orbitofrontal cortex neurons do. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
249 |
|
Basal forebrain and hypothalamus |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
249 |
|
Basal forebrain cholinergic neurons |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
251 |
|
Noradrenergic neurons |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
252 |
|
Opiate reward systems, analgesia, and food reward. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
253 |
|
Effects of emotion on cognitive processing and memory. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
254 |
|
Backprojections from the primate amygdala to the cortex spread more widely than the afferent connections, which for vision come mainly from the inferior temporal visual cortical areas. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
255 |
|
Pyramidal cells in layers 2 and 3 of the temporal lobe association
cortex receive forward
inputs from preceding
cortical stages of processing, and also backprojections from the amygdala and orbitofrontal cortex. (diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
255 |
|
Theory of how the effects of mood on memory and perception could be implemented in the brain. Massive backprojections from parts of the brain where mood
is represented, such it the orbitofrontal cortex and amygdala, to the cortical areas
such as the inferior temporal visual cortex and hippocampus-related areas that project into these mood-representing areas. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
255 |
|
The computer
model of the effects of mood on memory and perception uses an attractor network in the mood module, which helps the mood to be an enduring state, and also an attractor in the inferior temporal visual
cortex (IT). |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
255 |
|
The computer
model of mood the system is treated as a system of couple attractors with many different perceptual states
associated with any one moods state. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
255 |
|
Overall, there is a large number of perceptual/memory states, and only a few moods states, so that
there is a many-to-one relation between perceptual/memory states and the associated moods states. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
255 |
|
The mood
computer model reveals the ability of a perceptual input to trigger a mood
state in the amygdala if there is not an existing mood, but greater difficulty to induce
a new mood if there is already
a strong mood attractor present. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
256 |
|
General effects needed for forward and backward projections in the brain -- forward
projections must be relatively
strong to produce new
firing in a module when a new (forward) input is
received, and backward projections must be relatively weak, if they are to mildly implement top-down
constraints without dominating
the activity of the earlier
modules. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
Laterality effects in human reward and emotional processing. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
Damage to the left
hemisphere (in right-handed
people) is more likely to affect language, and to the right hemisphere is more likely to
affect emotional processing. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
Greater probability of impairments in recognizing facial expressions
after right rather
than left hemisphere damage. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
Patients are more likely to be depressed by a stroke if it is to the left than to the right hemisphere. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
The result for strokes may
indicate that to feel depressed, the right hemisphere is normally involved. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
Experience with split-brain patients provides
evidence that processing of implicit information about emotion can be dissociated from explicit, language-based systems. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
Face identification deficits are not necessarily associated with face expression identification
impairments. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
257 |
|
Why should there be some lateralization of emotional processing in
humans? One argument is that whenever
a function does not need to be represented
bilaterally due to the topology of the body, then it is more
efficient to place the group
of neurons concerned with that processing close together. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
258 |
|
An advantage of genetic specification of connectivity between neuron types,
and of keeping neurons concerned with the same computation close
together, is that this minimizes
the problem of guidance
of axons toward their targets. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
258 |
|
Some distant
parts of the brain that are connected in adults are connected
because the connections can be made early in
development, before the different brain regions
have migrated to become
distant. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
258 |
|
Wherever possible, neurons performing the same computation should be close together. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
258 |
|
Where there is no body-symmetry reason to have separate representations for each side of the body, the representation would optimally be lateralized. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
262 |
|
Invariant visual object
recognition learning. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
262 |
|
Invariant representations of faces
and objects in the inferior temporal visual cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
263 |
|
Schematic diagram of the visual pathways from the retina to
the visual cortical areas (diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
263 |
|
Processing to the inferior temporal cortex in the
primate visual system. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
264 |
|
Translation invariance and receptive field size. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
268 |
|
Size and spatial frequency
invariance. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
269 |
|
Combination of features in the correct spatial configuration. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
270 |
|
A view-invariant representation. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
274 |
|
Learning of
new representations in
the temporal cortical visual areas. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
275 |
|
Rapid learning of representations of new objects appears to be a major type of
learning in which the temporal
cortical areas are involved. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
276 |
|
Distributed encoding |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
277 |
|
Responses
of a face-selective neuron in the inferior temporal visual
cortex to four
different faces (diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
281 |
|
Face expression, gesture and view
represented in a population of neurons in the cortex in the inferior
temporal sulcus. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
281 |
|
Specialized regions in the temporal cortical visual
areas. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
283 |
|
Neuroimaging data provides evidence consistent with neurophysiology that they are different face
processing systems in the human brain, and different processing subsystems for
objects, moving objects,
and scenes. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
284 |
|
The amygdala and orbitofrontal cortex may become activated particularly by certain face expressions. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
284 |
|
Different inferior temporal
cortex neurons respond differently to different categories of visual stimuli, some neurons conveying information primarily about faces, and others about objects. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
284 |
|
In the inferior
temporal cortex, there are small clustered groups of neurons,
with neurons within a cluster responding to somewhat similar
attributes of stimuli, and different clusters responding to different categories or types of
visual stimuli. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
299 |
|
VisNet is a
model of invariant object recognition based
on Edmund Rolls's
hypothesis. It is a computer simulation that allows hypotheses to be tested and developed about how multilayer hierarchical networks of
a type believed to be implemented in the visual
cortex pathways operate. |
|
15 |
Rolls; Memory, Attention, and Decision-Making |
299 |
|
The VisNet
model, as with all models, requires precise specification for what is to be implemented, and it
is same time involves specified simplifications of the real
architecture, as investigations of the fundamental
aspects of the information
processing being performed are more tractable in a simplified and at the same time quantitatively specified model. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
299 |
|
The VisNet
model contains a series a competitive networks, organized in
our hierarchical layers,
exhibiting mutual inhibition over a short range within each
layer.
These networks allow combinations of
features or inputs occurring in a given spatial arrangement to be learned by neurons, ensuring that higher order spatial properties of
the input stimuli are represented in the network. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
299 |
|
The VisNet
model has a convergent series of connections from a localized
population of cells in preceding
layers to each cell of the following layer, thus allowing the receptive
field size of cells to increase through the visual processing
areas all layers. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
299 |
|
The VisNet
model uses a modified Hebb-like learning rule incorporating a temporal trace of each cell's previous activity,
which will enable the neurons to learn
transform invariances. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
299 |
|
The learning
rule implemented in VisNet
simulation utilizes the spatio-temporal constraints placed upon the behavior of real
world objects to learn about natural object transformations. By presenting consistent sequences of
transforming objects the cells in the network can learn to respond to the same object through all of its naturally
transformed states. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
301 |
|
The VisNet
network consists of a series of four layers, constructed such that
the convergence of
information from the most disparate parts of the network's input layer can potentially influence firing in a single neuron in the final layer. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
324 |
|
The issue of feature
binding, and a solution. |
|
23 |
Rolls; Memory, Attention, and Decision-Making |
325 |
|
Syntactic binding of separate neuronal assemblies by synchronization. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
325 |
|
Synchronization to implement syntactic binding has a number of disadvantages and
limitations. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
325 |
|
Synchronization does not by itself define the spatial
relations between the features being bound, so is not, just as binding mechanism, adequate for shape recognition. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
325 |
|
When stimulus-dependent
temporal synchronization has been rigorously
tested with information theoretic approaches, it is then found that most of
the information available is in the number of spikes, with rather little, less than 5% of the total information, in stimulus-dependent synchronization. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
325 |
|
The implication of research
results is that any stimulus dependent synchrony that is present is not quantitatively important as
measured by information theoretic analyses under natural scene conditions when feature binding, segregation
of objects in the background, and attention are required. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
325 |
|
The disadvantages
of synchronization
have been found for the inferior temporal cortex, a brain region where features are put together to form a representations of
objects, and where attention has strong effects. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
325 |
|
In connection with the rate codes, it should be noted that
a rate code implies using the number of spikes that arrive in a given time, and that this time can be very
short, as little as 20-50
ms, for very useful
amounts of information to be made available from a population of neurons. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
In the context of the visual simulation program VisNet,
and how the real visual system may operate to implement object recognition, the use of synchronization does not appear to match the way in which the visual system is organized. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
The primate uses a considerable part of its
cortex, perhaps 50% in
monkeys, or visual
processing. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
The solution adopted by the real visual system may be one
which relies on many
neurons with simpler
processing than arbitrary
syntax implemented by synchronous
firing of separate
assemblies suggests. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
A network that forms low-order combinations of features represented in previous
layers, is very demanding in terms of the number of neurons required, and this matches what is found in the primate visual system. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
Binding of features and their relative spatial position by feature combination neurons. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
By forming neurons that respond to combinations of a few features in the correct spatial arrangement, the
advantages for syntactic binding are obtained, yet without the
combinatorial explosion that would result if the feature combination neurons responded to combinations of many
input features so producing potentially very specifically tuned neurons
that very rarely responded. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
Invariant representations are developed in the next layer from these feature combination neurons which
already contain evidence on their local spatial
arrangement of features. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
326 |
|
Finally, in later
layers, only one stimulus would be specified by the particular
set of low order featured combination neurons present, even though each feature
combination neuron would itself be somewhat invariant. |
|
0 |
Microphone |
373 |
|
The full view-invariant
recognition of objects that occurs even when the objects share the same features,
such as color, texture, etc., is an especially computationally
demanding task, which
the primate visual
system is able to perform with its highly developed temporal lobe cortical visual areas. |
|
47 |
Rolls; Memory, Attention, and Decision-Making |
375 |
|
There are a
number of different short-term memory systems, each implemented in a different cortical area. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
375 |
|
A particular kind of short-term memory can be
implemented with subpopulations of neurons that show maintained activity in a delay period, while a stimulus or event
is being remembered. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
375 |
|
This kind of short-term
memory may operate as an autoassociative attractor network. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
375 |
|
The actual autoassociation could be implemented by autoassociatively
modifiable synapses between connected pyramidal cells within an
area, or by the forward and backward connections between adjacent cortical areas in a hierarchy. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
375 |
|
One short-term
memory system is in the dorsolateral prefrontal cortex,
area 46. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
375 |
|
There is an analogous short-term memory system in a more dorsal and posterior part of the prefrontal cortex involved in remembering the position in visual space to which eye movement (a saccade) should be made. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
375 |
|
Another short-term
memory system is implemented in inferior temporal visual cortex,
especially more ventrally toward their perirhinal cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
377 |
|
Another short-term
memory system is human auditory--verbal short-term
memory, which appears to be implemented in the left hemisphere at the junction of the temporal, parietal, and occipital lobes. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
377 |
|
Patients with damage to the auditory--verbal short-term memory system are described clinically as showing conduction aphasia, in that they cannot repeat a heard string of words. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
Prefrontal cortex short-term memory networks, and
their relation to temporal and parietal perception networks |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
A common way that the brain uses
to implement a short-term memory is to maintain
the firing of neurons during a short memory period after the end of a stimulus. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
In the inferior
temporal cortex, this firing may be maintained for a few hundred milliseconds. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
In more ventral
temporal cortical areas such as the entorhinal cortex, the firing may be maintained for longer periods. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
In the dorsolateral and inferior convexity prefrontal
cortex the firing of
the neurons may be related to the memory of spatial responses or objects or both. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
The firing may be maintained by the operation of associatively
modified recurrent collateral connections between the nearby pyramidal cells producing attractor states in autoassociative networks. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
For the short-term
memory to be maintained during periods in which new
stimuli are to be
perceived, there must be separate networks for the perceptual and short-term memory functions. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
Two coupled networks, one in the inferior temporal
visual cortex for perceptual
functions, and another in the prefrontal cortex for maintaining the short-term memory during intervening stimuli, provide a
precise model for the interaction of perceptual and short-term memory systems. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
378 |
|
The ability to provide multiple separate short-term attractor memories provides the
basis for the dorsolateral prefrontal cortex functions in planning. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
379 |
|
A short-term
memory autoassociation network in the prefrontal cortex could hold active a working memory representation by maintaining its firing in an attractor state. (diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
383 |
|
Computational necessity for a separate, prefrontal cortex, short-term memory system. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
399 |
|
Attentional effects in the
absence of visual stimulation |
|
16 |
Rolls; Memory, Attention, and Decision-Making |
401 |
|
A basic computational module for
biased competition |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
402 |
|
Neurodynamical architecture of a
model of spatial and object-based attention. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
411 |
|
Role of attention and object recognition and visual search. |
|
9 |
Rolls; Memory, Attention, and Decision-Making |
414 |
|
Dynamics of
spatial attention and object recognition. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
416 |
|
Dynamics of
object attention and visual search. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
417 |
|
Neuronal and biophysical
mechanisms of attention. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
421 |
|
Serial
versus Parallel
search. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
421 |
|
Preattentive pop-out |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
424 |
|
Binding problem in perception -- how we specify what goes with
what and where, in order to achieve the perception of a coherent integration of shape, color, movement, and size
in individual objects. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
429 |
|
Linking computational and neurophysiological data on attention. |
|
5 |
Rolls; Memory, Attention, and Decision-Making |
429 |
|
The neglect
syndrome. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
430 |
|
A model of visual spatial neglect. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
437 |
|
Disengagement
of attention in neglect. |
|
7 |
Rolls; Memory, Attention, and Decision-Making |
438 |
|
Extinction
and visual search. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
442 |
|
In the attention model, control is performed by the
information loaded into prefrontal cortex
short-term memories, biasing early visual cortical spatial and object processing areas by backprojections. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
442 |
|
Auditory -- verbal short-term memory system in humans (which using rehearsal holds on-line a set of approximately 7 chunks of information), in which
may be located in the cortex at the junction of the left
parieto-occipito-temporal areas. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
524 |
|
Dual routes to the initiation of actions in response to rewarding and punishing stimuli. (diagram) |
|
82 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
Neural Network Models |
|
19 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
Pattern association memory |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
Neural network models are needed in order to provide a basis for understanding the processing and memory functions performed by neuronal networks in the brain. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
Neural networks used by the parts of the brain involved in memory, attention, decision-making, and
the building of perceptual representations. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
Understanding the neural network models provides a
basis for understanding the theories of how different
types of memory
functions are performed. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
Synaptic plasticity and the rules by which synaptic
strength is modified is based on studies with long-term potentiation. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
Network models emphasized here utilize a local
learning rule, i.e. a rule for synaptic modification, in which the
signals needed to alter
the synaptic strength
are present in pre- and post-synaptic neurons. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
543 |
|
The issue of biological
plausibility endorses the networks described
here, contrasting with less biologically plausible
networks such as multilayer
backpropagation of error networks. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
545 |
|
Learning |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
546 |
|
Recall |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
552 |
|
The importance of distributed representations for pattern associators. |
|
6 |
Rolls; Memory, Attention, and Decision-Making |
552 |
|
A distributed
representation is one which the firing or
activity of all elements in the vector is used to encode a particular stimulus. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
552 |
|
A local
representation is one in which all of the information that a
particular stimulus or event has occurred is provided by the activity of one of the neurons or elements in
the vector. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
552 |
|
If a single-cell
local representation did exist it might be called
a "grandmother cell." |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
552 |
|
When the activity of a number of cells must be taken into account to represent
a stimulus, then the representation is sometimes
described as using ensemble encoding. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
552 |
|
For associative
memories, generalization and graceful degradation are only implemented if the representation
is distributed. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
552 |
|
Graceful degradation and generalization are dependent on distributed
representations. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
553 |
|
Speed |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
553 |
|
Recall is very fast in a real neural network, because the
conditioned stimulus input firings can be applied simultaneously to the synapses, and the activation can be accumulated in one or two time constants of the dendrite (e.g. 10-20 ms) |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
553 |
|
Learning is
fast ('one-shot') and
pattern associators,
in that a single pairing of the conditioned stimulus and the unconditioned stimulus enables the
association to be learned. There is no need to repeat the pairing in order to discover over many trials the appropriate mapping. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
553 |
|
Co-occurrence
or near simultaneity
of CS and the UCS is required for periods of his
little as 100 ms,
with the expression of the synaptic modification being present within typically a
few seconds. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Autoassociation or Attractor Memory |
|
7 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Autoassociative memories or attractor neural networks, store memories, each one of which is represented by a pattern of neural activity. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
The memories of autoassociative or attractor neural networks are stored in the
recurrent synaptic
connections between the neurons of the network. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Autoassociative networks can recall the appropriate memory from the
network when provided with a fragment of one of the memories. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
A feature of autoassociative
memory is that it is content
addressable, i.e. the information
in the memory can be accessed if just the contents of the memory (or a part of the contents of the memory) are used. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Autoassociation memory can be used as a short-term memory, and which iterative processing around the recurrent collateral
connection little keeps a representation active by continuing neuronal firing. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
The short-term
memory reflected in continuing
neuronal firing for several
hundred milliseconds after a visual stimulus is
removed, which is president in visual cortical
areas such as the inferior
temporal visual cortex, is probably implemented
by autoassociation memory. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Autoassociation memories also appeared to be used in a
short-term memory role in the prefrontal cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
The temporal
visual cortical areas have connections to the ventral lateral prefrontal cortex which help to implement the short-term
memory for visual
stimuli. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
The parietal
cortex has
connections to the dorsolateral prefrontal cortex for the short-term memory of spatial responses. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
The short-term
memory connections
between prefrontal cortex, temporal visual
cortical areas, and parietal
cortex provide a mechanism that enables attention to be maintained through
backprojections from
the prefrontal cortex areas to the temporal and parietal areas that send projections to the prefrontal cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Autoassociation networks implemented by recurrent
collateral synapses between cortical pyramidal cells provide a
mechanism for constraint satisfaction and also noise reduction, whereby the firing of neighboring neurons can be taken
into account in enabling the network to settle into a state that reflects all of the details of the inputs activating the population of connected neurons. |
|
|
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Attractor networks are also effectively implemented by virtue of the forward and backward connections between cortical areas. |
|
|
Rolls; Memory, Attention, and Decision-Making |
560 |
|
An
autoassociation network with rapid synaptic plasticity can learn each memory in one trial. |
|
|
Rolls; Memory, Attention, and Decision-Making |
560 |
|
Because of its 'one-shot' rapid learning, and
ability to complete,
an autoassociation network is well suited for episodic memory storage, in which each past episode must be stored and recalled later from a fragment, and kept separate from other episodic memories. |
|
|
Rolls; Memory, Attention, and Decision-Making |
562 |
|
Analysis of the operation of autoassociation networks |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
564 |
|
Completion [Gestalts] |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
564 |
|
Perhaps the most important and
useful property of autoassociation networks is that they complete an incomplete input vector allowing recall of a whole memory from a fraction of it. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
564 |
|
Graceful Degradation or Fault
Tolerance |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
565 |
|
Prototype extraction, extraction of central tendency, and
noise reduction |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
565 |
|
Distributed information storage in a neuronal network such as an autoassociator stores the autocorrelation
components of an input
vector that build up via learning in the synaptic matrix with repeated presentations of the input exemplars. These autocorrelation components
represent the average correlation between the different elements of the input vector, and this is highest for the central
tendency or prototype. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
565 |
|
Recall is very fast on each neuron on a single iteration, because the pattern on the axons can be applied simultaneously to the synapses, and the activation can be accumulated in one or two time constants of the dendrite (e.g. 10-20 ms) |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
565 |
|
If the neurons are analyzed and modelled as 'integrate and fire' neurons, then the network can effectively 'relax'
into its recall state very
rapidly, in one or two
time constants of the synapses, corresponding to perhaps 20 ms in the brain. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
566 |
|
One factor in this rapid dynamics of autoassociative
networks is that with some spontaneous activity, some of the
neurons in the network are close to threshold already before the recall cue is applied,
and hence some of the neurons are very quickly pushed by the recall cue into firing, so that information starts to be exchanged very rapidly (within 1-2 ms through the modified synapses by the neurons in the network. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
566 |
|
The progressive
exchange of information starting early on within what would otherwise be thought
about as an iteration period (of perhaps 20 ms, corresponding to a neuronal
firing rate of 50 spikes/s) is the mechanism accounting for rapid recall in an autoassociative neuronal network made
biologically realistic
in this way |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
566 |
|
Networks with recurrent connections, not just
autoassociators, can operate
much faster than simple models that follow discrete dynamics and is probably
a major factor enabling these networks to provide some of the building blocks of brain function. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
566 |
|
Learning is fast, 'one-shot' in that a single presentation of an input pattern enables the association between the activation of the dendrites and the firing of the recurrent collateral axons to be learned. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
566 |
|
Repeated presentation with small variations of the pattern
vector is used to obtain the properties of prototype extraction, extraction of
central tendency, and noise reduction, because these
arise from the averaging process produced by storing very similar
patterns in the network. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
568 |
|
The main factors that determine
the maximum number of memories
that can be stored in
an autoassociative network are thus the number of
connections on each neuron devoted to the recurrent collaterals, and the sparseness of the representation. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
568 |
|
Increasing
the number of neurons (without increasing the number of
connections per neuron), does not increase the number of different patterns that
can be stored,
although it may enable simpler encoding of the firing patterns, for
example more orthogonal encoding. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
568 |
|
The environmental context in which learning occurs can be very
important factor that affects retrieval in humans and other animals. Placing the subject back into
the same context in
which the original learning occurred can greatly facilitate retrieval. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
568 |
|
The effects that mood has on memory including visual memory retrieval may be
accounted for by backprojections from brain regions such as the amygdala and orbitofrontal cortex in which the current mood, providing a context, is represented, to brain regions
involved in memory such as perirhinal
cortex, and in visual representations such as the inferior temporal visual cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
569 |
|
Context effects will be especially
important at late
stages of memory or information processing systems in the brain, for there
information from a wide variety of modalities will be mixed, and some of that information could reflect the context in which the learning takes place. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
569 |
|
Context effects may be strong in the hippocampus, which is implicated in the memory
of recent episodes, and which receives inputs derived from most to the cortical
information processing streams, including those
involved in space. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
569 |
|
Memory for Sequences |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
570 |
|
Use of autoassociation
networks in the brain |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
571 |
|
Competitive networks, including
self-organizing maps |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
573 |
|
Feature discovery by
self-organization |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
573 |
|
Removal of redundancy |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
574 |
|
Orthogonalization and
categorization |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
575 |
|
Sparsification |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
577 |
|
Comparison to principal
component analysis (PCA) and cluster analysis |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
578 |
|
Utility of competitive networks
in information processing by the brain |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
578 |
|
Feature analysis and
preprocessing |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
578 |
|
Neurons
that respond to correlated combinations of their inputs can be described in feature analyzers. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
578 |
|
The power of competitive
networks in multistage
hierarchical processing builds combinations of what is found at earliest stages, and thus
effectively builds higher order representations. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
578 |
|
Competitive networks can learn about individual objects even when multiple objects are presented simultaneously, provided that each object is represented
several times more frequently than it is paired with any other individual object. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
578 |
|
Learning in
competitive networks
is primarily about forming representations of objects defined by a high correlation of coactive features in the input space. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
578 |
|
Removal of redundancy |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
579 |
|
Orthogonalization |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
579 |
|
Sparsification |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
579 |
|
Brain systems
in which competitive networks may be used for orthogonalization and sparsification. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
579 |
|
Guidance of competitive learning |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
579 |
|
Although competitive
networks are primarily
unsupervised networks,
it is possible to influence the categories found by supplying a second input. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
582 |
|
Topographic map formation |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
586 |
|
Invariance learning by competitive networks |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
591 |
|
Large competitive nets |
|
5 |
Rolls; Memory, Attention, and Decision-Making |
593 |
|
Continuous attractor networks |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
604 |
|
Network dynamics: the integrate-and-fire approach |
|
11 |
Rolls; Memory, Attention, and Decision-Making |
610 |
|
An integrate-and-fire implementation |
|
6 |
Rolls; Memory, Attention, and Decision-Making |
611 |
|
Simulation of
fMRI signals: hemodynamic convolution of synaptic activity |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
613 |
|
The speed of
processing of one-layer attractor
networks with integrate-and-fire neurons. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
Is the information that must be stored present in the firing rates or is it present in
the synchronized firing
of subsets of neurons? |
|
46 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
If the information is present in the firing rates, how much information is available from the spiking activity in a short period, e.g. 20 or 50 ms? |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
For each
stage of the cortical processing to operate quickly (e.g. 20 ms), it
is necessary for each stage to be able to read the code being provided by the previous
cortical area within this
order of time. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
Understanding the neural code is fundamental to
understanding how each stage of the processing works in the brain, and for understanding the speed
of processing at each
stage. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
We can address the richness of the representation by
understanding the differences in the responses of different neurons, and the impact this has on the amount
of information that is encoded. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
We must seek
understanding at the level of the activity of single neurons and of populations of single neurons, and understanding at this neuronal level
(rather than at the level of thousands or millions
of neurons as revealed by the functional imaging) is essential
for understanding brain computation. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
Information theory provides a means for quantifying how much neurons communicate to other neurons, and thus provide a quantitative approach to
fundamental questions about information processing in the brain. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
659 |
|
To investigate the speed of information
transmission, one must define and measure information rates from neuronal responses. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
662 |
|
Information
sources, information
channels, and information measures. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
663 |
|
The information
transmitted by a channel can range from zero to the lower of two independent upper bounds: the entropy
of the source, and the capacity
of the channel. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
663 |
|
The information
carried by neuronal
response and its averages. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
664 |
|
Mutual information emphasizes that responses tell us about stimuli just as much as stimuli tell us about responses. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
666 |
|
Information retrieved from an autoassociative memory. |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
668 |
|
Estimating the information carried by neuronal responses |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
683 |
|
The sparseness out the distributed encoding used by the brain. |
|
15 |
Rolls; Memory, Attention, and Decision-Making |
685 |
|
Firing rate distribution of a single neuron in the temporal visual cortex (diagram) |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
688 |
|
The peak at low but nonzero rates may be related to the low firing
rate spontaneous activity that is typical of many cortical neurons. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
689 |
|
A neuron with inputs from the inferior temporal visual
cortex will receive an exponential
distribution of firing
rates on its afferents. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
689 |
|
At the level of single neurons, an exponential probability density
function is consistent with minimizing energy utilization, and maximizing information transmission,
for a given mean firing rate. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
690 |
|
Population sparseness |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
691 |
|
Population sparseness -- firing rates of a population of inferior temporal cortex neurons to
any one stimulus from
a set of 20 face and non-face stimuli. (diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
692 |
|
Comparisons
of sparseness between areas -- the hippocampus, insula, orbitofrontal cortex, and amygdala. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
693 |
|
The information from single neurons. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
697 |
|
The information from single neurons -- temporal codes versus rate codes within the spike trains of a single neuron. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
698 |
|
The information from single neurons -- speed of
information transfer |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
702 |
|
How rapid information can be read from neurons is crucial for understanding how any stage of
cortical processing operates, given that each stage includes associative or competitive network processes that require the code to be read before you can pass useful output to the next stage of processing. |
|
4 |
Rolls; Memory, Attention, and Decision-Making |
702 |
|
A rapid
readout of information from any one stage is important, for the
ventral visual system
is organized as a hierarchy of cortical areas, and the neuronal response
latencies are approximately 100 ms in inferior temporal visual cortex,
and 40-50 ms in the primary visual cortex, allowing
only 50-60 ms of
processing time for V1 -- V2 -- V4 -- inferior temporal cortex. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
702 |
|
There is much evidence that the time required for each stage of processing is relatively short. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
702 |
|
Visual stimuli presented in succession approximately 15 ms apart can be separately identified. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
703 |
|
The number
of spikes in a fixed
time window over which a postsynaptic neuron could integrate information is a more
realistic code. This time might be of
the order of 20 ms
for single receiving neuron, or much longer if the receiving neurons are connected by recurrent
collateral associative synapses and so can integrate information over time. |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
703 |
|
Although the number
of spikes in a short
time window, e.g. 20
ms is likely to be 0,
1, or 2, the information available may be more than that from the first spike alone. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
705 |
|
Speed of information availability in the inferior temporal visual
cortex. Cumulative single
cell information.
(diagram) |
|
2 |
Rolls; Memory, Attention, and Decision-Making |
705 |
|
An attractor
network might be able to integrate the information
arriving over a long time period of several
hundred milliseconds. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
705 |
|
A single-layer pattern association network might
only be able to integrate the information over the time
constants of the synapses and cell membrane, which might be of the order of 15-30
ms. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
705 |
|
In a hierarchical
processing system such as the visual cortical areas, there may
only be a short time
during which each stage
may decode the information from the preceding stage, and then pass on information sufficient to support recognition to the next stage. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
706 |
|
Speed of information availability in the inferior temporal visual
cortex. Cumulative multiple
cell information.
(diagram) |
|
1 |
Rolls; Memory, Attention, and Decision-Making |
706 |
|
With a population
of neurons, having just one spike from each neuron can allow considerable information to be read if only a limited (e.g. 20-50
ms) is available for the readout. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
709 |
|
The information from multiple cells -- independent information versus redundancy across cells. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
715 |
|
The information from multiple cells -- the effects of cross correlations
between cells. |
|
6 |
Rolls; Memory, Attention, and Decision-Making |
718 |
|
Research results are consistent
with the hypothesis that feature binding is implemented by neurons that respond to features in the correct relative spatial locations, and not
by temporal synchrony and attention. |
|
3 |
Rolls; Memory, Attention, and Decision-Making |
718 |
|
Even if stimulus
dependent synchrony was useful for grouping, it would not without
much extra machinery be useful for binding the relatives spatial positions of features within an object, or for that matter of the position
of objects in a scene, which appear to be encoded in a
different way. |
|
0 |
Rolls; Memory, Attention, and Decision-Making |
|
|
|
|
|
|
|
|
|
|
|