| Gluck & Myers; Gateway to Memory - Modeling the Hippocampus | |||||
| Book | Page | Topic | |||
| Gluck & Myers; Gateway to Memory | 12 | Subfields of the hippocampus, CA1 through CA4 | |||
| Gluck & Myers; Gateway to Memory | 12 | Hippocampus nearby structures -- dentate gyrus, subiculum, entorhinal cortex, perirhinal cortex, parahippocampal cortex, amygdala | 0 | ||
| Gluck & Myers; Gateway to Memory | 13 | Hippocampal region refers to a subset of medial temporal structures -- hippocampus, dentate gyrus, subiculum, entorhinal cortex. | 1 | ||
| Gluck & Myers; Gateway to Memory | 13 | Fornix, a fiber pathway connecting the hippocampus to subcortical structures, is often included as part of the hippocampal region. | 0 | ||
| Gluck & Myers; Gateway to Memory | 13 | Exact functions of the hippocampal region remain a subject of contentious debate. | 0 | ||
| Gluck & Myers; Gateway to Memory | 14 | Neuroscientists now agree that the hippocampus has something to do with learning and memory, but there is little consensus about exactly what the hippocampus is doing when we learn and store new memories. | 1 | ||
| Gluck & Myers; Gateway to Memory | 14 | Much of our understanding of the hippocampal region's role in learning and memory comes from individuals who have suffered damage to the medial temporal lobes. | 0 | ||
| Gluck & Myers; Gateway to Memory | 14 | One of the most famous individuals with hippocampal region damage was a young man HM whose epileptic seizures originated in the hippocampi. Doctors removed an 8 cm segment from each of his temporal lobes, including two thirds of each hippocampus. HM's ability to acquire new memories had been devastated. | 0 | ||
| Gluck & Myers; Gateway to Memory | 15 | Although HM's intelligence, language skills, and personality are largely as they were before the surgery, he has essentially no memories for any events of the last decades of his life. | 1 | ||
| Gluck & Myers; Gateway to Memory | 15 | HM does have a reasonably normal memory for events that occurred at least two years before his surgery. | 0 | ||
| Gluck & Myers; Gateway to Memory | 15 | Although HM can participate in a conversation, a few minutes later he will have lost all memory of it. | 0 | ||
| Gluck & Myers; Gateway to Memory | 15 | H.M. cannot learn the names or faces of people who visit him regularly. | 0 | ||
| Gluck & Myers; Gateway to Memory | 15 | Even the doctors and psychologists who have worked with H.M. for over 45 years must reintroduce themselves to him each time they meet. | 0 | ||
| Gluck & Myers; Gateway to Memory | 15 | Since H.M. himself has aged sense surgery, he does not recognize his own face when he is shown a current picture of himself. | 0 | ||
| Gluck & Myers; Gateway to Memory | 15 | HM is painfully aware of his own problems and has described his life as constantly waking from a dream he can't remember. | 0 | ||
| Gluck & Myers; Gateway to Memory | 15 | HM's condition is known as anteriorgrade amnesia, the inability to form new memories. | 0 | ||
| Gluck & Myers; Gateway to Memory | 16 | Unilateral removal of a hippocampus may still be done in cases of severe epilepsy, but this usually results in a much milder memory impairment than seen in HM. | 1 | ||
| Gluck & Myers; Gateway to Memory | 17 | Transient loss or reduction of oxygen (called anoxia or hypoxia) is a frequent cause of amnesia, because hippocampal cells seem particularly sensitive to oxygen deprivation. | 1 | ||
| Gluck & Myers; Gateway to Memory | 17 | Damage to or disruption of the hippocampal region may cause anteriorgrade amnesia -- a devastating loss of new memory formation, with a relative sparing of intelligence, personality, skill learning, and old memories. | 0 | ||
| Gluck & Myers; Gateway to Memory | 31 | Classical Conditioning and the Hippocampus | 14 | ||
| Gluck & Myers; Gateway to Memory | 32 | Schematic of classical conditioning -- unconditioned stimulus (US), conditioned stimulus (CS) (diagram) | 1 | ||
| Gluck & Myers; Gateway to Memory | 82 | Representation and Generalization | 50 | ||
| Gluck & Myers; Gateway to Memory | 82 | Psychologists have long understood that a fundamental property of animal and human learning is generalization, the degree to which learning about one stimulus transfers to other stimuli. | 0 | ||
| Gluck & Myers; Gateway to Memory | 84 | Generalization is critical for applying prior experience to new situations, without requiring fresh learning about every new instance. | 2 | ||
| Gluck & Myers; Gateway to Memory | 85 | A major challenge for learning theorists has been to understand how differences in stimulus similarity affect learning and generalization behaviors. | 1 | ||
| Gluck & Myers; Gateway to Memory | 86 | Animals and people tend to assume that to stimuli that are physically similar will have similar consequences and generalize accordingly. | 1 | ||
| Gluck & Myers; Gateway to Memory | 86 | There is also a need for specificity in learning, too allowed superficially similar stimuli to be associated with different responses | 0 | ||
| Gluck & Myers; Gateway to Memory | 86 | In general, there is always a trade-off between generalization and specificity in learning. | 0 | ||
| Gluck & Myers; Gateway to Memory | 86 | The brain generally represents information using distributed representations, in which each stimulus is encoded by many different neurons and each neuron may respond to conjunctions of features that may be present in many different stimuli. | 0 | ||
| Gluck & Myers; Gateway to Memory | 87 | Distributed representation is efficient because a large number of stimuli can be processed by smaller number of neurons, each of which encodes some features of the stimuli. | 1 | ||
| Gluck & Myers; Gateway to Memory | 87 | Distributed representations have the advantage that if some of the units are lost or degraded, the remaining units may be able to provide enough information to represent the stimuli adequately. | 0 | ||
| Gluck & Myers; Gateway to Memory | 87 | The drawback of a distributed representation is that recognizing a particular stimulus may require integrating information from many different neurons that encode the stimulus features. | 0 | ||
| Gluck & Myers; Gateway to Memory | 87 | Neuroscientists have concluded that the brain most likely uses distributed representations to encode information. | 0 | ||
| Gluck & Myers; Gateway to Memory | 87 | Distributed representation uses a set of overlapping elements to encode input stimuli. | 0 | ||
| Gluck & Myers; Gateway to Memory | 87 | Nodes in the neural network are, in general, laid out topographically, meaning that nodes responding to physically similar stimuli are physically next to each other in the network. | 0 | ||
| Gluck & Myers; Gateway to Memory | 87 | The degree of overlap between the representations of two stimuli reflects their physical similarity. | 0 | ||
| Gluck & Myers; Gateway to Memory | 111 | Unsupervised Learning -- Autoassociative Networks and the Hippocampus | 24 | ||
| Gluck & Myers; Gateway to Memory | 114 | Hebbian learning is unsupervised, meaning that it does not depend on a special teaching signal. | 3 | ||
| Gluck & Myers; Gateway to Memory | 114 | Weight change is automatic in Hebb's rule and depends only on conjoint activity in pairs of nodes. | 0 | ||
| Gluck & Myers; Gateway to Memory | 115 | The ability to remember patterns is one mechanism by which the brain might store memories of past events. | 1 | ||
| Gluck & Myers; Gateway to Memory | 115 | Once a pattern has been stored, activation in any one node will produce activation in the other nodes of a pattern. | 0 | ||
| Gluck & Myers; Gateway to Memory | 115 | Even after the external input is turned off, the pattern (stored as an assembly of active nodes) remains for some time, until activation gradually dies away. In this way, superficially unrelated but temporally coincident stimuli can be bound together into a unified memory. | 0 | ||
| Gluck & Myers; Gateway to Memory | 115 | The most interesting property of an autoassociative network -- given a partial or incomplete version of the stored memory, an autoassociative network can retrieve the entire stored pattern -- this is called pattern completion. | 0 | ||
| Gluck & Myers; Gateway to Memory | 116 | A variation of a pattern completion property of an autoassociatiave network is a process of pattern recognition -- the ability to take an arbitrary input and retrieve the stored pattern that is most similar to that input. | 1 | ||
| Gluck & Myers; Gateway to Memory | 117 | The twin features of pattern completion and pattern recognition has led to many engineering applications of autoassociative networks. | 1 | ||
| Gluck & Myers; Gateway to Memory | 117 | Hippocampal Anatomy and Autoassociation | 0 | ||
| Gluck & Myers; Gateway to Memory | 117 | Most theories that have tried to map from hippocampal anatomy to behavioral function have focused on a particular subfield within the hippocampus -- field CA3. | 0 | ||
| Gluck & Myers; Gateway to Memory | 117 | One primary input to CA3 comes from entorhinal cortex, carrying highly processed information about all kinds of sensory input. This pathway is called the perforant path, since its fibers physically perforate the dentate gyrus to reach CA3. | 0 | ||
| Gluck & Myers; Gateway to Memory | 118 | A secondary path from the entorhinal cortex synapses in dentate gyrus before proceeding on to CA3. The connections from dentate gyrus to CA3 are called mossy fibers, and they make sparse, large, and presumably very powerful synapses onto CA3 neurons. | 1 | ||
| Gluck & Myers; Gateway to Memory | 118 | CA3 neurons process the information and send their outputs on to hippocampal field CA1 and from there out of the hippocampus. | 0 | ||
| Gluck & Myers; Gateway to Memory | 118 | One of the most striking features of CA3 anatomy is a high degree of internal recurrency, meaning that CA3 neurons send axons not only out of CA3, but also back to synapse on other CA3 neurons. | 0 | ||
| Gluck & Myers; Gateway to Memory | 118 | Recurrency feedback is a general principle throughout the brain, but it is dramatically heightened in CA3. | 0 | ||
| Gluck & Myers; Gateway to Memory | 118 | Each CA3 pyramidal neuron in the rat may receive about 4000 synapses from entorhinal inputs but up to about 12,000 synapses from other CA3 cells. | 0 | ||
| Gluck & Myers; Gateway to Memory | 118 | Each CA3 pyramidal neuron receives inputs from about 4% of all other CA3 pyramidal neurons. | 0 | ||
| Gluck & Myers; Gateway to Memory | 119 | The 4% recurrency is orders of magnitude higher than the degree of internal recurrency that is observed elsewhere in the brain. | 1 | ||
| Gluck & Myers; Gateway to Memory | 119 | The connections between CA3 neurons are modifiable by LTP in much the same manner as Hebb proposed. | 0 | ||
| Gluck & Myers; Gateway to Memory | 119 | LTP was originally discovered by researchers studying synapses in the hippocampal region. | 0 | ||
| Gluck & Myers; Gateway to Memory | 119 | A Hippocampal model assumes that CA3 pyramidal neurons form an autoassociative network in which external inputs (from entorhinal cortex and dentate gyrus) activate a subset of CA3 neurons. Recurrent collaterals between coactive nodes are strengthened, storing the pattern. | 0 | ||
| Gluck & Myers; Gateway to Memory | 119 | Many of the basic ideas underlying the recurrent hippocampal model have withstood continuing empirical and theoretical analysis and are implicit in most modern models of hippocampus. | 0 | ||
| Gluck & Myers; Gateway to Memory | 124 | Autoassociative models of hippocampus have considerable power for describing the hippocampal regions role in episodic memory formation. | 5 | ||
| Gluck & Myers; Gateway to Memory | 148 | The hippocampal region is not the final site of memory storage as evidence by empirical data showing that old, well established memories can survive hippocampal-region damage. | 24 | ||
| Gluck & Myers; Gateway to Memory | 149 | A cerebellum model shows that stimulus inputs are processed by various primary cortical areas and then travel to the cerebellum via structure of the bonds. The cerebellum learns to map from these inputs to an output that derives a condition motor response. | 1 | ||
| Gluck & Myers; Gateway to Memory | 149 | The cerebellum model also contains an inhibitory feedback loop through the inferior olive that manages the era between the actual response (which is a prediction of unconditioned stimulus (US) arrival) and whether the US actually arrived. | 0 | ||
| Gluck & Myers; Gateway to Memory | 165 | The neurophysiological evidence currently available is remarkably consistent with the implication suggesting that hippocampal neuronal representations can and do change to reflect associations between stimuli and rewards. | 16 | ||
| Gluck & Myers; Gateway to Memory | 175 | Several prominent theories assume that the hippocampal region is involved in stimulus configuration (or chunking), whereby a set of co-occurring stimuli come to be treated as a unary whole (or configuration) that can accrue associations. | 10 | ||
| Gluck & Myers; Gateway to Memory | 177 | The hippocampal region has been implicated in contextual processing. The hippocampus has been proposed as a source for contextual tags to memories, which identify the spatial and temporal settings in which events occur. | 2 | ||
| Gluck & Myers; Gateway to Memory | 177 | Context is usually defined as the set of background cues that are present during a learning experience. | 0 | ||
| Gluck & Myers; Gateway to Memory | 177 | Patients with medial temporal lobe amnesia can often acquire new information but not recall the spatial and temporal context in which it occurred. | 0 | ||
| Gluck & Myers; Gateway to Memory | 177 | The nondeclarative learning that is often preserved in amnesia tends to be acquired slowly, over many trials, and is less strongly associated with any particular context. | 0 | ||
| Gluck & Myers; Gateway to Memory | 179 | The hippocampal region has a role in maintaining information over a course of a few minutes -- this kind of memory is often called intermediate term memory (as distinct from the short-term memory that is we used to remember a telephone number by constant rehearsal or long-term memory, which can last for years). | 2 | ||
| Gluck & Myers; Gateway to Memory | 179 | Researchers have suggested that the intermediate-term memory buffer can be specifically localized within the parahippocampal region, including entorhinal, perrirhinal, and parahippocampal cortices. | 0 | ||
| Gluck & Myers; Gateway to Memory | 179 | The hippocampal region may be involved in constructing new representations that can press together stimuli that cooccur or similar in meaning; this compression could apply equally to stimuli that are superficially dissimilar, and to those that are separated in time or in space. | 0 | ||
| Gluck & Myers; Gateway to Memory | 189 | Cortico-Hippocampal Interaction and Contextual Processing | 10 | ||
| Gluck & Myers; Gateway to Memory | 215 | The hippocampal region is the culmination of a long and intricate processing chain. | 26 | ||
| Gluck & Myers; Gateway to Memory | 215 | Sensory inputs from receptors such is retinal transducers and tastebuds travel through the thalamus and into areas of cerebral cortex that are specifically devoted to processing different kinds of sensory information. | 0 | ||
| Gluck & Myers; Gateway to Memory | 215 | Information travels to higher cortical areas, which combine and integrate across sensory modalities, before finally reaching the hippocampal region. | 0 | ||
| Gluck & Myers; Gateway to Memory | 216 | This cerebral cortex is a grade sheet covering most of the mammalian brain and containing the cell bodies of neurons. The output processes of these cells, axons, form the underlying white matter that makes up much of the bulk of the brain in higher species. | 1 | ||
| Gluck & Myers; Gateway to Memory | 216 | Only mammals have six layered cortex; reptiles and birds have a simpler kind of cortex -- sometimes called paleocortex or allocortex -- with only two layers. | 0 | ||
| Gluck & Myers; Gateway to Memory | 216 | Six layered cortex is often called neocortex or isocortex, reflecting the assumption that it developed later in evolution. | 0 | ||
| Gluck & Myers; Gateway to Memory | 216 | There are a few places in the mammalian brain that are also two-layered paleocortex, and these may be evolutionary remnants from which neocortex developed. | 0 | ||
| Gluck & Myers; Gateway to Memory | 217 | Mammalian brains show a variety in size and complexity but also share many features, including the presence of six layered neocortex. The rat brain and the human brain show many of the same structures. | 1 | ||
| Gluck & Myers; Gateway to Memory | 216 | The rats olfactory system is proportionately larger than the human's, while the rats neocortex is only a fraction of the size of the human's. | -1 | ||
| Gluck & Myers; Gateway to Memory | 218 | The cortex of an adult human would measure about 1.5 ft.² if spread out into a flat sheet. | 2 | ||
| Gluck & Myers; Gateway to Memory | 218 | The wrinkled appearance of the human brain reflects the fact that the cortex has to fold to fit inside the confines of the skull. | 0 | ||
| Gluck & Myers; Gateway to Memory | 218 | The rat cortex fits quite comfortably inside the rats skull without wrinkles. | 0 | ||
| Gluck & Myers; Gateway to Memory | 218 | For each sensory modality, the first cortical processing occurs in a specific region -- primary visual cortex (V1) for vision, primary audio cortex (A1) for sounds, etc. | 0 | ||
| Gluck & Myers; Gateway to Memory | 218 | Primary sensory cortex is organized topographically. Each region
of cortex responds
preferentially to a particular
type of stimulus, and neighboring
cortical regions respond to similar
stimuli. . |
0 | ||
| Gluck & Myers; Gateway to Memory | 218 | Primary sensory cortex (S1) is a thin strip of cortex running down each side of the brain in humans. | 0 | ||
| Gluck & Myers; Gateway to Memory | 219 | Primary audio cortex (A1) lies near the top of the temporal lobe in humans and is organized as a topographic map. | 1 | ||
| Gluck & Myers; Gateway to Memory | 219 | Adjoining areas of the A1 respond to similar tone frequencies in an orderly fashion. | 0 | ||
| Gluck & Myers; Gateway to Memory | 219 | The topographic organization of primary sensory cortex seems to be a consistent feature across modalities and across mammalian species. | 0 | ||
| Gluck & Myers; Gateway to Memory | 220 | The output from primary sensory cortex goes to higher-order cortical areas, where the obvious topographic ordering may be lost, or else information may be coded in a topographic manner that researchers don't yet understand. | 1 | ||
| Gluck & Myers; Gateway to Memory | 223 | An unsupervised learning system does not learn to produce any predefined desired output. Instead, the network discovers underlying regularities -- statistically significant features -- of the input it is given. | 3 | ||
| Gluck & Myers; Gateway to Memory | 223 | Unsupervised learning systems are also called self-organizing networks, since they do not depend on an external reinforcement. | 0 | ||
| Gluck & Myers; Gateway to Memory | 223 | Autoassociative networks are one kind of unsupervised network. | 0 | ||
| Gluck & Myers; Gateway to Memory | 223 | Another class of unsupervised network is a competitive network, meaning that the nodes of the network compete with one another for the 'right' to respond to stimuli. | 0 | ||
| Gluck & Myers; Gateway to Memory | 225 | A network may be termed a self-organizing feature map if it forms a topographic representation based on some features of the input. | 2 | ||
| Gluck & Myers; Gateway to Memory | 227 | Self Organizing Feature Maps -- computer algorithms to discover underlying order in a large database. | 2 | ||
| Gluck & Myers; Gateway to Memory | 228 | Speech Processing -- a continuous stream of speech is recognized as a pattern of phonemes, and eventually resulting in translated typewritten text. | 1 | ||
| Gluck & Myers; Gateway to Memory | 232 | There exists a few places in the brain where the cortex begins to change, gradually becoming two-layer paleocortex similar to reptile cortex. | 4 | ||
| Gluck & Myers; Gateway to Memory | 232 | Olfactory cortex is two-layer paleocortex. | 0 | ||
| Gluck & Myers; Gateway to Memory | 232 | The hippocampus is a two-layered sheet of paleocortex, although it is folded-in on itself to create its characteristic "C" shape. | 0 | ||
| Gluck & Myers; Gateway to Memory | 232 | One theory is that hippocampus and paleocortex are remnants of the primitive brain from which more complex neocortex evolved. | 0 | ||
| Gluck & Myers; Gateway to Memory | 232 | The relatively simple organization of paleocortex suggests that it is a logical place to begin exploring how cortical anatomy could give rise to computational function. | 0 | ||
| Gluck & Myers; Gateway to Memory | 233 | Although human olfactory cortex is relatively small, the olfactory cortex of most mammals is much larger, reflecting the importance of odor information to those species. | 1 | ||
| Gluck & Myers; Gateway to Memory | 233 | Dogs have almost 50 times as many olfactory neurons as humans. | 0 | ||
| Gluck & Myers; Gateway to Memory | 233 | Olfaction begins with a thin sheet of olfactory receptor cells, high up in the nasal cavity, called the olfactory epithelium. | 0 | ||
| Gluck & Myers; Gateway to Memory | 237 | The hippocampal region can form new stimulus representations that compress redundant information while differentiating predictive information. | 4 | ||
| Gluck & Myers; Gateway to Memory | 237 | The hippocampus receives highly processed, multimodal information from a whole range of stimulus modalities. | 0 | ||
| Gluck & Myers; Gateway to Memory | 260 | Entorhinal cortex is intermediate in structure between six-layered neocortex and two-layered paleocortex. | 23 | ||
| Gluck & Myers; Gateway to Memory | 260 | From entorhinal cortex, axons project to the dentate gyrus and hippocampus. | 0 | ||
| Gluck & Myers; Gateway to Memory | 260 | The tract from entorhinal cortex to dentate gyrus is known as the perforant path, because these fibers traveled through (perforate) the subiculum to reach their destination. | 0 | ||
| Gluck & Myers; Gateway to Memory | 261 | From dentate gyrus, axons traveled to the hippocampal subfields CA3, which also receives a direct projection from entorhinal cortex. | 1 | ||
| Gluck & Myers; Gateway to Memory | 261 | The combination of strong dentate and weaker entorhinal projections to CA3, together with high recurrency among CA3 neurons, suggests that CA3 might function as an autoassociator. | 0 | ||
| Gluck & Myers; Gateway to Memory | 261 | Information projects from CA3 to hippocampal field CA1, through the subiculum, back through the deep layers of entorhinal cortex, and finally back to the same cortical areas that gave rise to the information in the first place. | 0 | ||
| Gluck & Myers; Gateway to Memory | 261 | The unidirectional flow from entorhinal cortex through dentate gyrus, hippocampus, subiculum back to entorhinal cortex is a primary feature of the circuitry. | 0 | ||
| Gluck & Myers; Gateway to Memory | 265 | Hippocampal field CA3 has received extensive study because of its physical resemblance to an autoassociative network. | 4 | ||
| Gluck & Myers; Gateway to Memory | 265 | Entorhinal cortex has begun to receive attention from researchers: (1) because of its similarity to neocortex and (2) because of suggestions that many behaviors that were previously thought to depend on the hippocampus may actually be mediated by the entorhinal cortex. | 0 | ||
| Gluck & Myers; Gateway to Memory | 266 | Entorhinal cortex represents the highest stage of cortical processing, in which all sensory information converges. | 1 | ||
| Gluck & Myers; Gateway to Memory | 266 | Entorhinal cortex would be a logical place to perform clustering among stimuli in different modalities, or among the multimodal features of a single stimulus. | 0 | ||
| Gluck & Myers; Gateway to Memory | 266 | Superficial layers of entorhinal cortex received highly processed, multimodal stimulus inputs. | 0 | ||
| Gluck & Myers; Gateway to Memory | 266 | Entorhinal cells are grouped together into clusters; within each cluster, cells compete to respond to the input. | 0 | ||
| Gluck & Myers; Gateway to Memory | 266 | Cells that when the competition undergo plasticity, making them more likely to respond to similar inputs in the future. | 0 | ||
| Gluck & Myers; Gateway to Memory | 266 | Losing cells also undergo plasticity, making them less likely to respond to similar inputs. | 0 | ||
| Gluck & Myers; Gateway to Memory | 266 | Losing cells in the competition become more likely to win the competition in response to very different inputs. | 0 | ||
| Gluck & Myers; Gateway to Memory | 266 | The entorhinal network model performs unsupervised clustering of its inputs. | 0 | ||
| Gluck & Myers; Gateway to Memory | 282 | In the same way that entorhinal cortex may perform representational compression, there is emerging evidence that dentate gyrus may perform representational differentiation. | 16 | ||
| Gluck & Myers; Gateway to Memory | 282 | The entorhinal cortex and dentate gyrus together may perform most or all of the representational processing that has been assumed to take place in a hippocampal region. | 0 | ||
| Gluck & Myers; Gateway to Memory | 282 | Other hippocampal region areas, such as CA3 and CA1, may be more involved in short-term storage of information and overseeing its eventual consolidation to cerebral cortex. | 0 | ||
| Gluck & Myers; Gateway to Memory | 287 | Schematic of sensory information flow through cortical areas as envisioned by Edmund Rolls (diagram) | 5 | ||
| Gluck & Myers; Gateway to Memory | 287 | Anatomical pathway by which hippocampal region processing can influence cortical areas. | 0 | ||
| Gluck & Myers; Gateway to Memory | 287 | Edmund Rolls has developed a theory of how feedback projections could allow representations developed in hippocampus to drive cortical storage. | 0 | ||
| Gluck & Myers; Gateway to Memory | 287 | Pyramidal neurons in an area of cortex receive feedforward projections carrying sensory information from earlier cortical areas and also feedback projections from the later cortical areas. | 0 | ||
| Gluck & Myers; Gateway to Memory | 287 | For entorhinal cortex, feedforward inputs detail the highly processed, multimodal features of current input, while feedback inputs carry information about the hippocampal region's representation of this information. | 0 | ||
| Gluck & Myers; Gateway to Memory | 289 | Feedback from the hippocampal region is assumed to sparsify the pattern. | 2 | ||
| Gluck & Myers; Gateway to Memory | 289 | Under the assumption that the cortex performs competitive learning, strongly activated winning neurons undergo plasticity -- strengthening the weights from active inputs -- while the remaining neurons undergo weight decreases. | 0 | ||
| Gluck & Myers; Gateway to Memory | 290 | One problem and theorizing about hippocampal region function has always been an understanding have very specific activation patterns (e.g. episodic memories) encoded in hippocampus could be transferred to cortical storage. | 1 | ||
| Gluck & Myers; Gateway to Memory | 290 | In Rolls' model, the hippocampus doesn't know where to project information; it simply projects everywhere, and storage occurs automatically wherever conjoint feedforward and feedback projections converge. | 0 | ||
| Gluck & Myers; Gateway to Memory | 290 | Teaching inputs require very specific anatomical properties that appear to exist in only a few places in the brain (e.g. the mossy fiber connections from dentate gyrus to CA3 and climbing fiber inputs to cerebellum). | 0 | ||
| Gluck & Myers; Gateway to Memory | 291 | The Rolls' model requires no more than the ubiquitous Hebbian-like learning in which plasticity occurs to strengthen the connections between any two coactive inputs. | 1 | ||
| Gluck & Myers; Gateway to Memory | 291 | Neurobiological mechanisms for Hebbian learning have been observed in the superficial layers of cerebral cortex. | 0 | ||
| Gluck & Myers; Gateway to Memory | 291 | Subcortical inputs might modulate memory storage for especially significant events. | 0 | ||
| Gluck & Myers; Gateway to Memory | 293 | The cortico-hippocampal model assumes that the entorhinal cortex compresses stimulus representations. | 2 | ||
| Gluck & Myers; Gateway to Memory | 302 | The entorhinal cortex within the hippocampal region has a form intermediate between six-layered neocortex and two-layered allocortex. | 9 | ||
| Gluck & Myers; Gateway to Memory | 302 | Entorhinal cortex receives highly processed, multimodal sensory input and projects to the hippocampus. In turn, hippocampal outputs project to entorhinal cortex and from there back to cortical areas where they arose. | 0 | ||
| Gluck & Myers; Gateway to Memory | 302 | A simple entorhinal model -- clusters of nodes compete to respond to inputs; representations of similar and co-occurring (redundant) inputs are compressed. | 0 | ||
| Gluck & Myers; Gateway to Memory | 302 | Other models have suggested that the entorhinal cortex is involved in stimulus configuration, and the back projections from hippocampus to entorhinal cortex and beyond provide a possible substrate for memory consolidation. | 0 | ||
| Gluck & Myers; Gateway to Memory | 303 | Eichenbaum has suggested that the entorhinal cortex is an intermediate-term buffer, with the ability to configure representations of items that occur with slight temporal displacement. | 1 | ||
| Gluck & Myers; Gateway to Memory | 307 | An excitatory neurotransmitter increases the probability that the postsynaptic neuron will become active, and an inhibitory neurotransmitter decreases this probability. | 4 | ||
| Gluck & Myers; Gateway to Memory | 307 | Whereas neurotransmitters carry messages between neurons, neuromodulators affect how those messages are processed. | 0 | ||
| Gluck & Myers; Gateway to Memory | 308 | Acetylcholine (ACh) and Memory Function | 1 | ||
| Gluck & Myers; Gateway to Memory | 308 | Schematic of some important cholinergic projections in the brain. (diagram) | 0 | ||
| Gluck & Myers; Gateway to Memory | 311 | Many computational models assume that hippocampal field CA3 functions as autoassociator. | 3 | ||
| Gluck & Myers; Gateway to Memory | 311 | In the autoassociator, a pattern of input activations is stored in the CA3 network by strengthening connections between pairs of nodes that are simultaneously active. | 0 | ||
| Gluck & Myers; Gateway to Memory | 311 | When a partial or distorted version of the stored pattern is presented as input to the autoassociator, this activates the corresponding subset of the nodes in the stored pattern, and from these nodes, activity will spread to the remaining nodes, retrieving the rest of the pattern. | 0 | ||
| Gluck & Myers; Gateway to Memory | 315 | When cholinergic input is present, the hippocampus can store new patterns; when ACh is absent, the hippocampus can retrieve patterns that were previously stored. | 4 | ||
| Gluck & Myers; Gateway to Memory | 315 | An assumption is that acetylcholine levels should be high during learning and low thereafter. | 0 | ||
| Gluck & Myers; Gateway to Memory | 315 | New information is stored in the presence of acetylcholine. | 0 | ||
| Gluck & Myers; Gateway to Memory | 317 | Acetylcholine is not needed for recalling information. | 2 | ||
| Gluck & Myers; Gateway to Memory | 318 | When ACh is high, the hippocampus tends to store new information; when ACh is low, the hippocampus tends to retrieve previously stored information. | 1 | ||
| Gluck & Myers; Gateway to Memory | 334 | Cholinergic projection from medial septum to the hippocampus and how it can modulate hippocampal learning rates. | 16 | ||
| Gluck & Myers; Gateway to Memory | 334 | Acetylcholine functions as a neuromodulator in cortex, as well as in the hippocampus. | 0 | ||
| Gluck & Myers; Gateway to Memory | 334 | Dopamine modulation in predicting reward, and norepinephrine in modulating sensitivity to behavioral context. | 0 | ||
| Gluck & Myers; Gateway to Memory | 335 | Theta rhythm, a phenomenon in which large numbers of hippocampal neurons begin to fire in synchronous bursts, approximately 4 to 8 times a second. | 1 | ||
| Gluck & Myers; Gateway to Memory | 335 | Although the firing of any one neuron results in a minuscule electric charge, the synchronized activity of many thousands of neurons causes an electric charge large enough to be detected through the scalp. | 0 | ||
| Gluck & Myers; Gateway to Memory | 335 | In a rat, theta rhythm typically occurs during exploratory behaviors, such as walking, rearing, and sniffing. | 0 | ||
| Gluck & Myers; Gateway to Memory | 335 | Non-synchronized firing occurs during consummatory behaviors, when the animal is sitting quietly and eating, drinking, or grooming. | 0 | ||
| Gluck & Myers; Gateway to Memory | 335 | Theta rhythm (diagram) | 0 | ||
| Gluck & Myers; Gateway to Memory | 336 | Theory proposes that theta rhythm occurs during exploration and other learning behaviors when new information is bombarding the brain and is being temporarily stored in the hippocampus. | 1 | ||
| Gluck & Myers; Gateway to Memory | 336 | Theta rhythm serves the purpose of rhythmically silencing the hippocampus, breaking a steady stream of inputs into manageable 200 ms packets of information. | 0 | ||
| Gluck & Myers; Gateway to Memory | 336 | Once exploration stops, there is time for the brain to "catch its breath" and analyze the information. | 0 | ||
| Gluck & Myers; Gateway to Memory | 337 | If ACh modulates information storage in hippocampus, it might have a similar function in cortex. | 1 | ||
| Gluck & Myers; Gateway to Memory | 338 | Understanding cholinergic modulation of brain function is important with respect to understanding our normal learning and memory occur. | 1 | ||
| Gluck & Myers; Gateway to Memory | 338 | One of the most common sites of cerebral aneurysm is the anterior communicating artery. The resulting syndrome has three basic components: (1) anteriorgrade amnesia, (2) personality changes (such as loss of self-control, unpredictable aggression, or apathy), and (3) confabulation, or the spontaneous production of false memories. | 0 | ||
| Gluck & Myers; Gateway to Memory | 339 | Confabulation should be distinguished from lying; confabulators are genuinely unaware that their memories are inaccurate. | 1 | ||
| Gluck & Myers; Gateway to Memory | 341 | One anatomical hallmark of Alzheimer's disease is the dysfunction and death of basal forebrain neurons, leading to cholinergic depletion throughout the brain. | 2 | ||
| Gluck & Myers; Gateway to Memory | 341 | Other neuromodulators, including dopamine, norepinephrine, and serotonin, are also reduced in Alzheimer's disease, but the cortical cholinergic systems seem to be affected earlier and to a greater extent. | 0 | ||
| Gluck & Myers; Gateway to Memory | 342 | Various neuromodulators, including acetylcholine (ACh), alter how neurons transmit messages, without altering the content of the message. | 1 | ||
| Gluck & Myers; Gateway to Memory | 342 | The major cholinergic input to the hippocampus is the medial septum in the basal forebrain. | 0 | ||
| Gluck & Myers; Gateway to Memory | 345 | The hippocampus interacts with other brain regions that are its partners in learning and memory, including the entorhinal cortex, the basal forebrain, the cerebellum, and the primary sensory and motor cortices. | 3 | ||
| Gluck & Myers; Gateway to Memory | 346 | Individuals would've medial temporal lobe epilepsy generally report memory and paramedics even before surgery, and this is at least partially due to his sclerosis (scarring) and the hippocampus as a result of repeated seizures. | 1 | ||
| Gluck & Myers; Gateway to Memory | 347 | Studies of the simplest forms of animal learning may assist us toward understanding more complex aspects of learning and memory in humans. | 1 | ||
| Gluck & Myers; Gateway to Memory | 350 | Computational models have assisted our understanding of the neural bases of learning and memory. | 3 | ||
| Gluck & Myers; Gateway to Memory | 350 | Covering a range of models from a variety of researchers, makes it possible for different models to capture different aspects of anatomy and physiology and different kinds of behavior, and in many cases these models complement each other. | 0 | ||
| Gluck & Myers; Gateway to Memory | 350 | Informative models should raise as many new questions as they answer old ones. | 0 | ||
| Gluck & Myers; Gateway to Memory | |||||