Integrating behavioral and physiological models of hippocampal function

Gluck, Mark A.; Myers, Catherine E.

doi:10.1002/(sici)1098-1063(1996)6:6<643::aid-hipo7>3.0.co;2-h

Cited by 18 publications

(12 citation statements)

References 68 publications

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“…Raaijmakers & Shi¡rin 1981) and between the stored record and the`header' by which it is referenced (Morton et al 1985). Other approaches to generating event codes have included using an e¤cient compression of the event representations (Gluck & Myers 1996) and endogenously generated temporally varying codes (Levy 1996). One idea to which we will return is that the hippocampal role in episodic memory might relate to the provision of the spatio-temporal context of the event (O'Keefe & Nadel 1978).…”

Section: A Generic Hippocampo-neocortical Model Of Long-term Memorymentioning

confidence: 99%

Memory for events and their spatial context: models and experiments

Burgess

Becker

King

et al. 2001

Phil. Trans. R. Soc. Lond. B

310

214

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The computational role of the hippocampus in memory has been characterized as: (i) an index to disparate neocortical storage sites; (ii) a time-limited store supporting neocortical long-term memory; and (iii) a content-addressable associative memory. These ideas are reviewed and related to several general aspects of episodic memory, including the di¡erences between episodic, recognition and semantic memory, and whether hippocampal lesions di¡erentially a¡ect recent or remote memories. Some outstanding questions remain, such as: what characterizes episodic retrieval as opposed to other forms of read-out from memory; what triggers the storage of an event memory; and what are the neural mechanisms involved? To address these questions a neural-level model of the medial temporal and parietal roles in retrieval of the spatial context of an event is presented. This model combines the idea that retrieval of the rich context of real-life events is a central characteristic of episodic memory, and the idea that medial temporal allocentric representations are used in long-term storage while parietal egocentric representations are used to imagine, manipulate and re-experience the products of retrieval. The model is consistent with the known neural representation of spatial information in the brain, and provides an explanation for the involvement of Papez's circuit in both the representation of heading direction and in the recollection of episodic information. Two experiments relating to the model are brie£y described. A functional neuroimaging study of memory for the spatial context of life-like events in virtual reality provides support for the model's functional localization. A neuropsychological experiment suggests that the hippocampus does store an allocentric representation of spatial locations.

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Section: A Generic Hippocampo-neocortical Model Of Long-term Memorymentioning

confidence: 99%

Memory for events and their spatial context: models and experiments

Burgess

Becker

King

et al. 2001

Phil. Trans. R. Soc. Lond. B

310

214

View full text Add to dashboard Cite

show abstract

“…Models could also incorporate multiple forms of neurotransmission such as GABAergic and acetylcholinergic systems, which control modes of oscillatory firing in the hippocampus during learning and memory consolidation (Buzsaki, 2001;Hasselmo et al, 2002). Simulations measuring the effects of independently variable rates of apoptosis vs neurogenesis should also be considered in the context of models accounting for cortical-hippocampal cooperation in the retention and retrieval of long-term memory (McClelland et al, 1995;Eichenbaum, 2000;Nadel et al, 2000), spatial memory (McNaughton et al, 1996;Burgess et al, 1998), temporal sequencing (Agster et al, 2002), classical conditioning, and novelty encoding (Gluck and Myers, 1996;Schmajuk et al, 2000).…”

Section: Future Directions In Network Modelingmentioning

confidence: 99%

Simulated Apoptosis/Neurogenesis Regulates Learning and Memory Capabilities of Adaptive Neural Networks

Chambers

Potenza

Hoffman

et al. 2003

Neuropsychopharmacol

140

107

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Characterization of neuronal death and neurogenesis in the adult brain of birds, humans, and other mammals raises the possibility that neuronal turnover represents a special form of neuroplasticity associated with stress responses, cognition, and the pathophysiology and treatment of psychiatric disorders. Multilayer neural network models capable of learning alphabetic character representations via incremental synaptic connection strength changes were used to assess additional learning and memory effects incurred by simulation of coordinated apoptotic and neurogenic events in the middle layer. Using a consistent incremental learning capability across all neurons and experimental conditions, increasing the number of middle layer neurons undergoing turnover increased network learning capacity for new information, and increased forgetting of old information. Simulations also showed that specific patterns of neural turnover based on individual neuronal connection characteristics, or the temporal-spatial pattern of neurons chosen for turnover during new learning impacts new learning performance. These simulations predict that apoptotic and neurogenic events could act together to produce specific learning and memory effects beyond those provided by ongoing mechanisms of connection plasticity in neuronal populations. Regulation of rates as well as patterns of neuronal turnover may serve an important function in tuning the informatic properties of plastic networks according to novel informational demands. Analogous regulation in the hippocampus may provide for adaptive cognitive and emotional responses to novel and stressful contexts, or operate suboptimally as a basis for psychiatric disorders. The implications of these elementary simulations for future biological and neural modeling research on apoptosis and neurogenesis are discussed.

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“…This assumption, in light of available in vivo evidence, led us to hypothesize that ongoing rates of neuronal turnover might be tuned to optimize future network learning according to the degree of novelty inherent to new contextual information presented to the learning system. The plausibility of this idea was reinforced by additional lines of evidence implicating the hippocampus in novelty recognition and encoding (Schmajuk, 2002;Gluck & Myers, 1996), where rates of neurogenesis may correlate with different behavioral responses to environmental novelty (Lemaire, Aurousseau, Le Moal, & Abrous, 1999). Thus, cortiocosteroids and other neural mediators of neurogenic regulation might be evoked with amplitudes or durations in proportion to the degree of stressfully novel environmental contextual change, appropriately preparing hippocampal networks for future learning demands of differential informational burdens.…”

Section: Introductionmentioning

confidence: 99%

Network Modeling of Adult Neurogenesis: Shifting Rates of Neuronal Turnover Optimally Gears Network Learning according to Novelty Gradient

Chambers

Conroy

2007

Journal of Cognitive Neuroscience

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Apoptotic and neurogenic events in the adult hippocampus are hypothesized to play a role in cognitive responses to new contexts. Corticosteroid-mediated stress responses and other neural processes invoked by substantially novel contextual changes may regulate these processes. Using elementary three-layer neural networks that learn by incremental synaptic plasticity, we explored whether the cognitive effects of differential regimens of neuronal turnover depend on the environmental context in terms of the degree of novelty in the new information to be learned. In "adult" networks that had achieved mature synaptic connectivity upon prior learning of the Roman alphabet, imposition of apoptosis/neurogenesis before learning increasingly novel information (alternate Roman < Russian < Hebrew) reveals optimality of informatic cost benefits when rates of turnover are geared in proportion to the degree of novelty. These findings predict that flexible control of rates of apoptosis-neurogenesis within plastic, mature neural systems optimizes learning attributes under varying degrees of contextual change, and that failures in this regulation may define a role for adult hippocampal neurogenesis in novelty- and stress-responsive psychiatric disorders.

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Integrating behavioral and physiological models of hippocampal function

Cited by 18 publications

References 68 publications

Memory for events and their spatial context: models and experiments

Memory for events and their spatial context: models and experiments

Simulated Apoptosis/Neurogenesis Regulates Learning and Memory Capabilities of Adaptive Neural Networks

Network Modeling of Adult Neurogenesis: Shifting Rates of Neuronal Turnover Optimally Gears Network Learning according to Novelty Gradient

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