Dataset Information

Heteroassociative storage of hippocampal pattern sequences in the CA3 subregion.

ABSTRACT: Background:Recent research suggests that the CA3 subregion of the hippocampus has properties of both autoassociative network, due to its ability to complete partial cues, tolerate noise, and store associations between memories, and heteroassociative one, due to its ability to store and retrieve sequences of patterns. Although there are several computational models of the CA3 as an autoassociative network, more detailed evaluations of its heteroassociative properties are missing. Methods:We developed a model of the CA3 subregion containing 10,000 integrate-and-fire neurons with both recurrent excitatory and inhibitory connections, and which exhibits coupled oscillations in the gamma and theta ranges. We stored thousands of pattern sequences using a heteroassociative learning rule with competitive synaptic scaling. Results:We showed that a purely heteroassociative network model can (i) retrieve pattern sequences from partial cues with external noise and incomplete connectivity, (ii) achieve homeostasis regarding the number of connections per neuron when many patterns are stored when using synaptic scaling, (iii) continuously update the set of retrievable patterns, guaranteeing that the last stored patterns can be retrieved and older ones can be forgotten. Discussion:Heteroassociative networks with synaptic scaling rules seem sufficient to achieve many desirable features regarding connectivity homeostasis, pattern sequence retrieval, noise tolerance and updating of the set of retrievable patterns.

SUBMITTER: de Camargo RY

PROVIDER: S-EPMC5755486 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Heteroassociative storage of hippocampal pattern sequences in the CA3 subregion.

de Camargo Raphael Y RY Recio Renan S RS Reyes Marcelo B MB

PeerJ 20180102

<h4>Background</h4>Recent research suggests that the CA3 subregion of the hippocampus has properties of both autoassociative network, due to its ability to complete partial cues, tolerate noise, and store associations between memories, and heteroassociative one, due to its ability to store and retrieve sequences of patterns. Although there are several computational models of the CA3 as an autoassociative network, more detailed evaluations of its heteroassociative properties are missing.<h4>Metho ...[more]

PMID: 29312826

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Project description:Age-related cognitive impairments are associated with differentially expressed genes (DEGs) linked to defined neural systems; however, studies examining multiple regions of the hippocampus fail to find links between behavior and transcription in the dentate gyrus (DG). We hypothesized that use of a task requiring intact DG function would emphasize molecular signals in the DG associated with a decline in performance. We used a water maze beacon discrimination task to characterize young and middle-age male F344 rats, followed by a spatial reference memory probe trial test. Middle-age rats showed increased variability in discriminating two identical beacons. Use of an allocentric strategy and formation of a spatial reference memory were not different between age groups; however, older animals compensated for impaired beacon discrimination through greater reliance on spatial reference memory. mRNA sequencing of hippocampal subregions indicated DEGs in the DG of middle-age rats, linked to synaptic function and neurogenesis, correlated with beacon discrimination performance, suggesting that senescence of the DG underlies the impairment. Few genes correlated with spatial memory across age groups, with a greater number in region CA1. Age-related CA1 DEGs, correlated with spatial memory, were linked to regulation of neural activity. These results indicate that the beacon task is sensitive to impairment in middle age, and distinct gene profiles are observed in neural circuits that underlie beacon discrimination performance and allocentric memory. The use of different strategies in older animals and associated transcriptional profiles could provide an animal model for examining cognitive reserve and neural compensation of aging.SIGNIFICANCE STATEMENT Hippocampal subregions are thought to differentially contribute to memory. We took advantage of age-related variability in performance on a water maze beacon task and next-generation sequencing to test the hypothesis that aging of the dentate gyrus is linked to impaired beacon discrimination and compensatory use of allocentric memory. The dentate gyrus expressed synaptic function and neurogenesis genes correlated with beacon discrimination in middle-age animals. Spatial reference memory was associated with CA1 transcriptional correlates linked to regulation of neural activity and use of an allocentric strategy. This is the first study examining transcriptomes of multiple hippocampal subregions to link age-related impairments associated with discrimination of feature overlap and alternate response strategies to gene expression in specific hippocampal subregions.

Dataset Information

Heteroassociative storage of hippocampal pattern sequences in the CA3 subregion.

Publications

Heteroassociative storage of hippocampal pattern sequences in the CA3 subregion.

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