Title

Coding of Episodic Memory in the Human Hippocampus

Department

neurology

Document Type

Article

Abstract

Neurocomputational models have long posited that episodic memories in the human hippocampus are represented by sparse, stimulus-specific neural codes. A concomitant proposal is that when sparse-distributed neural assemblies become active, they suppress the activity of competing neurons (neural sharpening). We investigated episodic memory coding in the hippocampus and amygdala by measuring single-neuron responses from 20 epilepsy patients (12 female) undergoing intracranial monitoring while they completed a continuous recognition memory task. In the left hippocampus, the distribution of single-neuron activity indicated that only a small fraction of neurons exhibited strong responding to a given repeated word and that each repeated word elicited strong responding in a different small fraction of neurons. This finding reflects sparse distributed coding. The remaining large fraction of neurons exhibited a concurrent reduction in firing rates relative to novel words. The observed pattern accords with longstanding predictions that have previously received scant support from single-cell recordings from human hippocampus.

Medical Subject Headings

neurology

Publication Date

2018

Publication Title

Proceedings of the National Academy of Sciences of the United States of America

ISSN

278424

Volume

115

Issue

5

First Page

E1093

Last Page

E1098

Digital Object Identifier (DOI)

10.1073/pnas.1716443115

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