Coding of Episodic Memory in the Human Hippocampus

Department

Neurosurgery; 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

0027-8424

Volume

115

Issue

5

First Page

E1093

Last Page

E1098

Digital Object Identifier (DOI)

10.1073/pnas.1716443115

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