Coding of episodic memory in the human hippocampus

John T. Wixted, Stephen Goldinger, Larry R. Squire, Joel R. Kuhn, Megan H. Papesh, Kris A. Smith, David M. Treiman, Peter N. Steinmetz

Research output: Contribution to journalArticle

7 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)E1093-E1098
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number5
StatePublished - Jan 30 2018

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Keywords

  • Amygdala
  • Episodic memory
  • Hippocampus
  • Single units

ASJC Scopus subject areas

  • General

Cite this

Wixted, J. T., Goldinger, S., Squire, L. R., Kuhn, J. R., Papesh, M. H., Smith, K. A., Treiman, D. M., & Steinmetz, P. N. (2018). Coding of episodic memory in the human hippocampus. Proceedings of the National Academy of Sciences of the United States of America, 115(5), E1093-E1098.