Specific responses of human hippocampal neurons are associated with better memory

Nanthia A. Suthana, Neelroop N. Parikshak, Arne D. Ekstrom, Matias J. Ison, Barbara J. Knowlton, Susan Y. Bookheimer, Itzhak Fried

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

A population of human hippocampal neurons has shown responses to individual concepts (e.g., Jennifer Aniston) that generalize to different instances of the concept. However, recordings from the rodent hippocampus suggest an important function of these neurons is their ability to discriminate overlapping representations, or pattern separate, a process that may facilitate discrimination of similar events for successful memory. In the current study, we explored whether human hippocampal neurons can also demonstrate the ability to discriminate between overlapping representations and whether this selectivity could be directly related to memory performance. We show that among medial temporal lobe (MTL) neurons, certain populations of neurons are selective for a previously studied (target) image in that they show a significant decrease in firing rate to very similar (lure) images. We found that a greater proportion of these neurons can be found in the hippocampus compared with other MTL regions, and that memory for individual items is correlated to the degree of selectivity of hippocampal neurons responsive to those items. Moreover, a greater proportion of hippocampal neurons showed selective firing for target images in good compared with poor performers, with overall memory performance correlated with hippocampal selectivity. In contrast, selectivity in other MTL regions was not associated with memory performance. These findings show that a substantial proportion of human hippocampal neurons encode specific memories that support the discrimination of overlapping representations. These results also provide previously unidentified evidence consistent with a unique role of the human hippocampus in orthogonalization of representations in declarative memory.

Original languageEnglish (US)
Pages (from-to)10503-10508
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number33
DOIs
StatePublished - Aug 18 2015
Externally publishedYes

Keywords

  • Discrimination
  • Hippocampus
  • Invariance
  • Memory
  • Selectivity

ASJC Scopus subject areas

  • General

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