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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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
Pages (from-to)10503-10508
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number33
StatePublished - 18 Aug 2015


FundersFunder number
National Institute of Mental Health5T32 MH015795, F32 NS50067-03
National Institute of Neurological Disorders and StrokeNS033221
National Institute on Drug Abuse5T90DA022768-02
National Institute of Neurological Disorders and StrokeR56NS033221


    • Discrimination
    • Hippocampus
    • Invariance
    • Memory
    • Selectivity


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