Sparse and distributed coding of episodic memory in neurons of the human hippocampus.

TitleSparse and distributed coding of episodic memory in neurons of the human hippocampus.
Publication TypeJournal Article
Year of Publication2014
AuthorsWixted JT, Squire LR, Jang Y, Papesh MH, Goldinger SD, Kuhn JR, Smith KA, Treiman DM, Steinmetz PN
JournalProc Natl Acad Sci U S A
Date Published2014 Jul 1
KeywordsEpilepsy, Hippocampus, Humans, Memory, Episodic, Models, Neurological, Neurophysiological Monitoring, Neuropsychological Tests

Neurocomputational models hold that sparse distributed coding is the most efficient way for hippocampal neurons to encode episodic memories rapidly. We investigated the representation of episodic memory in hippocampal neurons of nine epilepsy patients undergoing intracranial monitoring as they discriminated between recently studied words (targets) and new words (foils) on a recognition test. On average, single units and multiunits exhibited higher spike counts in response to targets relative to foils, and the size of this effect correlated with behavioral performance. Further analyses of the spike-count distributions revealed that (i) a small percentage of recorded neurons responded to any one target and (ii) a small percentage of targets elicited a strong response in any one neuron. These findings are consistent with the idea that in the human hippocampus episodic memory is supported by a sparse distributed neural code.

Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID24979802
PubMed Central IDPMC4084456
Grant List1R21DC009781 / DC / NIDCD NIH HHS / United States
NIMH 24600 / / PHS HHS / United States
R01 HD075800 / HD / NICHD NIH HHS / United States
IRG Funded