Neural evidence for recognition of naturalistic videos in monkey hippocampus

John J. Sakon, Wendy A. Suzuki

Research output: Contribution to journalArticlepeer-review


The role of the hippocampus in recognition memory has long been a source of debate. Tasks used to study recognition that typically require an explicit probe, where the participant must make a response to prove they remember, yield mixed results on hippocampal involvement. Here, we tasked monkeys to freely view naturalistic videos, and only tested their memory via looking times for two separate novel versus repeat video conditions on each trial. Notably, a large proportion (>30%) of hippocampal neurons differentiated these videos via changes in firing rates time-locked to the duration of their presentation on screen, and not during the delay period between them as would be expected for working memory. Many of these single neurons (>15%) contributed to both retrieval conditions, and differentiated novel from repeat videos across trials with trial-unique content, suggesting they detect familiarity. The majority of neurons contributing to the classifier showed an enhancement in firing rate on repeat compared with novel videos, a pattern which has not previously been shown in hippocampus. These results suggest the hippocampus contributes to recognition memory via familiarity during free-viewing.

Original languageEnglish (US)
Pages (from-to)916-932
Number of pages17
Issue number8
StatePublished - Aug 2021


  • hippocampus
  • monkey
  • recognition memory
  • single units
  • videos

ASJC Scopus subject areas

  • Cognitive Neuroscience


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