Gamma oscillations during episodic memory processing provide evidence for functional specialization in the longitudinal axis of the human hippocampus

Jui-Jui Lin, Gray Umbach, Michael D. Rugg, Bradley Lega

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


The question of whether the anterior and posterior hippocampus serve different or complementary functional roles during episodic memory processing has been motivated by noteworthy findings in rodent experiments and from noninvasive studies in humans. Researchers have synthesized these data to postulate several models of functional specialization, However, the issue has not been explored in detail using direct brain recordings. We recently published evidence that theta power increases during episodic memory encoding occur in the posterior hippocampus in humans. In our current investigation we analyzed an expanded data set of 32 epilepsy patients undergoing stereo EEG seizure mapping surgery with electrodes precisely targeted to the anterior and posterior hippocampus simultaneously who performed an episodic memory task. Using a repeated measures design, we looked for an interaction between encoding versus retrieval differences in gamma oscillatory power and anterior versus posterior hippocampal location. Our findings are consistent with a recently articulated model (the HERNET model) favoring posterior hippocampal activation during retrieval related processing. We also tested for encoding versus retrieval differences in the preferred gamma frequency band (high versus low gamma oscillations) motivated by published rodent data.
Original languageEnglish
Pages (from-to)68-72
Number of pages5
Issue number2
Early online date5 Nov 2018
Publication statusPublished - Feb 2019
Externally publishedYes


  • episodic memory
  • gamma oscillations
  • hippocampus

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