Hippocampal gamma predicts associative memory performance as measured by acute and chronic intracranial EEG

Simon Henin, Anita Shankar, Nicholas Hasulak, Daniel Friedman, Patricia Dugan, Lucia Melloni, Adeen Flinker, Cansu Sarac, May Fang, Werner Doyle, Thomas Tcheng, Orrin Devinsky, Lila Davachi, Anli Liu

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Abstract

Direct recordings from the human brain have historically involved epilepsy patients undergoing invasive electroencephalography (iEEG) for surgery. However, these measurements are temporally limited and affected by clinical variables. The RNS System (NeuroPace, Inc.) is a chronic, closed-loop electrographic seizure detection and stimulation system. When adapted by investigators for research, it facilitates cognitive testing in a controlled ambulatory setting, with measurements collected over months to years. We utilized an associative learning paradigm in 5 patients with traditional iEEG and 3 patients with chronic iEEG, and found increased hippocampal gamma (60–100 Hz) sustained at 1.3–1.5 seconds during encoding in successful versus failed trials in surgical patients, with similar results in our RNS System patients (1.4–1.6 seconds). Our findings replicate other studies demonstrating that sustained hippocampal gamma supports encoding. Importantly, we have validated the RNS System to make sensitive measurements of hippocampal dynamics during cognitive tasks in a chronic ambulatory research setting.

Original languageEnglish (US)
Article number593
JournalScientific reports
Volume9
Issue number1
DOIs
StatePublished - Dec 1 2019

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Henin, S., Shankar, A., Hasulak, N., Friedman, D., Dugan, P., Melloni, L., Flinker, A., Sarac, C., Fang, M., Doyle, W., Tcheng, T., Devinsky, O., Davachi, L., & Liu, A. (2019). Hippocampal gamma predicts associative memory performance as measured by acute and chronic intracranial EEG. Scientific reports, 9(1), [593]. https://doi.org/10.1038/s41598-018-37561-z