Subsecond dynamics of behaviorally-relevant pattern separation in the human hippocampus

Poster Session D - Monday, April 15, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC
Also presenting in Data Blitz Session 1 - Saturday, April 13, 2024, 1:00 – 2:30 pm EDT, Ballroom East.

Haoxin Zhang¹ (haoxinz1@uci.edu), Ivan Skelin², Shiting Ma¹, Michael Yassa¹, Jack Lin³; ¹University of California Irvine, ²Toronto Western Hospital, ³University of California Davis

Episodic memory depends on pattern separation, the ability to discriminate between unique experiences. The neural dynamics of pattern separation were studied in the rodent hippocampus, with unclear behavioral relevance. Human imaging studies were consistent with behaviorally-relevant pattern separation, but the temporal resolution precluded testing the dynamical theories postulated by the rodent and theoretical work. We recorded the intracranial electroencephalogram (iEEG) from the human temporal lobe (amygdala, dentate gyrus/Cornu Ammonis3 (CA3), CA1 and parahippocampal cortex), during the performance on a mnemonic discrimination task. The stronger hippocampal representational similarity between the previously encoded and newly presented stimulus interferes with correct discrimination. The hippocampal representational dynamics are consistent with discrete attractors, characterized by abrupt transitions at sub-second time scale. Finally, higher dimensionality increase predicts correct discrimination, suggesting the orthoganization as a mechanism implementing the pattern separation. This is the first demonstration of behaviorally-relevant pattern separation dynamics at subsecond timescale in the human brain.

Topic Area: LONG-TERM MEMORY: Episodic