Investigating the correlation between sharp wave-ripples and eye movements during memory consolidation and retrieval in the human hippocampus

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

Nasim Mortazavi¹ (nmortaza@uwo.ca), Milad Khaki¹, Ben Corrigan¹, Greydon Gilmore², Jonathan Lau², Ana Suller Marti², Julio Martinez-Trujillo¹; ¹Schulich School of Medicine & Dentistry, Departments of Physiology, Pharmacology and Psychiatry, University of Western Ontario, London, ON, Canada, ²3Department of Clinical Neurological Sciences, London Health Sciences Centre, University of Western Ontario, London, Ontario, Canada

Introduction: Sharp Wave Ripples (SWRs) are transient electrophysiological events originating from the human hippocampus, believed to be crucial for memory encoding, consolidation, and retrieval. The emergence of SWRs has been intensively debated. We explore the relationship between SWRs in the human hippocampus (HPC) and eye movements during an associative memory task within a 3D virtual environment. Hypothesis: We hypothesize that SWRs are linked to saccadic and smooth pursuit eye movements (SPEMs). Method: We employed stereoencephalography (SEEG) signals from epilepsy patients with HPC electrodes and recorded eye positions while participants performed the task. We utilized a robust SWR detection algorithm based on existing research to identify SWRs and applied our lab's algorithm to align SWRs with saccades and SPEMs. Our memory task involves navigating a circular maze with two arms, striking objects whose colour correlates with maze wall textures. A state-space model was used to estimate each participant's dynamic learning curve. Results: Our preliminary results involved three participants with nine electrodes implanted in their hippocampus and 15 channels in the CA1. The study involved 2355 seconds of gameplay, during which 7620 sharp-wave ripple (SWR) events were detected. The SWR rates were found to be significantly higher than the baseline recordings. Additionally, the study implied a temporal correlation between SWRs and eye movements during the task, with 15188 saccades and 2662 SPEMs observed. Conclusion: Our results indicate a link between hippocampal SWRs and eye movements during associative learning, suggesting a role of eye movements in associative memory formation in humans.

Topic Area: LONG-TERM MEMORY: Episodic