Neuronal mechanisms of saccade-coordinated visuospatial memory in the human brain

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

Qian Chu^1,2,3,4 (qian.chu@mail.utoronto.ca), Thomas M. Biba^2,3, Ivan Skelin³, Suneil K. Kalia^1,2,3, Taufik A. Valiante^1,2,3, Lucia A. Melloni^1,4,5; ¹Max Planck - University of Toronto Centre for Neural Science and Technology, ²University of Toronto, ³Krembil Brain Institute & KITE Research Institute & CRANIA, University Health Network, ⁴Max Planck Institute for Empirical Aesthetics, ⁵New York University

Eye movements and visuospatial memory constantly interact to shape an efficient representation of the world. The behavioral and neurophysiological effects of eye movements on holistic scene memory have been extensively demonstrated, yet it remains elusive how visual identity representations dynamically unfold in active vision. It is known that some neurons in the human medial temporal lobe exhibit highly selective tuning to abstract concepts. We thus leveraged the unique opportunity to record single-unit activity from epilepsy patients and probed the response of identity neurons during visual exploration in different memory stages. We designed a novel gaze-contingent visuospatial memory task, where patients encoded images in a spatial layout with the presentation of images triggered by saccades to cued locations. They subsequently re-explored the layout in the same gaze-contingent manner and were then tasked with judging visuospatial match/mismatch, constituting the retrieval condition. We hypothesized that, during retrieval, identity neurons would fire before the onset of their preferred image and saccade initiation. This anticipatory firing would reflect the learned association between image identity and planned saccade landing location. We found preliminary evidence that identity neurons increased their firing rate before image onset, selectively during retrieval but not encoding. Given the gaze-contingent design, the observed phenomenon cannot be explained by peripheral visual afference and/or receptive field remapping. Our data suggests that visual identity representations are reactivated prior to foveal processing. The findings hint at a novel mechanism for memory-guided eye movements which may underlie the functional enhancement of memory retrieval brought by gaze reinstatement.

Topic Area: PERCEPTION & ACTION: Vision