Spatial updating in amnesia using an eye movement analog of path integration

Poster Session B - Sunday, April 14, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Anisha Khosla^1,2 (anisha.khosla@mail.utoronto.ca), Morris Moscovitch^1,2, Jennifer D. Ryan^1,2; ¹University of Toronto, ²Rotman Research Institute, Baycrest

Path integration (PI) allows organisms to navigate home by updating their location in reference to the route’s starting point. The entorhinal cortex (ERC), involved in PI, is modulated similarly by whole-body and eye movements. We previously demonstrated a PI-like process in eye movements using an eyetracking version of commonly used PI tasks. While looking at a computer screen, participants’ eyes were guided by onsets of visual targets, presented one-by-one, at different locations on the screen; following presentation of the last target, participants returned their gaze to the starting point. Akin to whole-body PI, younger and older adults either continuously updated gaze position with respect to the starting location, or maintained an internal map, computing the path only when required. Older adults showed reduced accuracy and more trials with gaze revisits to enroute location(s), indicative of more map-based updating strategies. As the medial temporal lobe (MTL), encompassing the ERC, is implicated in updating self-position via whole-body PI, we investigated its role in updating gaze position. Two amnesic cases, DA and BL, were tested on our eyetracking PI-analog task. DA's more extensive damage includes the ERC, whereas BL’s hippocampal damage is confined to the dentate gyrus. DA and BL had comparable accuracy relative to neurologically intact controls, but DA showed a notable lack of gaze revisits to enroute locations when returning to the start location. These findings suggest that despite MTL damage, updating gaze positions remains feasible, albeit with potential alterations in the information maintained and/or the manner of execution.

Topic Area: LONG-TERM MEMORY: Episodic