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Sketchpad Series

Uncovering the neural basis for two path integration homing tasks: Triangle Completion and Loop Closure

Poster Session B - Sunday, March 30, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

Alina S. Tu¹ (alinat2@uci.edu), Michael J. Starrett Ambrose¹, Marie Karpinska², Mary Hegarty², Elizabeth R. Chrastil¹; ¹University of California, Irvine, ²University of California, Santa Barbara

Path integration, the ability to continuously update one’s position and orientation in space using self-motion cues, is fundamental to navigation. This ability is assessed through homing tasks like Triangle Completion and Loop Closure. In Triangle Completion, participants estimate the direction and distance back to the starting point after walking two legs of a triangle. Loop Closure involves participants identifying when they have returned to the starting point while walking in a circle. Surprisingly, preliminary findings from 194 participants revealed weak correlations between these tasks. Moreover, self-reported strategies showed task-specific differences: in Loop Closure, continuously updating the trajectory to the start location—a homing-vector strategy—was more effective, whereas in Triangle Completion, summing path segments to locate the start—a configural strategy—yielded better results. To explore these differences, we examined the neural basis of path integration, focusing on the entorhinal cortex (EC), which contains grid cells that fire to create a metric grid for environmental mapping. 69 participants completed both homing tasks in walking, immersive virtual reality before completing another path integration task while undergoing fMRI scanning to measure grid-cell-like representations in EC. Given the configural-strategy advantage in Loop, we hypothesized grid-cell-like signals would correlate more with Loop performance than Triangle, supporting the use of metric information for configural strategies. Alternatively, if EC activity supports configural strategies regardless of homing accuracy, it may correlate more with Triangle, where configural strategies were more common. By examining the neural contributions to these path integration tasks, this study advances our understanding of the cognitive processes supporting navigation.

Topic Area: LONG-TERM MEMORY: Other