Environment geometry alters sequential route learning and its integration into cognitive maps

Researchers hypothesize that geometric irregularities can impede spatial memory by distorting neural metrics of space provided by entorhinal grid cells. However, irregularly-shaped geometries could also contribute orientation information that benefits spatial memory. Moreover, serial order effects could counteract or amplify geometry effects during route navigation. Our study directly tests how effects of environment geometry (trapezoid and square) and series in route navigation interact to influence spatial memory in a virtual navigation task. We uncover effects of environment geometry predicted by grid cell models and serial order effects predicted by path integration models. Critically, our results demonstrate that these effects combine in an additive manner, such that location memory toward the end of a route in regions with the largest geometric irregularities (trapezoid) yield the worst spatial memory. Additionally, self-report measures of navigational ability are associated with increased sensitivity to geometric irregularities, emphasizing the essential role of individual differences in navigation.