Spatial updating of gaze position in younger and older adults - A path integration-like process in eye movements.

Path integration (PI) is a navigation process that allows an organism to update its current location in reference to a starting point. PI can involve updating self-position continuously with respect to the starting point (continuous updating) or creating a map representation of the route which is then used to compute the homing vector (configural updating). One of the brain areas involved in PI, the entorhinal cortex, is modulated similarly by whole-body and eye movements, suggesting that if PI updates self-position, an analogous process may be used to update gaze position, and may undergo age-related changes. Here, we created an eyetracking version of a PI task in which younger and older participants followed routes with their eyes as guided by visual onsets; at the end of each route, participants were cued to return to the starting point or another enroute location. When only memory for the starting location was required for successful task performance, younger and older adults were generally not influenced by the number of locations, indicative of continuous updating. However, when participants could be cued to any enroute location, thereby requiring memory for the entire route, processing times increased, accuracy decreased, and overt revisits to enroute locations increased with the number of locations in a route, indicative of configural updating. Older participants showed evidence for similar updating strategies as younger participants, but they were less accurate and made more overt revisits to mid-route locations. These findings suggest that spatial updating mechanisms are generalizable across effector systems.