Age-related changes in updating gaze position – an eye movement analogue of path integration

Path integration (PI) is a navigation process that allows an organism to update its current location in reference to a starting point. PI computations 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. If a PI-like process is apparent in eye movements, it should decline with aging, as it does with whole-body movements. Here, we created an eyetracking version of a PI task and investigated the influence of aging on eye movement-based PI. 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 use. However, when participants could be cued to any enroute location during a block, and thus memory for the entire route was required, processing times increased, accuracy decreased, and overt revisits to enroute locations increased with the number of locations in a route, indicative of configural updating. Whereas older participants showed similar patterns of strategy use as younger participants, their performance indicates that the resulting internal representations differed in their accuracy and manner of use. The findings from the present study suggest that spatial tracking and updating mechanisms are generalizable across effector systems.