Sensitivity to Illusory Target Motion in Elderly and Association with Problems in the Activities of Daily Life

Abstract

A horizontally moving background makes a downward moving disc appear to move in the opposite direction of the background. Using a large touch screen and a disc interception task, we showed that healthy older adults (OA) are more influenced by this illusion than younger adults (YA). This is possibly related to a reduced ability to ignore irrelevant sensory information, and thus to sensory integration. Sensory integration is crucial to perform the activities of daily living (ADLs). Therefore, the tapping test could help diagnose sensory integration issues and predict future ADLs problems in OA. We examined whether initial lab results could be replicated using a mobile version of the test on a tablet and whether issues in ADLs are associated with stronger effects of the illusion. Nineteen healthy YA and twenty-four OA with a range of ADLs difficulties were tested (fifteen considered as fit OA and nine considered as unfit because they could not perform all the conditions of the experiment). The illusion effect was replicated for YA but was smaller in fit OA compared to YA. This discrepancy increased when proprioceptive or cognitive dual tasks were performed. These results might be explained by the fact that OA tend to hit in the middle of the tablet regardless of the direction of motion of the disc and the background. Unfit OA showed a reverse illusion effect compared to YA (in the direction of being 'dragged' by the background rather than in the direction of illusory target motion). The failure to fully replicate the lab results may be due to increased task difficulty. Nevertheless, correlations were found between various aspects of tapping performance and participants' scores in ADLs tests, which suggest that the mobile interception test may be useful as a diagnostic test of ADLs issues.

Meeting abstract presented at VSS 2018