Abstract
It is well known that postural stability is enhanced by stable structure in the periphery, whereas optical flow in the periphery can destabilize posture and create vivid perception of self-motion (vection). The question of interest here is whether cognitive processes can influence apparently automatic visual control of posture. Recent studies have found that cognitive tasks can influence postural control, suggesting that mental imagery and visual control of posture involve shared resources. We investigated the effects of two cognitive tasks — the Brooks Letter Task (visuo-spatial) and Speech Shadowing (auditory-semantic) — on the postural stability of participants while they observed the interior of a room, which filled the visual field. The virtual room was stationary in the "Static" condition; the room oscillated slowly (0.1 Hz) toward and away from the observer in the "Moving" condition. Throughout both conditions, participants stood on a transverse bar, which was mounted on a force plate. Dependent measures included stance breaks and fore-aft fluctuations of posture recorded by a force plate. The results showed that stance breaks and fore-aft variations of posture were significantly greater in the Moving as compared with the Static condition. FFT’s confirmed that the differences in postural stability between Static and Moving conditions matched the frequency (0.1 Hz) of the oscillating room. Postural stability during performance of the cognitive tasks was no different than that during a control condition (no cognitive task). Our findings confirm the strong effects of peripheral visual stimulation on posture, and they indicate that this basic function is impervious to concurrent performance of both visual-spatial and auditory-semantic cognitive tasks.
Meeting abstract presented at VSS 2012