AVAILABILITY OF VISUAL AND PROPRIOCEPTIVE AFFERENT MESSAGES AND POSTURAL CONTROL IN ELDERLY ADULTS

The ability of young and elderly adults to keep a stable upright postu re while facing changes in the availability of visual and/or propriomu scular information was investigated. The two sensory sources of inform ation were alternatively available and withdrawn, jointly and separate ly, during 10-s alternating sequences. Vision was modified by means of liquid-crystal goggles, and proprioception was altered by means of te ndon vibration of both antagonistic ankle muscles. Elderly adults were less stable than young adults when vision was withdrawn. Both groups were greatly affected when propriomuscular inputs were altered by vibr ation. Under constant visual conditions and following a propriomuscula r perturbation (i.e., vibration), elderly adults were unable to take a dvantage of the reinsertion of propriomuscular inputs. They showed a t ransient, decreased stability and were unable to fully recover during a 10-s period, whereas young adults were able to rapidly integrate the information to stabilize their posture. When both propriomuscular and visual inputs were withdrawn and concurrently reinserted, the elderly adults did not show a transitory increase in the velocity of the cent er of foot pressure. The present results extend findings on the inabil ity of elderly adults to reconfigure rapidly the postural set followin g reinsertion of sensory inputs. The results also suggest that elderly adults have difficulties in taking advantage of sensory redundancy in postural control.