Visual Influence on Postural Reactions to Sudden Antero-posterior Support Surface Movements

Abstract

Visual influence on force reactions to sudden antero-posterior (AP) translations of the support surface in 10 healthy men 23-58 years old (mean 36 years) were studied. Displacements ranged between 13 and 127 mm in both backwards and forwards directions. the experiment was conducted using a modified EquiTest dynamic posturography apparatus. An interactive menu-driven software enabled selection of a suitable translation pattern (i.e. square wave) in the AP direction. Data from four vertical force transducers were acquired and the position of centre of pressure (CP) in the AP direction was computed as function of time. the movement of CP in response to AP translation was characterized by the amplitude of the maximum CP displacement relative to the platform and the latency until maximum CP displacement occurred. the experiment unveiled that the latency to maximum CP displacement was larger for conditions with vision present. Furthermore, both the amplitude and latency to maximum CP deflection were increasing functions of translation amplitude. It is proposed that visual feedback influences the neural control on the postural reactions to sudden support surface translations. Absence of visual cues seems to cause a more rapid correction of the body position.

Key Words:

• postural control
• dynamic posturography
• visual feedback
• perturbation