David Jessop, Laurent Bouyer, McFadyen BJ

Vestibulo-visual integration for postural stability during standing

Presented at International Symposium on Posture and Gait, Bologna, Italy, July 2009; Submitted to J. Neurophysiology

Abstract: The aim of the present study was to identify the contributions of integrated visual and vestibular information on postural control during standing using binaural-bipolar galvanic vestibular stimulation (GVS) and optokinetic stimulation (OS) in the form of a rightward rotating cluster field. Two visual conditions (unperturbed vision, nO; optokinetic stimulation, OS) were combined with 3 vestibular conditions (no stimulation, nG, GVS right, GR; GVS left, GL). The six conditions, therefore, were: no sensory stimulation (nG_nO), independent sensory stimulations (nG_OS, GR_nO and GL_nO) and combined sensory stimulations (GR_OS and GL_OS). Head and trunk lateral angular movement (roll) and lateral displacement of center of pressure were evaluated. Our data show a postural deviation toward the anode side for the head, trunk and CoP for the independent GVS stimulations. The OS also caused comparable lateral displacements of the head and trunk towards the right, but the displacement of the CoP was not different from quiet standing. A mathematical summation of individual mean displacements for NS_OS and GR_UV was comparable to results of the combined stimulations for the same directions. Furthermore, a mathematical summation of NS_OS and GL_UV results was similar to the opposing GL_OS combined stimulations as well as to NS_UV. These results demonstrate that visual and vestibular stimulations appear to differ with respect to lower body responses and that individual vestibular and visual information initially sum in a linear fashion before some information processing mechanisms may take over.