Experimental Study on Control of Visually Evoked Postural Responses by Galvanic Vestibular Stimulation

Visually evoked postural responses (VEPRs) are physiological responses to perceived motion that are related to visually induced motion sickness (VIMS). We considered that VEPRs are just a conflict correction response aimed at matching information from the senses of vision and equilibrium. We also believe that understanding the consequences of suppression or acceleration of VEPRs may elucidate the pathogenic mechanism of VIMS and help establish methods for preventing VIMS. Our group has developed a system combining digital imagery and galvanic vestibular stimulation (GVS) to manipulate VEPRs. In this study, we attempted to verify a method of extrinsically controlling VEPRs. We determined the GVS current values that induced loss of motion sensation in subjects watching moving objects, measured body sway under different movie speed and GVS-off or on conditions, and tested whether GVS could counteract VEPRs. The results clearly showed that 1) the GVS current value increased along with increased motion speed observed in a video, and 2) it was possible to control VEPRs by GVS. However, it was difficult to completely control VEPRs by GVS, possibly because characteristics of posture can change based on the allocation of consciousness.