Repeated Exposure to Optic Flow in Virtual Reality Induces Changes in Postural Control in Older Adults

This study investigates the effect of repeated exposure to optic flow in virtual reality (VR) on postural control in upright standing in older adults. Eighteen participants (>60 years) completed pre/post assessments consisting of quiet standing in a real environment (eyes open/closed), postural responses to simulated forward and backward self-motion in VR, and proprioceptive perturbations induced by bilateral Achilles and tibialis anterior tendon vibration. Intra- (within similar sensory modality) and inter-modal correlations (within different sensory modalities inducing similar directional postural response) were also investigated to provide insight into sensory integration strategies. The intervention consisted of six 100-s VR bouts alternating simulated forward and backward self-motion. Postural outcomes were quantified from force platform recordings as center of pressure (CoP) velocity and excursion. Repeated VR exposure reduced CoP velocity during simulated forward and backward self-motion (p < 0.05). After the intervention, CoP velocity decreased when standing with eyes closed (p < 0.05) but not when eyes were open. Postural response to tendon vibration was not modified by the intervention (p > 0.05). After the intervention, intra-modal correlation for postural responses to optic flow appeared, whereas a pre-existing inter-modal association between Achilles vibration and forward optic flow disappeared. These results indicate that the postural control system remains adaptable in older adults and highlight the potential of VR environments to improve balance in older adults.