Aging and selective sensorimotor strategies in the regulation of upright balance

The effects of aging and repeated exposures on the capability of the center nervous system (CNS) to select pertinent sensory information and resolve sensory conflicts were investigated with virtual reality. Healthy young and older adults maintained quiet stance while immersed in a virtual environment (VE) for 1 hour during which transient visual and/or surface perturbations were randomly presented. Visual perturbations were induced by sudden pitch or roll plane tilts of the VE viewed through a helmet-mounted display, and combined with or without surface perturbations presented in a direction that was either identical or opposite to the visual perturbations. Results showed a profound influence of aging on postural adjustments measured by EMG responses and displacements of the center of pressure (COP) and body's center of mass (COM) in the recovery of upright stance, especially in the presence of sensory conflicts. Older adults relied more on vision as compared to young adults. Aging affects the interaction of the somatosensory and visual systems on the control of equilibrium during standing and the ability of CNS to resolve sensory conflicts. However, even with a one-hour immersion in virtual environment and exposure to sensory conflicts, it is possible for the CNS to recalibrate and adapt to the changes, while improving balance capability in older adults. Thus, preventive and rehabilitation programs targeting postural control in older adults should take into account the possible impairment of sensory organization or sensorimotor integration and include VE training under conditions of sensory conflicts.