Auditory contributions to maintaining balance.

Maintaining balance relies on integration of inputs from the visual, vestibular, and proprioceptive systems. The auditory system has not been credited with a similar contributory role, despite its ability to provide spatial orienting cues with extreme speed and accuracy. Here, we determined the ability of external auditory signals to reduce postural sway, measured as the root-mean-square velocity of center of pressure of a standing subject, in a series of subjects with varying levels of imbalance standing in the dark. The maximum root-mean-square center of pressure among our subjects decreased from 7.0 cm/sec in silence to 4.7 cm/sec.with the addition of external sound. The addition of sound allowed subjects to decrease sway by 41 percent. The amount of improvement due to sound was 54% of the amount of improvement observed in postural sway when visual cues only were provided to subjects standing in silence. These data support the significant effect of the auditory system in providing balance-related cues and suggest that interventions such as hearing aids or cochlear implants may be useful in improving postural stability and reducing falls.