The role of an auditory cue in generating anticipatory postural adjustments in response to an external perturbation.

Anticipatory postural adjustments (APAs) are usually generated to minimize the potential postural disturbance induced by predictable external perturbations. Visual information about a perturbation is important for the generation of APAs, but whether people can rely on auditory information to generate APAs is unknown. The aim of this study was to investigate the role of an auditory cue in generating APAs when visual information is not available. Fifteen young adults participated in the study. They received external perturbations a) with visual information but no auditory information available, b) without neither visual nor auditory information, c) with both visual and auditory information available, and d) with only auditory information available. Electromyography (EMG) activities of eight leg and trunk muscles and displacements of the center-of-pressure (COP) were recorded and analyzed during the anticipatory and compensatory (CPAs) phases. Outcome measures included the latencies and integrals of muscle activities, COP displacements, and indices of co-contraction and reciprocal activation of muscles. The results showed that after a short training, participants were able to rely only on the auditory cue to generate APAs comparable to that when the visual information was available. In addition, a training effect was found such that the participants demonstrated stronger APAs and less demands for CPAs through the training trials. The outcome provides a foundation for future studies focusing on the utilization of auditory cues for postural control in older adults and individuals who have vision deficit.