Postural regulation and stability with acoustic input in normal-hearing subjects

BACKGROUND: Postural regulation is based on complex interactions among postural subsystems. The auditory system too appears to have an influence on postural control. OBJECTIVE: The aim of this study was to measure the influence of auditory input on postural control and to gain a deeper understanding of the interactions between auditory input and postural subsystems including subjective aspects. MATERIALS AND METHODS: In 30 healthy normal-hearing subjects, postural regulation and stability was measured with the Interactive Balance System (IBS; Inc. neurodata GmbH, Wien, Österreich) in 8 test positions with noise (frontal presentation) and plugged without noise. The IBS is an electrophysiological measurement device that measures postural control at the product level (e.g., stability, weight distribution) and the mechanisms of postural subsystems at the process level based on frequency-oriented fast-Fourier analysis of force–time relation. RESULTS: At the process level, we found a relevant reduction (η(p)(2) ≥ 0.10) of postural regulation with noise in the frequency bands F1 (visual and nigrostriatal system η(p)(2) = 0.122) and F2–4 (peripheral vestibular system η(p)(2) = 0.125). At the product level, the weight distribution index (WDI) parameter showed a relevant increase with noise (η(p)(2) = 0.159). No difference between the auditory conditions was found for postural stability (parameter: stability indicator, ST). Substantial interindividual variations in the subjective estimation of the influence of auditory inputs on stability were observed. CONCLUSION: In this study, a shift in the activity of postural subsystems was observed with auditory input, while no difference was seen in ST. This leads to new insights into mechanisms of audiovestibular interaction.