Auditory biofeedback substitutes for loss of sensory information in maintaining stance

Abstract

The importance of sensory feedback for postural control in stance is evident from the balance improvements occurring when sensory information from the vestibular, somatosensory, and visual systems is available. However, the extent to which also audio-biofeedback (ABF) information can improve balance has not been determined. It is also unknown why additional artificial sensory feedback is more effective for some subjects than others and in some environmental contexts than others. The aim of this study was to determine the relative effectiveness of an ABF system to reduce postural sway in stance in healthy control subjects and in subjects with bilateral vestibular loss, under conditions of reduced vestibular, visual, and somatosensory inputs. This ABF system used a threshold region and non-linear scaling parameters customized for each individual, to provide subjects with pitch and volume coding of their body sway. ABF had the largest effect on reducing the body sway of the subjects with bilateral vestibular loss when the environment provided limited visual and somatosensory information; it had the smallest effect on reducing the sway of subjects with bilateral vestibular loss, when the environment provided full somatosensory information. The extent that all subjects substituted ABF information for their loss of sensory information was related to the extent that each subject was visually dependent or somatosensory-dependent for their postural control. Comparison of postural sway under a variety of sensory conditions suggests that patients with profound bilateral loss of vestibular function show larger than normal information redundancy among the remaining senses and ABF of trunk sway. The results support the hypothesis that the nervous system uses augmented sensory information differently depending both on the environment and on individual proclivities to rely on vestibular, somatosensory or visual information to control sway.

Auditory white noise reduces postural fluctuations even in the absence of vision

“…Hegeman et al (2005) found very small improvements in stability with sound that provided information about position, but only when participants had their eyes open and were standing on a hard surface; they found no effect when participants' eyes were closed, when participants were standing on a foam surface designed to reduce somatosensory feedback from the feet, or when the sound provided velocity information. In contrast, Dozza et al (2007) found a reduction in sway when the sound provided information about position, but only when participants' eyes were closed and participants were standing on a foam surface. They also found a lot of intersubject variability, possibly indicating that participants were responding to the feedback in individualized ways (Dozza et al 2007).…”

“…Successful control relies on prediction and feedback from the somatosensory, vestibular, and visual modalities (Dozza et al 2007). Postural sway is sensitive to subtle changes in feedback (Yeh et al 2010), and increased availability of information from these systems has been shown to improve balance, as in the case of light touch (Jeka et al 1997;Wing et al 2011).…”

“…Although multisensory feedback is essential for postural control, individuals differentially depend on combinations of somatosensory, vestibular, and visual feedback for postural stability. The dominant dependence can change with circumstance, including impairment of one or more of the senses (Dozza et al 2007;Hegeman et al 2005). Partial compensation occurs in these systems to ensure balance not only for major impairment, but also for temporary interruptions, such as when we close our eyes.…”

“…Impairment of vision, proprioception, or vestibular systems leads to more reliance on audition (Dozza et al 2007;Hegeman et al 2005;Palm et al 2009), and hearing loss has been shown to increase variability in postural sway, although the explanation for this is unclear. Juntunen et al (1987) proposed that subclinical damage to the vestibular system with noise-induced hearing loss could explain the effect on stability, but there is no corroboration for vestibular damage in their participants because of the difficulty in examining damage too subtle for current clinical detection.…”

“…Imbalance and hearing loss co-occur in a number of disorders, including Ménière's disease, multiple sclerosis, viral infections, and vestibular schwannoma (Mangiore 2012). Reduction in sway with auditory feedback has also been shown in people without visual, proprioceptive, or vestibular deficits (Dozza et al 2007); audition might be utilized for postural stability even in people without impairment of other perceptual systems.…”