A novel stimulation protocol for vestibular rehabilitation

Vestibular hypofunction due to aging or disease can be severely debilitating for daily life, causing dizziness, space disorientation, imbalance, limited mobility, and increased risk of falls. Current methods and techniques for vestibular rehabilitation often fail short of achieving stable, effective results due to the lack of physiologically-based, ergonomic approaches. Here we propose a novel approach based on the application of small-amplitude random displacements of the head and body, which can lead to enhanced vestibular function. The phenomenon we studied is akin to stochastic resonance, whereby the application of a given, optimal level of noise during periodic or non-periodic stimuli can determine an increased sensitivity in nonlinear systems, such as the vestibular perceptual system. The idea is that an appropriate level of noise can raise subthreshold stimuli above threshold, thereby making them detectable by the brain. We tested the protocol in a series of experiments involving 30 healthy young participants who were asked to discriminate the direction of whole-body motion imparted by a MOOG platform. Blindfolded subjects were presented with the discrimination of forward-backward single-cycle sinusoidal motion in a two-alternative forced-choice paradigm. The procedure followed an adaptive staircase. Vestibular threshold (i.e., minimum amplitude of applied motion that was discriminated by the subjects) was then computed from the slope of the psychometric function fitting the individual performance. We compared the vestibular threshold between the baseline condition (no external noise) and the conditions when band-limited white-noise was applied by the platform in the forward-backward direction. We found that in 26/30 participants the discrimination threshold was better with at least one noise level than that at baseline. The overall response curve roughly obeyed the bell-shaped function typical of stochastic resonance. We conclude that small-amplitude noise can ameliorate vestibular perception even in healthy young subjects. The advantage of this approach is that it is non-invasive and ecological, since it involves the application of small oscillations to the patient. Moreover, the task is easily understood since it consists of a classical discrimination paradigm.