Concurrent vestibular activation and postural training recalibrate somatosensory, vestibular and gaze stabilization processes.

ABSTRACT

Postural instability is a common symptom of vestibular dysfunction that impacts a person's day-to-day activities. Vestibular rehabilitation is effective in decreasing dizziness, visual symptoms and improving postural control through several mechanisms including sensory reweighting of the vestibular, visual and somatosensory systems. As part of the sensory reweighting mechanisms, vestibular activation exercises with headshaking influence vestibular-ocular reflex (VOR). However, combining challenging vestibular and postural tasks to facilitate more effective rehabilitation outcomes is under-utilized. Understanding how and why this may work is unknown. The aim of the study was to assess sensory reweighting of postural control processing and VOR after concurrent vestibular activation and weight shift training (WST) in healthy young adults. Forty-two participants (18-35years) were randomly assigned into four groups No training/control (CTL), a novel visual feedback WST coupled with a concurrent, rhythmic active horizontal or vertical headshake activity (HHS and VHS), or the same WST with no headshake (NHS). Training was performed for five days. All groups performed baseline- and post-assessments using the video head impulse test, sensory organization test, force platform rotations and electro-oculography. Significantly decreased horizontal eye movement variability in the HHS group compared to the other groups suggests improved gaze stabilization (p = .024). Significantly decreased horizontal VOR gain (p = .040) and somatosensory downweighting (p = .050) were found in the combined headshake groups (HHS and VHS) compared to the other two groups (NHS and CTL). The training also showed a significantly faster automatic postural response (p = .003) with improved flexibility (p = .010) in the headshake groups. The concurrent training influences oculomotor function and suggests improved gaze stabilization through vestibular recalibration due to adaptation and possibly habituation. The novel protocol could be modified into progressive functional activities that would incorporate gaze stabilization exercises. The findings may have implications for future development of vestibular rehabilitation protocols.