Résumé
Movements to body positions, such as clapping or bringing food to the mouth, are completed effortlessly even without visual information about body position. The locations of these positions, also called somatosensory targets, are specified by nonvisual sources from vestibular, proprioceptive, and tactile cues. Disrupting vestibular signals is known to distort perceived body orientation; however, it is unknown whether vestibular perturbations also impair movements toward somatosensory targets. Moreover, it remains uncertain whether concurrent visual feedback of limb position can mitigate any vestibular-related movement errors. The purpose of this research was to explore how vestibular disruption influences reaching to somatosensory targets, and whether providing visual information about body position alters perception during planning.
Participants reached to somatosensory targets (i.e., the nose, and the left and right cheek)—indicated by a brief vibrotactile stimulus. Movements were performed with and without concurrent visual feedback of themselves during movement planning. Bilateral-bipolar galvanic vestibular stimulation (GVS) created the perception of illusory tilt to the left (L-GVS) or right (R-GVS) along the frontal plane. Results revealed that reaching error in the direction-axis were biased based on GVS condition, with significantly greater errors during both L-GVS and R-GVS (p<0.05). Although visual feedback did not affect error, participants had longer reaction times with visual feedback available. These findings suggest that disrupting vestibular input degrades reaching accuracy to somatosensory targets and that visual information, while used during planning, does not compensate for vestibular-induced errors. These findings elucidate the role of vestibular and visual systems when making movements to body positions.
