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Vestibular contributions to target-directed reaching movements Brunke, Kirstin Marie

Abstract

Through the use of galvanic vestibular stimulation (GVS), vestibular input has been implicated in the online control of goal-directed actions. Deviations of hand trajectory towards the anode electrode have been observed when stimulation is delivered during movement (Bresciani et al., 2002a; Bresciani et al., 2002b; Mars et al., 2003). The purpose of this experiment was to investigate the role of vestibular information in the planning and execution of target-directed reaching movements. Ten participants sat in a chair fixed to a rotating platform and pointed to an illuminated target when an auditory tone sounded. On all trials, participants were moved from an initial reclined position to a final upright posture and vision of the scene was removed at the auditory tone. Target position could either be cued or uncued. On stimulation trials, a 2 mA, 1000 ms pulse of bipolar, binaural GVS was delivered at the start of the reaction time (RT) interval. Pointing movements were analyzed at the start of the movement, the time of target plane acquisition, and the trial end. Neither GVS nor cue type had an influence on initial pointing direction. At the target plane, anode left trajectories were significantly above and to the left of the no GVS and the anode right trajectories. By trial end, however, clear lateral deviations were present with anode left and anode right trajectories significantly to the left and to the right of the no GVS condition, respectively. These findings suggest that GVS may have little impact on action planning when there is a high degree of whole-body stability. On the other hand, once sufficient time has passed for online control processes to mediate the ongoing action, and a movement transition is imminent, there is an increased weighting of vestibular input.

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