Effects of auditory feedback on movements with two-segment sequence and eye-hand coordination: using a short auditory contact cue

Abstract During sequential reaches to multiple targets, eye and hand movements are highly coordinated, and the gaze is anchored to each target until the reaching hand makes contact to each of them. Such contact events are monitored by multimodal (visual, proprioceptive) sensory systems, and one function of the gaze anchoring to each target is verification of successful target contact (reach completion). The present study focused on this verification function and examined how planning and control of eye and hand movements during two-segment eye-hand movements are affected by augmented auditory feedback of reach completion. Young adults made a reach to the first target with a saccade, and then made another saccade to the second target in blocked trials. An auditory target-contact cue condition delivered four short sounds during the initial reach, and the last sound was synchronized with target contact, whereas a control condition lacked the last target-contact sound. The results showed that saccadic reaction time increased with the target-contact cue, especially when the reaching accuracy demand was high. The reach also became slower with lower peak velocity and longer time to peak velocity with that cue, suggesting that the limb-motor system lower the preplanned speed of the reach in a top-down fashion for a better preparation toward reach completion. However, no auditory effects were found for the timing of gaze shift to the second target. These results were different from those seen in previous studies, indicating that the effects of the additional auditory contact feedback differ depending on behavioral tasks and cue characteristics.