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Jing Chen, Matteo Valsecchi, Karl Gegenfurtner; A tight coupling between finger and oculomotor commands. Journal of Vision 2016;16(12):375. doi: https://doi.org/10.1167/16.12.375.
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When human observers track the movements of their own hand with gaze, the eyes can start moving before the finger (i.e., anticipatory smooth pursuit). This anticipation could be the result of a strict coupling between finger and eye motor programming or simply result from a higher-level decision-based predictive signal associated with self-initiated movements. For the present study, we built a mechanic device which could move a visual target either in the same direction of the subjects' hand or towards the opposite direction in different blocks. Observers (N = 12) moved their finger, which was not visible, to either the left or right and back, and were asked to track the visual target with their gaze. The movement length before turning back was on average 19.2 deg (i.e., 10.1 cm; ranging from 15.5 to 22.8 deg). The speed of the finger movement was 26.8 deg/s on average (ranging from 19.6 to 36.6). Congruent pursuit showed stronger anticipation compared to opposite pursuit, as evidenced by decreased pursuit latency (-55 vs -34 ms, respectively), increased lead of the eye to target in positions (0.64 vs 0.41 deg, in the [0 400] ms window after finger onset), decreased saccade rate (0.60 vs 0.71 per second, in the [0 400] ms window), and decreased delay at reversal (10 vs 18 ms). Although some degree of anticipation is occurring for incongruent pursuit, indicating that there is a role for higher-level movement prediction in pursuit anticipation, the fact that anticipation is improved when target and finger move towards the same direction suggests that there is also a direct coupling between finger and eye motor commands.
Meeting abstract presented at VSS 2016
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