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Hiroaki Gomi, Naotoshi Abekawa, Shin'ya Nishida; Implicit sensorimotor control: Rapid motor responses of arm and eye share the visual motion encoding. Journal of Vision 2005;5(8):363. doi: 10.1167/5.8.363.
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© ARVO (1962-2015); The Authors (2016-present)
Increasing lines of evidence have suggested that arm reaching is under online visuomotor control. We recently found a short latency manual response induced by a large-field visual motion during arm movement, which we named “manual following response (MFR)”. To explore the sensory processing involved in the MFR, we here examined the effect of image contrast and spatiotemporal frequency of sinusoidal grating patterns on the short latency manual response. In the experiment, vertical sinusoidal grating pattern with a particular image contrast was shown on the monitor. Subjects were asked to hit the center of a computer monitor with their index finger with an assistance of beeps for movement timing. The grating pattern started to move either rightward or leftward (randomized) 120 ms after the beginning of the arm movement. The MFR amplitude was quantified by the difference, between the rightward and leftward moving conditions, in the hand velocity averaged over a brief period after the stimulus onset. In the first experiment, the image contrast was changed between blocks. As the image contrast was increased, the MFR amplitude increased, and its latency decreased, up to the image contrast of ∼10 %, and almost leveled off thereafter. In the second experiment, the spatiotemporal frequency of the grating was changed. The MFR amplitude increased as the grating temporal frequency increased, but decreased beyond the peak temporal frequency around 15 – 20 Hz independent to the spatial frequency. For the stimulus < 15 Hz, the MFR amplitude was almost linearly proportional to the log-velocity of the stimulus. Moreover, the spatiotemporal tuning functions, as well as short response latencies, are similar to those of the ocular response induced by a large-field visual motion known as ‘ocular following response’ (OFR). This suggests that MFR and OFR share a common visual motion processing mechanism.
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