Abstract
When a sudden large field visual motion is presented during arm reaching, a quick and involuntary manual response occurs in the direction of visual motion. A unique feature of this manual following response (MFR), distinctive from the ocular following response and possibly from conscious visual motion perception, is high sensitivity to visual motion presented in the far periphery. We recently demonstrated that the MFR amplitude increased progressively with stimulus size (up to 50 deg in diameter) when the stimulus area was filled with the low spatial frequency sinusoidal grating (Gomi et al. 2007 Society for Neurosci.). To evaluate how the central and peripheral visual fields contribute to, and interact in, the MFR generation, we here presented sudden sinusoidal grating motions with different spatial frequencies (0.02, 0.05, 0.2, 0.8 cpd, 10Hz) in one of or combination of the three eccentric visual fields (center, near-periphery, far-periphery) during arm reaching movements. When the stimulus was shown only in the far- or near-periphery, the strong MFR was generated especially by the spatial frequency of 0.05 cpd, suggesting a significant influence of the peripheral visual field on the MFR. More interestingly, when more than two visual fields were stimulated simultaneously, the MFR amplitudes were not simply accumulated. The MFR amplitude was sometimes even smaller than that evoked only one of the visual fields when the adjacent visual fields were simultaneously stimulated. When the center and far-periphery were simultaneously stimulated, on the other hand, the MFR appeared to be greater than the MFR in each of the single visual field conditions. These results suggest that strong suppression interactions exist between the adjacent visual fields in generating MFR, possibly contributed by the spatial integration process of visual motion between the striate and extrastriate cortices.