Non-retinotopic adaptive center-surround modulation in motion processing.

The early visual system is organized retinotopically. However, under ecological viewing conditions, motion perception occurs in non-retinotopic coordinates. Even though many studies revealed the central role of non-retinotopic processes, very little is known about their mechanisms and neural correlates. Tadin and colleagues found that increasing the spatial size of a high-contrast drifting-Gabor deteriorates motion-direction discrimination, whereas the opposite occurs with a low-contrast stimulus. The results were proposed to reflect an adaptive center-surround antagonism, whereby at low-contrast the excitatory center dominates whereas at high-contrast suppressive-surround mechanisms become more effective. Because ecological vision is non-retinotopic, we tested the hypothesis that the non-retinotopic system also processes motion information by means of an adaptive center-surround mechanism. We used the Ternus-Pikler display designed to provide either a retinotopic or a non-retinotopic reference-frame. Our results suggest that the non-retinotopic processes underlying motion perception are also mediated by an adaptive center-surround mechanism.