Summation between nearby motion signals and facilitative/inhibitory interactions between distant motion signals

To explain the finding that motion assimilation was dominant between nearby motion signals while motion contrast between distant ones, a center-surrou nd antagonistic mechanism was proposed [Nawrot & Sekuler (1990). Vision Res earch, 30, 1439-1451]. However, motion assimilation occurred not only betwe en nearby signals but also between distant ones, suggesting the existence o f a center-surround non-antagonistic mechanism [Ido, Ohtani & Ejima (1997). Vision Research, 37, 1565-1574]. The present study was designed to provide direct evidence for the non-antagonistic mechanism, and to examine further the motion interactions which operate in different spatial scales. The nat ure of motion interaction between the test and the inducer was examined by varying the size, the number of frames, the frame duration and the inter-fr ame displacement of random-dot kinematograms, The results were consistent w ith the notion that there are three types of interactions in human motion p rocessing; one is a summation process effective within nearby regions, and the other two are facilitative and inhibitory induction processes operating over larger spatial scales. Analysis of the results in terms of the Fourie r components suggests that the facilitative and the inhibitory induction pr ocesses may be sensitive, respectively to the lower and the higher temporal frequency components of the stimulus. (C) 2000 Elsevier Science Ltd. All r ights reserved.