Two systems in the detection of visual motion.
Several groups of authors have suggested separate mechanisms for the detection of motion and for the detection of pattern characteristics of the same stimuli [Kulikowski, J. J. and Tolhurst, D. J. (1973) J. Physiol., Lond. 232, 149-163; and King-Smith, P. E. (1978) In Armington, J. C., Krauskopf, J. and Wooten, B. R. (Eds) Visual Psychophysics and Physiology. Academic Press, New York]. Their stimuli were generally in the frequency domain. Bonnet [(1975) Psychologia 18, 35-50; (1977) Perception 6, 491-500; and (1982) In Wertheim, A. H., Wagenaar, W. A. and Leibowitz, H. W. (Eds) Tutorials in Motion Perception. Plenum, London] has developed a conceptual model of motion detection in the space-time domain. Two systems are assumed: a movement-analysing system (MAS) which processes the motion phase of any translation and a displacement-analysing system (DAS) which processes the successive stationary components of the stimulus. These proposed mechanisms are studied in experiments which use three different modes of translation of a single spot: continuous, discrete and stop-go-stop. The first mode should preferentially trigger the MAS, the second mode the DAS, while the stop-go-stop mode is a test mode. The results show that for short exposure times (less than or equal to 180 ms) the velocity thresholds for the continuous mode are greater than for the other two modes. For these durations, thresholds of the continuous mode are not lowered by the availability of stationary reference points. The effects of luminance on the results with the three modes support the basic model.
D006801:Humans; D008029:Lighting; D008954:Models, Biological; D009039:Motion Perception; D013997:Time Factors; D014796:Visual Perception