Bischof, W. F. and Di Lollo, V., V. (1996). Psychophysical evidence for sustained input to directionally-selective motion mechanisms. Perception, 25, 65-76.
We report human psychophysical evidence congruent with neurophysiological findings of a susteined input to directionally-selective motion sensors in cat visual cortex. Apparent motion was produced by displaying a group of dots in two frames (F1 and F2), where F2 was a translated version of F1. All stimulus sequences included a period during which F1 and F2 were displayed concurrently (combined images) and a period during which only F1 or F2 was on display (single images). There were three stimulus sequences: display beginning with combined and ending with single image (0-SOA), display beginning with single and ending with combined image (0-STA), and display beginning with F1, continuing with combined image, and ending with F2 (ASYN). The sequences are illustrated in Figure 1. Six durations of single and of combined images (10, 20, 40, 80, 160, or 320 ms) were crossed factorially in each stimulus sequence. Direction motion was seen easily at long durations of the single image in all stimulus sequences, as would be expected on the basis of sustained input to the directional motion-sensing mechanisms. Perception of directional motion improved with the duration of single images, but declined as the duration of combined images was increased. Baker and Cynader's (1994) model could account for the effect of duration of single images, but not for the effect of duration of combined images. An elaborated version of the model provides a good qualitative match to all empirical findings.
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