Abstract
Two-stroke apparent movement was first reported at ECVP last year - repeated presentation of a two-frame pattern displacement followed by a brief inter-stimulus interval (ISI) can create an impression of continuous forward motion. The illusion is based on previous reports of reversed apparent motion in two-frame stimuli containing a brief ISI, and can be explained by a biphasic temporal impulse response preceding motion energy detection (Shioiri & Cavanagh, Vision Research, 30, 757–768, 1990; Strout, Pantle & Mills, Vision Research, 34, 3223–3240, 1994; Takeuchi & De Valois, Vision Research, 37, 745–755, 1997).
Two-stroke apparent motion of a sine-wave grating was used as an adapting stimulus in a motion after-effect (MAE) experiment. Naive subjects reported clear MAEs following a short period of adaptation, consistent with unidirectional activation of motion energy sensors. Experiments measured the effect of spatial frequency and ISI duration. MAE duration was longest for ISI durations of 30–40 msec, consistent with earlier research on two-frame apparent motion.