Temporal facilitation for moving stimuli is independent of changes in direction

A flash that is presented aligned with a moving stimulus appears to lag beh ind the position of the moving stimulus. This flash-lag phenomenon reflects a processing advantage for moving stimuli (Metzger, W. (1932) Psychologisc he Forschung 16, 176-200; MacKay, D. M. (1958) Nature 181, 507-508; Nijhawa n, R. (1994) Nature 370, 256-257; Purushothaman, G., Patel, S.S., Bedell, H .E., & Ogmen, H. (1998) Nature 396, 424; Whitney, D. & Murakami, I. (1998) Nature Neuroscience 1, 656-657). The present study measures the sensitivity of the illusion to unpredictable changes in the direction of motion. A mov ing stimulus translated upwards and then made a 90 degrees turn leftward or rightward. The flash-lag illusion was measured and it was found that, alth ough the change in direction was unpredictable, the flash was still perceiv ed to lag behind the moving stimulus at all points along the trajectory, a finding that is at odds with the extrapolation hypothesis (Nijhawan, R. (19 94) Nature 370, 256-257). The results suggest that there is a shorter laten cy of the neural response to motion even during unpredictable changes in di rection. The latency facilitation therefore appears to be omnidirectional r ather than specific to a predictable path of motion (Grzywacz, N. M. & Amth or, F. R. (1993) Journal of Neurophysiology 69, 2188-2199). (C) 2000 Elsevi er Science Ltd. All rights reserved.