Abstract
We present a novel visual illusion called "Temporal Fusion". When a visual target, such as a bar stimulus, is flashed twice in succession with an inter-stimulus interval of 100 ms, the two flashes are easily discernible as flicker. We have discovered that these two target flashes are fused perceptually if we present a two-bar mask stimulus that is spatially abutting (not overlapping) the target during the period of time between flashes. Human psychophysical testing on naive observers confirms that the temporal fusion percept is confused with a single long-duration target flash (having an overall duration matching the two flashes in the illusory condition) that is flanked by the mask during its midlife. To determine the neural basis for the illusion we conducted single-cell neurophysiological recordings in area V1 of two awake rhesus monkeys. We confirmed that responses to the temporal fusion illusion closely resemble the responses to the non-illusory long target stimulus that has the same appearance as the illusion. Importantly, the similarity of the responses between the two conditions is specifically strong in the response to the mask’s termination. This emphasizes the perceptual importance of responses to stimulus termination, and suggests that stimulus transients from the mask are not only capable of suppressing target transients (as we have previously found in visual masking), but they also play a role in shaping the perception and visibility of surrounding stimuli.
Meeting abstract presented at VSS 2012