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Abstract:
Asynchronous presentation of two dissimilar patterns at the same point in visual space can lead to the perceptual domination of the second pattern, accompanied by suppression of the first. This flash suppression is particularly pronounced when there is direct interocular conflict, as in binocular rivalry flash suppression (BRFS, Wolfe, 1984), or more subtle interocular differences as in generalized flash suppression (GFS, Wilke et al, 2003). Under conditions favorable to monocular rivalry, asynchronous presentation is also effective at promoting exclusive visibility when two overlapping patterns are shown to corresponding portions of the same eye (Maier et al., ECVP 2004). The dynamics of all these phenomena appear to be closely related, all possessing an increasing probability of perceptual suppression with longer ‘adaptation’ intervals before the presentation of the second stimulus.
Here we present neuronal activity in monkey areas V4 and MT during BRFS using various pre-flash intervals. Animals performed a fixation task while dichoptic grating patterns were presented asynchronously to the two eyes. Pre-flash intervals were varied over the range used for psychophysical testing. We found that neural responses to this presentation followed the expectations based on perception, with longer pre-flash intervals eliciting larger modulation. This was largely caused by an inhibitory response component that could only be evoked if pre-flash intervals were large enough to reliably elicit perceptual suppression. This time course of perception-related modulation was largely comparable to that observed with GFS in an accompanying study. Taken together, these observations provide evidence that the diverse phenomena of flash suppression share common active mechanisms related not to any particular stimulation condition, but more generally to perceptual organization.
