Abstract
Metacontrast is a visual illusion, in which visibility of a briefly presented stimulus (target) is reduced by a spatially adjacent and temporally following brief stimulus (mask). In our previous psychological study in human, the strength of metacontrast changed depending on the relationship of stimulus parameters between the two stimuli and the stimulus-dependency varied with timing of the mask presentation. The suppressive effects of metacontrast would be caused via interactions among visual pathways with different stimulus specificities and temporal properties. In the present study, we recorded V1 neurons of anesthetized cats to explore the neural mechanisms underlying metacontrast. Stationary flashes of sinusoidal grating were used as stimuli. Receptive field was stimulated with circular grating patch (target) and its surround was stimulated with annular grating (mask) with varying stimulus onset asynchrony (SOA)(-120–+120 msec). Orientation and contrast were identical between two stimuli, and spatial frequency (SF) of the mask was varied while that of the target was fixed at the optimal. Predominant effect of the mask was suppression of target responses when the mask was presented with SOAs between 0 and 120 msec. Time course and strength of the suppression were dependent on the relationship of SFs of two stimuli, and the mask with SF same as that of target exhibited the strongest and most prolonged suppression. These results suggest that suppressive response modulation by a stimulation of receptive field surround underlies the perceptual metacontrast. [Jpn J Physiol 55 Suppl:S186 (2005)]
