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Abstract:
The paradigm of monocular rivalry (MR), also called pattern rivalry, has been used to illustrate selective suppression of one of two superimposed visual patterns or images. Much like the related phenomenon of binocular rivalry (BR), perception during MR is dynamic, and often marked by dominance of only one of the competing patterns, with complete invisibility of its rival. However, MR distinguishes itself from its counterpart in that it arises in the absence of any interocular conflict, but is highly restricted in the types of stimuli that will engage in spontaneous alternation. Here we report several experiments that attempt to identify the principles by which perception selects and/or suppresses superimposed patterns during MR. Stimuli generally consisted of superimposed orthogonal gratings, which have been shown previously to engage in vigorous rivalry. However, in the present study, some of the patterns were complete, covering the extent of the stimulus, while other patterns were 'partial', covering only a portion of the stimulus (eg containing a blank window). Superimposing complete and partial stimuli provided a heterogeneous MR stimulus, with some regions containing pattern conflict and others containing only one pattern. We report that, upon viewing these stimuli, perceptual dominance of a partial pattern often entailed the complete suppression of its rival, even in those regions (up to several degrees in size) devoid of local competition. These results illustrate that, in resolving perceptual conflict, the brain dissects a superimposed stimulus according to inferences regarding the global structure of the competing patterns. Additional experiments revealed similar results with complete and partial competing patterns during BR.
