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Abstract

Grouping local elements into a holistic percept, also known as spatial binding, is crucial for meaningful perception. Lesions in posterior parts of the brain are known to impair perceptual grouping, but in the healthy brain this process has only been studied indirectly. Here we use a novel bi-stable illusion, which induces alternating and mutually exclusive subjective experiences of either grouped (global) or ungrouped (local) elements, while the visual stimulation remains the same. We show that global perceptual periods are related to stronger brain activity in the parietal cortex and that they are selectively shortened when parietal activity is disturbed by brain stimulation. Our findings thus provide direct evidence that consciously experienced grouping is mediated by parietal function, similar to attention and perceptual selection.