title: Parietal cortex mediates conscious perception of illusory gestalt.
abstract: Grouping local elements into a holistic percept, also known as spatial binding, is crucial for meaningful perception. Previous studies have shown that neurons in early visual areas V1 and V2 can signal complex grouping-related information, such as illusory contours or object-border ownerships. However, relatively little is known about higher-level processes contributing to these signals and mediating global Gestalt perception. We used a novel bistable motion illusion that induced alternating and mutually exclusive vivid conscious experiences of either dynamic illusory contours forming a global Gestalt or moving ungrouped local elements while the visual stimulation remained the same. fMRI in healthy human volunteers revealed that activity fluctuations in two sites of the parietal cortex, the superior parietal lobe and the anterior intraparietal sulcus (aIPS), correlated specifically with the perception of the grouped illusory Gestalt as opposed to perception of ungrouped local elements. We then disturbed activity at these two sites in the same participants using transcranial magnetic stimulation (TMS). TMS over aIPS led to a selective shortening of the duration of the global Gestalt percept, with no effect on that of local elements. The results suggest that aIPS activity is directly involved in the process of spatial binding during effortless viewing in the healthy brain. Conscious perception of global Gestalt is therefore associated with aIPS function, similar to attention and perceptual selection.
authors.affiliation: Vision and Cognition Laboratory, Centre for Integrative Neuroscience, University of Tübingen, D-72076 Tübingen, Germany.
authors.forename: Natalia
authors.initials: N
authors.lastname: Zaretskaya
authors.forename: Stuart
authors.initials: S
authors.lastname: Anstis
authors.forename: Andreas
authors.initials: A
authors.lastname: Bartels
mesh_terms: D000328:Adult; D001519:Behavior / Q000502:physiology; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010296:Parietal Lobe / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult