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Processing of Shape from Coherent Motion in the Human Visual Cortex

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http://pubman.mpdl.mpg.de/cone/persons/resource/persons83781

Altmann,  CF
Department Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons84023

Kourtzi,  Z
Department Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics, Max Planck Society;
Department Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Max Planck Society;

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Citation

Altmann, C., & Kourtzi, Z. (2004). Processing of Shape from Coherent Motion in the Human Visual Cortex. Poster presented at 7th Tübingen Perception Conference (TWK 2004), Tübingen, Germany.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0013-DA03-E
Abstract
Interactions in our dynamic environment require that the visual system processes both the shape and motion of objects. Different cortical areas have been proposed to be involved in the processing of visual motion (hMT+/V5 = human middle temporal homologue), kinetic boundaries (KO = kinetic occipital) and object shape (LOC = lateral occipital complex). The goal of this study was to investigate whether these areas are involved in the perception of shapes dened by motion coherence. To this end, we used human event-related fMRI and employed stimuli in which the shape was dened by the relative motion of random dots in the shape and the background. We manipulated the perception of these shapes by independently varying the motion coherence of the dots in the shape and the background. Increased motion coherence in either the shape or the background improved the behavioral performance of the observers in a shape categorization task. FMRI responses in the LOC and KO were consistent with the behavioral performance; that is, enhanced fMRI responses were observed with increased motion coherence in either the shape or the background. Interestingly, hMT+/V5 showed activation patterns similar to the LOC, suggesting strong interactions between ventral (LOC) and dorsal (hMT+/V5) visual areas in the perception of shape from motion. To further investigate shape representations from motion in the different visual areas we tested for selectivity for shape and motion direction information. To this end, we used an fMRI adaptation paradigm in which lower fMRI responses are observed for two identical than two different stimuli presented consecutively in a trial. Recovery from adaptation was observed across changes in shape in the LOC, KO, and hMT+/V5, but not in early visual areas. In a third study, we tested whether shape and motion related areas are selective for the 3D structure of shapes. To this end, we employed an fMRI adaptation paradigm and similar stimuli as in the two previous studies. In addition, these stimuli were rendered with 3D structure using horizontal disparity cues. Recovery from adaptation was observed across changes in 3D structure in the LOC, KO, and hMT+/V5. In summary, these ndings suggest that not only object (LOC) but also motionrelated areas (hMT+/V5) are involved in the selective representation and perception of shapes dened by coherent motion.