title: Global integration of local color differences in transparency perception: An fMRI study.
abstract: In normal viewing, the visual system effortlessly assigns approximately constant attributes of color and shape to perceived objects. A fundamental component of this process is the compensation for illuminant variations and intervening media to recover reflectance properties of natural surfaces. We exploited the phenomenon of transparency perception to explore the cortical regions implicated in such processes, using fMRI. By manipulating the coherence of local color differences around a region in an image, we interfered with their global perceptual integration and thereby modified whether the region appeared transparent or not. We found the major cortical activation due to global integration of local color differences to be in the anterior part of the parahippocampal gyrus. Regions differentially activated by chromatic versus achromatic geometric patterns showed no significant differential response related to the coherence/incoherence of local color differences. The results link the integration of local color differences in the extraction of a transparent layer with sites activated by object-related properties of an image.
authors.affiliation: Unité mixte Inserm/UJF U594, Neuroimagerie Fonctionnelle et Métabolique, LRC CEA 30V, Grenoble, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Dojat
authors.forename: Loÿs
authors.initials: L
authors.lastname: Piettre
authors.forename: Chantal
authors.initials: C
authors.lastname: Delon-Martin
authors.forename: Mathilde
authors.initials: M
authors.lastname: Pachot-Clouard
authors.forename: Christoph
authors.initials: C
authors.lastname: Segebarth
authors.forename: Kenneth
authors.initials: K
authors.lastname: Knoblauch
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology; D001921:Brain / Q000033:anatomy & histology / Q000098:blood supply* / Q000502:physiology; D001931:Brain Mapping; D003116:Color; D003118:Color Perception / Q000502:physiology*; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods
chemical_list: D010100:Oxygen