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Global integration of local color differences in transparency perception: An fMRI study

Published online by Cambridge University Press:  06 September 2006

MICHEL DOJAT
Affiliation:
Unité mixte Inserm/UJF U594, Neuroimagerie Fonctionnelle et Métabolique, LRC CEA 30V, Grenoble, France
LOŸS PIETTRE
Affiliation:
Unité mixte Inserm/UJF U594, Neuroimagerie Fonctionnelle et Métabolique, LRC CEA 30V, Grenoble, France
CHANTAL DELON-MARTIN
Affiliation:
Unité mixte Inserm/UJF U594, Neuroimagerie Fonctionnelle et Métabolique, LRC CEA 30V, Grenoble, France
MATHILDE PACHOT-CLOUARD
Affiliation:
Unité mixte Inserm/UJF U594, Neuroimagerie Fonctionnelle et Métabolique, LRC CEA 30V, Grenoble, France
CHRISTOPH SEGEBARTH
Affiliation:
Unité mixte Inserm/UJF U594, Neuroimagerie Fonctionnelle et Métabolique, LRC CEA 30V, Grenoble, France
KENNETH KNOBLAUCH
Affiliation:
Inserm, U371, Cerveau et Vision, Department of Cognitive Neurosciences, Bron, France

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.

Information

Type
SURFACE COLOR PERCEPTION
Copyright
© 2006 Cambridge University Press

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