Cerebral Cortex Advance Access published online on March 28, 2004
Cerebral Cortex, doi:10.1093/cercor/bhh040
© 2004 by Oxford University Press
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1 Laboratorium voor Neuro- en Psychofysiologie, K.U. Leuven, Medical School, Herestraat 49, B3000 Leuven, Belgium; Laboratory of Theoretical Neurobiology, Born-Bunge Foundation, University of Antwerp (U.A.), Universiteitsplein 1, B2610 Antwerp, Belgium
* To whom correspondence should be addressed. E-mail: guy.orban{at}med.kuleuven.ac.be.
We used positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) in human subjects to investigate whether the ventral and dorsal visual stream cooperate when active judgements about color have to be made. Color was used as the attribute, because it is processed primarily in the ventral stream. The centrally positioned stimuli were equiluminant shades of brown. The successive color discrimination task was contrasted to a dimming detection task, in which retinal input was identical but with double the number of motor responses. The stimulus presentation rate was parametrically varied and a constant performance level was obtained for all conditions. The visual activation sites were identified by retinotopic mapping and cortical flattening. In addition, one psycho-physical and two fMRI experiments were performed to control for differences in visuospatial attention and motor output. Successive color discrimination involved early visual areas, including V1 and VP and the ventral color-responsive region, as well as anterior and middle dorsal intraparietal sulcus, dorsal premotor cortex and pre-SMA. Cortical regions involved in dimming detection and motor output included area V3A, hMT/V5+, lateral occipital sulcus, posterior dorsal intraparietal sulcus, primary motor cortex and SMA. These experiments demonstrated that even with color as the attribute, successive discrimination, in which a decision process has to link visual signals to motor responses, involves both ventral and dorsal visual stream areas. Key Words:
decision, featural attention, functional imaging, human, parietal cortex, tonic/phasic modulation
Article
Color Discrimination Involves Ventral and Dorsal Stream Visual Areas
2 PET Center, Department of Nuclear Medicine, UZ Gasthuisberg, Herestraat 49, B3000 Leuven, Belgium
3 Laboratorium voor Neuro- en Psychofysiologie, K.U. Leuven, Medical School, Herestraat 49, B3000 Leuven, Belgium
4 MR Research Center, Department of Radiology, UZ Gasthuisberg, Herestraat 49, B3000 Leuven, Belgium
5 Laboratory of Theoretical Neurobiology, Born-Bunge Foundation, University of Antwerp (U.A.), Universiteitsplein 1, B2610 Antwerp, Belgium
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