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Abstract:
Perception of surface orientation is an essential step for
the reconstruction of the 3D structure of an object. Human lesion
and functional neuroimaging studies have demonstrated the
importance of the parietal lobe in this task. In primate single
unit studies, neurons in the caudal part of the intraparietal
sulcus (CIP) were found to be active during the extraction of
surface orientation through monocular (2D) cues such as texture
gradients and linear perspective as well as binocular (3D) cues
such as disparity gradient and orientation disparity. We used event
related fMRI to study the functional neuroanatomy of surface
orientation discrimination using stimuli with monocular depth cues
in six volunteers. Both posterior (CIP) and anterior (AIP) areas
within the intraparietal sulcus (IPS) showed a stronger activation
during surface orientation as compared to a control (colour
discrimination) task using identical stimuli. Furthermore, the
signal changes in CIP showed a greater performance effect than
those in AIP, suggesting that CIP is tightly linked to the
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