Two cortical systems for reaching in central and peripheral vision.
Parietal lesions in humans can produce a specific disruption of visually guided hand movement, termed optic ataxia. The fact that the deficit mainly occurs in peripheral vision suggests that reaching in foveal and extrafoveal vision rely on two different neural substrates. In the present study, we have directly tested this hypothesis by event-related fMRI in healthy subjects. Brain activity was measured when participants reached toward central or peripheral visual targets. Our results confirm the existence of two systems, differently modulated by the two conditions. Reaching in central vision involved a restricted network including the medial intraparietal sulcus (mIPS) and the caudal part of the dorsal premotor cortex (PMd). Reaching in peripheral vision activated in addition the parieto-occipital junction (POJ) and a more rostral part of PMd. These results show that reaching to the peripheral visual field engages a more extensive cortical network than reaching to the central visual field.
Prado
Jérôme
J
INSERM U371, Cerveau et Vision, Department of Cognitive Neurosciences, 69675 Bron Cedex, France. jprado@isc.cnrs.fr
Clavagnier
Simon
S
Otzenberger
Hélène
H
Scheiber
Christian
C
Kennedy
Henry
H
Perenin
Marie-Thérèse
MT
D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D005260:Female; D006225:Hand; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009778:Occipital Lobe / Q000502:physiology; D010296:Parietal Lobe / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*