Abnormal attentional modulation of retinotopic cortex in parietal patients with spatial neglect.
Brain regions beyond visual cortex are thought to be responsible for attention-related modulation of visual processing [1, 2], but most evidence is indirect. Here, we applied functional magnetic resonance imaging (fMRI), including retinotopic mapping of visual areas, to patients with focal right-parietal lesions and left spatial neglect [3, 4]. When attentional load at fixation was minimal, retinotopic areas in right visual cortex showed preserved responses to task-irrelevant checkerboards in the contralateral left hemifield, analogously to left visual cortex for right-hemifield checkerboards, indicating a "symmetric" pattern in both hemispheres with respect to contralateral stimulation under these conditions. But when attentional load at fixation was increased, a functional asymmetry emerged for visual cortex, with contralateral responses in right visual areas being pathologically reduced (even eliminated for right V4/TEO), whereas left visual areas showed no such reduction in their contralateral response. These results reveal attention-dependent abnormalities in visual cortex after lesions in distant (parietal) regions. This may explain otherwise puzzling aspects of neglect [5, 6], as confirmed here by additional behavioral testing.
Laboratory for Neurology and Imaging of Cognition, Department of Neurosciences and Clinical Neurology, University of Geneva, Geneva, Switzerland. patrik.vuilleumier@medecine.unige.ch
Patrik
P
Vuilleumier
Sophie
S
Schwartz
Vincent
V
Verdon
Angelo
A
Maravita
Chloe
C
Hutton
Masud
M
Husain
Jon
J
Driver
D001288:Attention / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D010296:Parietal Lobe / Q000293:injuries*; D010468:Perceptual Disorders / Q000503:physiopathology*; D014793:Visual Cortex / Q000503:physiopathology*