title: Tactile awareness and limb position in neglect: functional magnetic resonance imaging.
abstract: We studied a patient with right parietal damage for whom tactile stimuli on the right/ipsilesional hand (projecting to the intact left hemisphere) were extinguished from awareness during double simultaneous stimulation, when his right hand was positioned in the left/contralesional space. This demonstrates the role of an egocentric spatial reference frame in attention that can determine awareness of stimuli despite intact sensory pathways. Using functional magnetic resonance imaging to elucidate the neural correlates of such perceptual extinction, we found that limb position modulated neural responses to tactile stimuli at early cortical stages (SI) in the intact hemisphere. Activity in bilateral middle frontal gyri also was modulated by limb position and may contribute to integrate sensory inputs into a supramodal, egocentric representation of space.
authors.affiliation: Department of Neurology and Neurosciences, University of Geneva, Switzerland.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Valenza
authors.forename: Mohamed L
authors.initials: ML
authors.lastname: Seghier
authors.forename: Sophie
authors.initials: S
authors.lastname: Schwartz
authors.forename: François
authors.initials: F
authors.lastname: Lazeyras
authors.forename: Patrik
authors.initials: P
authors.lastname: Vuilleumier
mesh_terms: D000368:Aged; D001925:Brain Damage, Chronic / Q000209:etiology / Q000503:physiopathology; D001931:Brain Mapping; D005121:Extremities / Q000473:pathology / Q000502:physiology; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010296:Parietal Lobe / Q000473:pathology / Q000503:physiopathology*; D010468:Perceptual Disorders / Q000209:etiology / Q000503:physiopathology*; D011187:Posture / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D020521:Stroke / Q000150:complications / Q000503:physiopathology; D014110:Touch / Q000502:physiology*