Hemodynamic imaging data have provided evidence of a functional and neuroanatomical segregation between dorsal and ventral streams of the brain devoted to visual spatial and nonspatial feature processing, with no indications of the timing of their differential activation. Furthermore, neuropsychological findings showed a dissociation between symptoms reported by patients with damage to the occipito-parietal cortex (WHERE system), resulting in spatial hemineglect and problems in movement perception, and those reported by patients with damage to the occipito-temporal cortex (WHAT system), showing color blindness or deficits in segregating figures from backgrounds and in recognizing human faces. In this regard, studies in split-brain patients have also shown a right hemispheric dominance for spatial orienting of attention, and a right-sided bilateral control of visual space. Aim of the present study was to investigate neural mechanisms subserving spatial and nonspatial attentional mechanisms by recording event-related brain potentials (ERPs) in right-handed, young, healthy volunteers. The relations between the two attentional mechanisms were systematically investigated by adopting distinct experimental paradigms in which spatial selection independent of object identity (Exp.1), object selection independent of spatial coordinates (Exp. 2), conjoined object and space selection (object selection in a given spatial location Exp. 3) were separately involved. The time course and topographical distribution of major ERP components reflecting different processing stages were analyzed. Experimental findings support the view of different mechanisms for space and object attentional processing whose activation would occur independently from each other (Exp. 1 and Exp. 2) or in parallel, but not independently (Exp.3), as a function of task demands. Topographic ERP mapping showed hemispheric asymmetries and a neurofunctional segregation of object and space attentional systems at an early sensory level.
Electrophysiological indexes of visual attention mechanisms for spatial and non-spatial features
Zani A
2000
Abstract
Hemodynamic imaging data have provided evidence of a functional and neuroanatomical segregation between dorsal and ventral streams of the brain devoted to visual spatial and nonspatial feature processing, with no indications of the timing of their differential activation. Furthermore, neuropsychological findings showed a dissociation between symptoms reported by patients with damage to the occipito-parietal cortex (WHERE system), resulting in spatial hemineglect and problems in movement perception, and those reported by patients with damage to the occipito-temporal cortex (WHAT system), showing color blindness or deficits in segregating figures from backgrounds and in recognizing human faces. In this regard, studies in split-brain patients have also shown a right hemispheric dominance for spatial orienting of attention, and a right-sided bilateral control of visual space. Aim of the present study was to investigate neural mechanisms subserving spatial and nonspatial attentional mechanisms by recording event-related brain potentials (ERPs) in right-handed, young, healthy volunteers. The relations between the two attentional mechanisms were systematically investigated by adopting distinct experimental paradigms in which spatial selection independent of object identity (Exp.1), object selection independent of spatial coordinates (Exp. 2), conjoined object and space selection (object selection in a given spatial location Exp. 3) were separately involved. The time course and topographical distribution of major ERP components reflecting different processing stages were analyzed. Experimental findings support the view of different mechanisms for space and object attentional processing whose activation would occur independently from each other (Exp. 1 and Exp. 2) or in parallel, but not independently (Exp.3), as a function of task demands. Topographic ERP mapping showed hemispheric asymmetries and a neurofunctional segregation of object and space attentional systems at an early sensory level.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
