Mapping the neglect syndrome onto neurofunctional streams

This chapter provides an overview of the syndrome of unilateral spatial neglect (USN) as a multicomponent deficit, focusing on the distinction between its 'perceptual' and 'premotor' impairments, as well as on related evidence from the processing of visual illusions. It compares the USN syndrome, and its neural correlates with the two disorders representing the neuropsychological counterparts of vision-for-perception (the 'ventral' stream), and of vision-for-action (the 'dorsal' stream). From the neuropsychological vantage-point of USN, the chapter takes the view that the two visual streams dichotomy ' both in the original version of Ungerleider and Mishkin (1982), and in the development by Milner and Goodale ' captures only partially the neural loops concerned with perception and action in the visual domain. The syndrome of USN suggests the existence of a neural system supporting perceptual awareness in spatial reference frames, for vision, and for other sensory modalities, as well as goal-directed, intentional action in the space surrounding us. A third, dorsal-ventral, stream, including the inferior parietal lobule, and the ventral premotor cortex, may constitute the neural underpinnings of spatial awareness for perception and action.