Extrapersonal visual unilateral spatial neglect and its neuroanatomy

The neural correlates of left extrapersonal visual unilateral spatial neglect (VUSN), the more extensively investigated component of the neglect syndrome, are reviewed. Damage to a number of right-hemisphere regions brings about VUSN: the posterior parietal cortex (inferior parietal lobule) and, although less frequently, the premotor cortex and subcortical structures, such as the thalamus and the basal ganglia, and white matter fiber tracts. In recent years, a number of studies have investigated the possible association of specific components of left VUSN with damage to specific brain regions within the right hemisphere. The putative distinction most extensively investigated from an anatomical perspective concerns the perceptual vs premotor components of VUSN. In addition, a fine-grain componential analysis of the behavioral tasks used to investigate VUSN is providing more specific insight into the pathological mechanisms underlying the variety of its manifestations. The emerging pattern is that USN is a multifarious disorder, in which specific deficits are associated with damage localized in discrete brain regions and neural circuits. These data concur with evidence from other domains (functional neuroimaging, neurophysiology) to suggest a highly multicomponential neural and functional architecture of spatial cognition.