Attention and spatial cognition: Neural and anatomical substrates of visual neglect

Unilateral spatial neglect (USN) is a neurological disorder often observed following damage to the right cerebral hemisphere. Patients with USN are no longer able to take into account stimuli presented on the left side of space. In this article, we will discuss the neuroanatomical correlates that underlie visuospatial attention and can cause USN, an area of growing research interest in the past 20 years. This syndrome has often been related to cortical damage, notably in the inferior parietal lobule. Other data have also implicated lesions in the inferior frontal gyrus or the superior temporal gyrus. In this article, we will highlight the relevance of viewing USN as a disconnection syndrome of interconnected cerebral areas, as opposed to a focal cortical syndrome. We will review data that provide evidence of intrahemispheric disconnection, in particular within the right hemisphere's frontoparietal networks connected by the superior longitudinal fasciculus. Recent findings suggest that interhemispheric disconnection could also contribute to the manifestations of USN. Most importantly, interhemispheric disconnection might be a predictive factor for the chronicity of this disorder. This hypothesis implies that the left hemisphere by itself is not able to compensate for the patients' deficits. Recovery requires the ability to exchange information between the two hemispheres, particularly in the posterior parietal and occipital regions.