Reappraising Unilateral Neglect

Unilateral neglect in humans may occur following injury to either cerebral hemisphere. Patients may fail to respond to stimuli in the contralesional hemispace, even though there is no primary sensory or motor impairment. It is commonly believed that unilateral neglect results from parietal lobe damage, and that it is more common and severe after right than left hemisphere lesions. However, more recent evidence suggests that the disorder cannot be attributed to damage to any single brain region. The disorder in fact appears to reflect a more complex disruption of space-related behaviour. Unilateral neglect may occur because the contralesional hemispace is deprived of attentional resources, or because there is a pathological gradient of attention across the whole of extracorporeal space. Since attentional mechanisms may be involved in the selection of appropriate actions in space, unilateral neglect may ultimately be explained in terms of a disruption in the co-ordination of spatial attention and action (the premotor theory). We conclude that the diversity of behavioural anomalies subsumed under the label of unilateral neglect indicates that it may be fractionated along several dimensions, and that to understand the disorder we must acknowledge its inherent complexity and multifaceted natur