Interactions between alertness and spatial awareness

Unilateral neglect, a common consequence of a stroke, involves a difficulty with detecting and responding to contralesional stimuli. It has been shown to be a heterogeneous syndrome, involving a cluster of deficits in both spatial and nonspatial functions. Studies have shown that patients with neglect can suffer from problems with sustained attention, spatial working memory, temporal processing, and alertness, as well as the more obvious deficits in spatial orienting. One of the most intriguing features of neglect is the widely observed hemisphere lateralisation of the disorder. Neglect is more common, and more persistent, after right hemisphere lesions. Attempts to explain this lateralisation have generally focussed on hemispheric differences in the control of spatial attention. Kinsbourne (1987), for example, suggests that the right hemisphere controls the ability to orient attention to both sides of space, whilst the left hemisphere is only able to orient attention to the right side of space. An alternative theory is that the right hemisphere is specialised for the control of certain nonspatial functions, and it is the presence of deficits in these right hemisphere-lateralised functions which exacerbates spatial orienting in patients with unilateral neglect. This thesis explores this latter hypothesis and its implications, using a variety of techniques, including psychophysiology, neuropsychology, functional neuroimaging, and psychopharmacology. The central hypothesis of the thesis is that there is a direct link between nonspatial factors and spatial awareness, such that declining alertness or reduced cognitive resources may be sufficient to induce a rightward shift in spatial bias.EThOS - Electronic Theses Online ServiceGBUnited Kingdo