Cognitive and brain mechanisms of visual spatial attention and awareness

The proposed research will investigate brain mechanisms underlying our ability to orient our attention in space and mechanisms giving rise to conscious experience of visual events. Moreover, it will investigate how these cognitive processes can be affected following damage in particular areas of the brain. Often such damage leads to spatial neglect, a complex neurological syndrome frequently observed following stroke, characterised by loss of awareness for the left side of space, and an inability to orient one's attention towards that side. We will use a variety of techniques including brain imaging techniques, behavioural and clinical measures, to identify the role of distinct anatomical areas in the healthy human brain involved in spatial attention and awareness, how these are affected in patients with neglect, and how in turn these patients can improve following prism adaptation, a new promising rehabilitation method. This research, which will be conducted at the MRC-CBU unit in Cambridge, is both of scientific and clinical interest: it aims to increase our understanding of cognitive mechanisms underlying spatial attention and awareness in the healthy human brain and also to reveal mechanisms underlying severely debilitating neurological conditions following brain damage, aiming to produce recommendations for their diagnosis and treatment.

The proposed research will investigate how the cognitive functions of visual-spatial attention and awareness are implemented in the human brain and how these processes can be affected following brain damage (e.g. spatial neglect). Spatial neglect is a multi-component neurological syndrome frequently observed following stroke, providing a unique window for studying how the normal brain implements spatial attention and awareness and exerts cognitive control upon these. Most commonly, neglect includes losses in awareness, attention and exploration towards the contralesional (left) side of space and arises after right hemisphere damage, although the exact anatomy of the syndrome is still unclear. The proposed programme involves three particular lines of research. The first aims to investigate the distinct role of right parietal and frontal cortex (damage to either potentially leading to neglect) in attentional functions during visual search, in line with the emerging view that neglect may arise due to disruption of a fronto-parietal attentional network. This will involve testing how visual search efficiency across space is affected with increasing attentional demands in patients with right parietal versus right frontal lesions. Moreover, using fMRI, we will be testing for the functional implications of such lesions in visual search, and comparing it to normal function. Apart from clarifying the role of parietal and frontal cortices in normal spatial attention, this research will help clarify the role of these distinct anatomical areas in the neglect syndrome. The second line of research will investigate how neglect, highly debilitating in everyday life, associated with poor outcome and substantial health costs, may be ameliorated following cognitive rehabilitation, and will aim to produce recommendations its diagnosis and treatment. In particular we will investigate cognitive mechanisms behind neglect improvement following prism-adaptation, a new promising rehabilitation approach, involving the use of prism-glasses, asking whether the already proven beneficial impact of prisms on neglect is due to a genuine reduction of the rightward bias, characteristic to neglect, or due to more strategic 'top-down' corrections. We hope that our results will enable the design of more efficient treatment protocols in the future. The last line of research involves the use of MEG to study neural mechanisms underlying visual awareness, by studying patients with visual extinction, a frequent neglect component, offering a unique opportunity to uncover neural correlates of both conscious and unconscious visual processing. This investigation will add to the growing and controversial debate on the role of early visual areas in conscious experience, as well as the role of 'higher cognitive' areas in this.