Chechlacz, Magdalena
(2012).
The neuroanatomy of visuopatial awareness - lessons from lesion symptom mapping and diffusion tractography in neglect, extinction and simultanagnosia.
University of Birmingham.
Ph.D.
Abstract
The work presented in this thesis explored the structural and functional organization of visuospatial attention. This was done through advanced voxel-wise lesion symptom mapping
methods used to decompose neuroanatomy of visuospatial disorders. The first study contrasted the neural substrates of different neglect symptoms, specifically the contributions of common and dissociable grey and white matter changes linked to allocentric and egocentric neglect. Two following studies decomposed the neuroanatomy of frequently co-occurring spatial attention syndromes by examining (1) the lesion patterns associated with visual and tactile extinction vs. those related to visual field defects and neglect, and (2) the lesion pattern linked to simultanagnosia, extracting out lesions associated with unilateral visuospatial deficits. These studies demonstrated that the different patterns of grey matter lesions in individual patients, and the laterality of white matter disconnections, determine the degree to which visual processing and spatial attention are disrupted and thus the nature of the observed cognitive symptoms. The final study examined the neuroanatomy of subacute relative to chronic neglect and whether persistent neglect symptoms could be predicted based on clinical computed tomography scans acquired at stroke diagnosis. The findings provided evidence that although wide spread lesions are associated with acute symptoms, only some of these are critical for predicting whether neglect will become a chronic disorder. The pro’s and con’s of different approaches to lesion-symptom mapping are discussed, along with the theoretical implications for understanding the nature of human visual attention.
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