Little is understood about the origins of atypical scanpath formation in schizophrenia. This thesis presents a series of novel investigations which aimed to characterise the viewing abnormality and its correlate in schizophrenia and to investigate a range of putative causal mechanisms. Individuals with schizophrenia and non-clinical comparison participants completed smooth pursuit and ocular fixation tasks, mood assessment scales and free-viewing of novel visual stimuli. Patients also completed detailed clinical and neurophysical assessment. Results replicated findings of a ‘restricted’ style of visual scanning schizophrenia, characterised by reduced fixation and saccade frequency, increased fixation durations and reduced scanpath length. Patients also demonstrated increases in medial saccade amplitude, duration and peak velocity relative to non-clinical viewers. Viewing abnormalities were only minimally associated with clinical and demographic variables, occurred irrespective of the nature of the stimulus and conveyed high sensitivity and specificity in distinguishing cases from controls. Two studies manipulated attention to the viewing task in non-clinical viewers and patients respectively and suggested atypical scanning is not entirely attributable to diminished task engagement. Restricted scanning was associated with both heightened anxiety and increased interference by irrelevant visual features during fixation. A possible causal role of anxiety on distractibility and thus scanpath formation is tentatively proposed. Restricted scanpaths were associated with dimensions of neurocognitive functioning including working memory, short term verbal memory and verbal fluency. These patterns are argued to be consistent with a role of dysfunction of the dorsolateral prefrontal cortex in atypical scanpath formation. Finally, scanpath dysfunction was found to occur independently of impairments in smooth pursuit performance, suggesting the independence of neuroanatomical bases for these deficits.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:499304 |
| Date | January 2009 |
| Creators | Beedie, Sara A. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=26092 |
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