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Title: Chromatic processing in hemianopia
Author: Ridgway, Nicola C. T.
ISNI:       0000 0004 2668 2302
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2009
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Occipital brain lesions result in a homonymous visual field defect termed corticol blindness. Some residual visual discrimination capabilities within the field defect may persist even when the patient does not report awareness of visual stimuli restricted to the blind field. This is termed blindsight and has been documented for the detection and discrimination of a range of visual attributes. Previous research investigating detection and discrimination of visual stimuli at different wavelengths presented within the field defect has broadly led to two main conclusions. Firstly, that chromatic detection ability is largely intact except for an overall attenuation of sensitivity. Alternatively, it has been found that there is selective sparing of sensitivity to long wavelengths compared to medium and short wavelength stimuli. In the current thesis, two indirect techniques (the redundant target effect and the saccadic distractor effect) have been adopted to further investigate residual chromatic abilities within the blind field. A complex pattern of findings were demonstrated for all patients tested showed evidence of chromatic processing consistently for targets presented in their blind field. Of particular interest is the evidence of processing of S cone sensitive stimuli, as S cone afferent signals reportedly, to not project to midbrain structures such as the superior colliculus, a structure often implicated in blindsight.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available