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dc.contributor.advisorMcKeefry, Declan J.
dc.contributor.authorChalla, Naveen K.*
dc.date.accessioned2012-01-24T17:48:39Z
dc.date.available2012-01-24T17:48:39Z
dc.date.issued2012-01-24
dc.identifier.urihttp://hdl.handle.net/10454/5343
dc.description.abstractThe work in this thesis is concerned with examining the retinal and cortical contributions to human trichromatic colour vision. Chromatic processing at the cortex level was examined using visual evoked potentials (VEPs). These responses were elicited by chromatic spot stimuli, which were manipulated in order to selectively activate the chromatic processing system. Chromatic processing at the retinal level was examined using the electroretinograms (ERGs) for which cone isolating stimuli were used to assess the nature of L and M cone inputs to cone-opponent mechanisms. The results from the VEP experiments suggest VEP morphology is dependent upon 1) chromatic and or luminance contrast content of the stimulus, 2) stimulus size, and 3) extent to which the chromatic stimulus activates either the L/M or S/(L+M) opponent mechanism. The experiments indicate that chromatic stimulation is indexed by large N1 component and small offset responses. Optimal stimulus size for chromatic isolation is 2-4 ° along L/M axes and 6° along S/(L+M) axis. From the ERG experiments, It has been shown that the low (12Hz) and high (30Hz) temporal frequency flickering stimuli can isolate the chromatic and luminance processing mechanisms in the retina. For low temporal frequency ERGs, the L:M ratio was close to unity and L/M phase difference was close to 180°. For high temporal frequency ERGs, the L:M ratio was more than unity and L/M phase difference was close to 90°. In addition to this, the variation in L:M ratio across the retinal eccentricity was also examined. These results suggest, for the chromatic processing, L:M ratio is close to unity independent of retinal eccentricity and individuals. For the luminance processing, L:M ratio is more than unity and depends upon the region of the retina being stimulated. These findings indicate the maintenance of cone selective input for the chromatic processing across the human retina.en_US
dc.language.isoenen_US
dc.rights<a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>.eng
dc.subjectColour visionen_US
dc.subject; Electrophysiologyen_US
dc.subject; Visual evoked potentialsen_US
dc.subject; Electroretinogramsen_US
dc.subject; Human trichromatic colour visionen_US
dc.subject; Chromatic processingen_US
dc.titleAn electrophysiological study of chromatic processing in the human visual system. Using visual evoked potentials and electroretinograms to study cortical and retinal contributions to human trichromatic vision.en_US
dc.type.qualificationleveldoctoralen_US
dc.publisher.institutionUniversity of Bradfordeng
dc.publisher.departmentBradford School of Optometry and Vision Scienceen_US
dc.typeThesiseng
dc.type.qualificationnamePhDen_US
dc.date.awarded2011
refterms.dateFOA2018-07-19T08:30:19Z


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