City Research Online

Abstract

Recent investigations have shown that the activity of the visual system in the processing of some stimulus attributes such as spatial structure and stimulus colour are reflected in the pupil response in the form of a small transient constriction at the stimulus onset. The response amplitude appears to be proportional to the level of activity generated and varies systematically with the properties of the visual stimulus.

In this report, it has been shown that the processing of coherent motion information can also produce pupillary changes in the form of pupil motion responses (PMRs). The results show that PMRs are present for both foveal and peripheral stimulus presentations and are not affected significantly by degradation of retinal image quality. It has been demonstrated that PMRs are also elicited to sudden changes in stimulus speed and direction, and that the response amplitudes vary systematically with the percentage change involved.

There are extensive psychophysical data showing that blindsight subjects are sensitive to movement information when the stimulus is presented in their blind field. In this study, pupillometric parallels for the psychophysical findings have been demonstrated.

Data which reveal the existence of residual chromatic discrimination in the absence of VI have also been obtained in two blindsight subjects. It has been shown that their psychophysical performance improves with the level of chromatic saturation of the stimulus.

The pupil colour responses have been investigated under similar conditions. Results show that the pupil responses to coloured stimuli can also be elicited in the blind field and that these responses parallel the psychophysical findings. The results obtained have been discussed in relation to the properties of the neuronal structures and visual pathways which are likely to mediate the observed pupillometric and psychophysical findings.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine > RZ Other systems of medicine
Departments:	School of Health & Psychological Sciences > Optometry & Visual Sciences School of Health & Psychological Sciences > School of Health & Psychological Sciences Doctoral Theses Doctoral Theses

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