A quantitative analysis of visual perceptual tasks for use in schizophrenia research

Abstract

Schizophrenia is a neurological disorder that is primarily associated with hallucinations, delusions and disordered or confused thinking. Additionally, and less noticeably, the disorder is accompanied by a plethora of cognitive deficits and, as this thesis will address, sensory deficits. Historically, sensory deficits in patients with schizophrenia have been largely discounted. These deficits have instead been attributed to higher-order mechanisms such as impairments to attentional or emotional processing and often localised to the pre-frontal cortex or the limbic system. It is only within the last 50 years (Javitt, 2009) that schizophrenia research has awoken to the possibility of sensory deficits localised to the primary sensory cortices themselves. This thesis will focus on cataloguing potential mechanisms within the visual system which cannot be explained by higher-order processes alone but instead serve as an example of processing deficits in patients with schizophrenia which are likely to be present across the whole brain. Specifically, this thesis will investigate the feasibility of utilising established visual phenomena, through psychophysical and electrophysiological experimentation, within schizophrenia research. This document will first detail our current understanding of sensory deficits in patients with schizophrenia, with particular focus on lower level mechanisms such as gain control. It will also consider how they may be implemented within a clinical setting; this framework will inform all subsequent experiments. Three main experimental chapters will follow titled: "Assessing the functional significance of the Horizontal Effect"; "Correlations between visual oddball responses and schizotypy"; and "Adaptation to Orientation Regularity". Each of these experiments represents an attempt at creating a novel visual paradigm for use within clinical populations which will advance our knowledge of how the visual system performs in patients with schizophrenia. The final chapter will draw upon the conclusions reached from each of the experimental programs and assess future directions for both the current program as well as the field itself.

Date of Award	2017
Original language	English