Thesis Working Title:  Investigation of Visual Hallucinations in Parkinson’s Disease

Visual hallucinations are the most common symptom of psychosis in Parkinson’s disease. They are debilitating and negatively impact quality of life. This project will investigate a theoretical model of psychosis which posits that perceptual disturbances such as visual hallucinations arise from an over-reliance on prior, internal beliefs about sensory information - i.e. an expectation bias. The investigation will be empirical and cross-sectional, and comprise a behavioural task session (visual motion discrimination task) with simultaneous EEG, and neuropsychological assessments. Participants will be recruited from the New Zealand Brain Research Institute’s (NZBRI) ongoing longitudinal Parkinson’s disease study. These behavioural studies will be conducted and analysed with an emphasis on formal mathematical modelling of the neural processes involved in hallucinations. There will also be a focus on structured neuropsychiatric interviewing, conducted in parallel with the experimental tasks, to formally identify and characterise types of visual hallucinations and investigate any common themes. As a result, the project should make important advances in formalising our knowledge of hallucinations in Parkinson’s disease.