Master of Science (MSc)
Faculty of Science
Psychosis is a term given to a mental state described as a loss of contact with the real world. The aim of this thesis was to examine early non-specific psychotic experiences in a healthy population by means of two self-report screening tools: Prime Screen and Youth Psychosis At-Risk Questionnaire-Brief, and place individuals on a psychosis continuum. Across this psychosis continuum, three event related potential (ERP) components were assessed: P300, Mismatch Negativity and N100. There is evidence that P300 and mismatch negativity amplitudes diminish in individuals with psychosis. Similarly, impaired N100 amplitude suppression (increased N100 amplitudes) during vocalization has been observed in psychosis. In the first experiment, participants vocalized a series of ‘ah’ sounds that were recorded and later played back in a talk-listen paradigm. We proposed that N100 amplitudes while talking would be reduced as compared to listening. However, as risk of psychosis increases, we predicted a failure of this N100 suppression (higher N100 amplitudes in individuals with higher risk of psychosis) during talking. In the second experiment, participants completed an oddball task in which a series of standard tones were presented. Duration deviant tones elicited P300 and mismatch negativity ERPs. We predicted that P300 and mismatch negativity amplitudes would decrease with increasing risk for psychosis. Furthermore, by using data from both experiments, a combination of ERPs was used to assess how well they were predictive of risk. We concluded that although risk was not associated with any ERP component in our population, results were fairly consistent with the general pattern observed in previous literature among individuals at high risk for psychosis. The combination of both the oddball and talk-listen paradigms provided better risk predictability than either paradigm alone. These findings contribute to the development of a risk predictability model that should allow efficient assessment of psychosis risk and may improve the prognosis for people with psychotic disorders.
Rehman, Anaya, "Auditory ERP differences across a continuum of psychotic symptoms in non-clinical population" (2017). Theses and Dissertations (Comprehensive). 1927.