Dulude, Louise2013-11-082013-11-0820082008Source: Dissertation Abstracts International, Volume: 70-02, Section: B, page: 1371.http://hdl.handle.net/10393/29542http://dx.doi.org/10.20381/ruor-19800Attention dysfunction is a hallmark of schizophrenia, a disorder in which smoking prevalence is double that of the general population. The main interest of this dissertation was in using behavioural performance (accuracy, reaction time or RT) and brain event-related potential (ERP) measures to examine the processing of distracting events in schizophrenic patients and control subjects, and to assess the effects of acute nicotine on this processing. This was accomplished in three experiments by comparing 12 minimally-tobacco-deprived control smokers with 12 outpatient smokers, the latter being assessed under double-blind, placebo-controlled (vs. nicotine) conditions. Experiment 1 used a passive, non-task paradigm to examine the mismatch negativity (MMN) ERP component, an index of early auditory deviance detection. Patients exhibited reduced MMNs to frequency and duration deviants compared to controls, and nicotine increased patients' duration MMN to a level comparable to that seen in controls. Experiment 2 used a novel auditory-auditory distraction paradigm that embeds task-irrelevant deviant features within task-related stimuli requiring location discrimination. Deviants caused RTs to be prolonged in patients and controls. Patients' MMN did not differ from controls' but attentional switching, reflected in the P3a ERP, was attenuated in patients. Nicotine increased patients' MMN to small deviants such that it was no longer smaller than the MMN to large deviants. Experiment 3 used an auditory-visual distractor paradigm requiring participants to discriminate visual letters vs. numbers preceded by task-irrelevant auditory stimuli of standard and deviant frequencies. Reaction times were prolonged by deviants in patients and controls and the MMN of patients to small deviants was diminished. Nicotine increased the MMN to small deviants and reduced RT prolongation and the involuntary attentional switching indexed by the P3a ERP associated with large deviants. Overall, these experiments demonstrated that nicotine can reduce distractibility and can normalize aberrant neural processing of distracting events in schizophrenic patients.220 p.enPsychology, Experimental.Thesis