Year: 2016
Type: dissertation
Study design: Observational Study
Abstract: Reductions in drive and goal-directed behaviour have long been described as key features of schizophrenia. This thesis contains several investigations into the motivational deficits present in people with schizophrenia. Despite not being required for the diagnosis, motivational deficits were found to be a highly prevalent feature of the disease, even among younger patients who were relatively early in their course of illness. Using cross-sectional and longitudinal follow-up study designs, and across two studies with different participants, motivational deficits were found to hold strong predictive value for the determination of functional outcomes. After establishing the importance of motivational deficits in terms of outcomes, underlying behavioural mechanisms were explored using experimental paradigms. Several candidate reward processes were examined concurrently, including valuation of outcomes, estimation of the costs associated with obtaining outcomes, and learning the association between actions and outcomes. Our results provide support for the proposal that individuals with schizophrenia have impairments in their ability to compute effort demands, and that these impairments translate into real-world reductions in goal-directed behaviour. Beyond mechanisms, this thesis also examined the inter-relationship between motivational deficits and another key domain of psychopathology in schizophrenia, namely, cognition. Although these two domains are thought of as distinct, two studies included in this thesis provide empirical evidence of an association, which is interpreted within a theoretical framework whereby poor motivation translates into reduced effort put forth during cognitive testing, which ultimately results in poorer submaximal test performance. Finally, the last study included in this thesis addresses the issue of treatment-induced symptoms. This study failed to find support for the contention that treatment with antipsychotic medications necessarily worsens the severity of motivational deficits in schizophrenia. Taken together, these investigations highlight the importance of motivational deficits in schizophrenia, and lay the foundation for a mechanistic understanding of these impairments.
Source: TSpace (University of Toronto)
Author: Gagandeep Fervaha
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2614283759