Multimodal examination of brain networks involved in attentional biasing in schizophrenia

Schizophrenia is a serious, chronic mental illness that is characterized by perceptual abnormalities and cognitive deficits. Although the illness is commonly associated with perceptual abnormalities, the cognitive deficits have the greater impact on functional outcomes in patients. Some of the most profound deficits in schizophrenia have been observed in a domain referred to as cognitive control. Cognitive control is defined as the ability to adaptively adjust behaviour in response to environmental changes. Given the broadness of this definition, cognitive control is often fractionated into constituent cognitive operations, such as goal representation and maintenance, attentional biasing, conflict resolution, and stimulus-response mapping. In this study, the goal was to examine the brain basis for deficits in the attentional biasing aspect of cognitive control in schizophrenia. Behavioural and brain mechanisms of attentional biasing were assessed by manipulating the number of features that participants would have to ignore for each experimental trial. As schizophrenia is characterized by changes to both brain structure and function, a further aim was to use multi-modal brain imaging to develop a comprehensive picture of changes that underlie difficulties in attentional biasing. The results of this study indicated that although schizophrenia patients exhibit changes in brain structure, they still utilized the same brain networks as neurologically healthy individuals to bias attention towards relevant stimulus features. For the functional magnetic resonance imaging results, a functional brain network underlying attentional biasing, which included the dorsal anterior cingulate cortex, was identified and showed a positive relationship between the number of irrelevant stimulus features and increases in brain activity. Patients, however, showed reduced compensatory modulations in brain activity as the number of irrelevant stimulus dimensions increased. The magnetoencephalography results showed differences between the schizophrenia patients and healthy participants, but these differences were not as hypothesized, and may reflect cognitive differences related to language processing in schizophrenia. This work suggests that brain activity in patients is less efficient at higher levels of task difficulty when performing an attentional biasing task but these results are clouded by underlying changes in brain structure and a high variability in task activity in the patients.Medicine, Faculty ofGraduat