Understanding The Brain Networks Underlying Cognition

Abstract

The advancement of magnetic resonance imaging (MRI) has allowed us to begin to explore how brain regions work collectively in order to produce important functions. The cognitive control network (CCN)—involving the dorsolateral prefrontal cortex, the dorsal parietal cortex and the dorsal anterior cingulate cortex—is associated with the production of goal-directed or “cognitive control” behaviors, which are imperative to our intellectual, social and emotional processes. However, how certain properties of this network directly relate to function is yet to be established. This thesis aimed to use structural and functional MRI to examine how changes in this network over time relate to behavioral change in order to better understand the mechanisms of cognitive control. The first three chapters linked task-related functional activity and connectivity in the CCN, structural development of the CCN and intrinsic connectivity of the CCN and a related network (the default mode network (DMN)), to change in behavioral ability over time in healthy controls. Finally, we examined how CCN and DMN activity may vary in mood disorders in which cognitive control function is impaired. Across all three analyses of the CCN in healthy controls we found change in volume, connectivity and activation of the dorsal parietal node to have a relationship with change in behavior. Additionally, all these relationships were independent of age, introducing the possibility that change in this circuitry is being driven by experience-dependent mechanisms. Finally, we found that failure to suppress the DMN, which is typically down-regulated during cognitive tasks, is a common feature of asymptomatic bipolar and unipolar depressive disorders and could relate to cognitive control dysfunction. This work helps in understanding the neural correlates of cognitive control function and, with future work, could aid in the development of targeted treatments to address cognitive control dysfunction.