Electronic Thesis and Dissertation Repository


Doctor of Philosophy




Dr. J Bruce Morton


One standard task used to investigate the development of cognitive control is the Dimensional Change Card Sort (DCCS). Performance and patterns of brain activity associated with the DCCS show continued age-related advances into early adolescence. According to many theoretical accounts, the DCCS places demands on a single underlying executive control process. Three experiments examined the possibility that the DCCS places demands on multiple control processes that follow distinct developmental trajectories. In Experiment 1, rule switching and conflict processing made orthogonal contributions to DCCS performance. Rule switching was associated with a cue-locked late frontal negativity (LFN) event-related potential (ERP) and conflict processing was associated with stimulus-locked frontocentral N2. Moreover, rule switching and conflict processing followed distinct developmental trajectories. In Experiment 2, distributed cortical source models of the cue-locked LFN were associated with age-related differences in distributed network of regions associated with cognitive control. Source models of the stimulus-locked N2 were associated with conflict-related modulations in the anterior cingulate cortex (ACC) that varied as a function of age. In Experiment 3, dynamic modulations in conflict processing were associated with pronounced age-related behavioural and electrophysiological adaptations to prior conflict. Taken together the findings of the current set of studies suggest that multiple control processes underpin age-related advances in DCCS performance.