Dynamics of cognitive control and flexibility in the anterior cingulate and prefrontal cortices

The body of work hereby presented aims at better defining the specific mechanisms underlying cognitive control and flexibility, and to investigate the neural substrates that might support these dynamics. More specifically, the anterior cingulate (ACC), dorsolateral prefrontal (dlPFC) and frontopolar (FPC) cortices have been proposed to play a fundamental role in monitoring and detecting the presence of environmental contingencies that require the recruitment of cognitive control (such as competition between responses in the presence of conflicting information), implementing cognitive control, and supporting higher-order cognitive processing, respectively. This thesis investigates the effects of damage to these regions, and of interference with their activity, on these processes. It also argues for the importance of dissociating possible separate cognitive control components that might differently contribute to behavioural adjustments (such as caution and attention/task-relevant processing), and provides one of the first attempts to quantify them within the parameters of a mathematical model of choice response-time, the Linear Ballistic Accumulator (LBA). The results confirm the crucial role of the dlPFC in modulating behavioural adjustments, as both damage and interference with this region’s activity significantly affect measures of conflict-induced behavioural adaptation. It is hypothesized that dlPFC might drive behavioural adjustments by encoding recent conflict history and/or supporting the automatization of a newly advantageous behavioural strategy during the early stages after a change in conflict levels. When a task does not involve competition between a habit and instructed behaviour, lesions or interference with ACC’s activity do not appear to affect behaviour in a manner that is consistent with the classic conflict-monitoring framework. It is suggested that its role might be better described as a more general monitoring and confirmatory mechanism that evaluates both actual and potential outcomes of an action, in order to proactively guide adjustments away from contextually disadvantageous responses. Finally, lesions to the FPC do not affect abstract-rule integration, but do impair the early stages of acquisition of a new abstract rule, when a previously rewarded rule stops being rewarded, and specifically when acquisition is dependent on self-initiated exploration. This suggests a role for FPC in the evaluation of multiple concurrent options in order to aid the development of new behavioural strategies.This thesis is not currently available in OR