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Distinct patterns of activity within the anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (dlPFC) reported in neuroimaging studies during tasks involving conflict between competing responses have often been cited as evidence for their key contributions to conflict-monitoring and behavioural-adaptation, respectively. However, supporting evidence from neuropsychological patients has been scarce and contradictory. We administered a well-studied analogue of the Wisconsin Card Sorting Test (WCST), designed to elicit conflict between two abstract rules, to a cohort of six patients with damage to ACC or dlPFC. Patients who had sustained more significant damage to the ACC were not impaired either on a measure of conflict cost nor on measures of conflict-induced behavioral adaptation. In contrast, damage to dlPFC did not affect the conflict cost measure but abolished the patients’ ability to adapt their behavior following exposure to conflict, compared to controls. This pattern of results complements the findings from non-human primates with more circumscribed lesions to ACC or dlPFC on the same task and provides converging evidence that ACC is not necessary for performance when conflict is elicited between two abstract rules, whereas dlPFC plays a fundamental role in behavioral adaptation.

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.

We investigated whether there are reliable crossmodal associations between foods/flavours and words in neurologically normal individuals. Participants were given a range of foods to taste, and had to rate each one along a number of dimensions. These included scales anchored with the words "takete/maluma" and "bouba/kiki". The results highlight the existence of robust crossmodal associations between complex foods/flavours and words in normal (i.e., nonsynesthetic) individuals. For example, crisps (potato chips) and cranberry sauce are rated as being more "takete" than brie cheese, while mint chocolate is rated as more "kiki" than regular chocolate. On the basis of these results, we suggest that our brains can extract supramodal/conceptual properties from foods/flavours (just as has been demonstrated previously using auditory and visual stimuli) and meaningfully match them crossmodally. The possibility that this process is based on the global Gestalt of a food rather than on any specific sensory qualities is also discussed. © 2010 Psychology Press.