Introduction: Cognitive ‘conflict’ arises when multiple response tendencies compete for behavioral expression. Human neuroimaging and electrophysiologic studies have framed a conflict network involving the medial and lateral prefrontal cortices, with some data suggesting that high gamma oscillations may contribute to conflict processing, but the location, timing, and role of these oscillations remain to be characterized.
Methods: We recruited human subjects (n = 2) undergoing intracranial EEG monitoring for epilepsy to perform two validated conflict tasks. During these tasks, we recorded local field potentials from depth electrodes implanted in the frontal and temporal lobes (n = 198 contacts). High gamma (80-150 Hz) power was extracted using wavelet convolution.
Results: Subjects performed the tasks accurately (98% and 99% correct) and demonstrated anticipated conflict-induced response slowing (p < 0.001 for each task and subject). Event-related potentials revealed widespread task-related activity, with similar distributions and time courses between the two tasks.
Sustained elevations in high gamma (> 1 dB for > 100 ms) during the pre-response period were observed almost exclusively at a subset of sites in the lateral more than medial frontal lobes, with the signal at nearly all sites demonstrating windows of sensitivity to the level of conflict present in the task trials.
High gamma activation sites in the lateral and medial prefrontal cortices clustered in the middle frontal gyri and midcingulate and pre-SMA, respectively. Among the lateral sites, >50% in either task demonstrated a trial-by-trial dose-response correlation between the magnitude of early high gamma activity and the degree of experienced conflict, as indexed by subsequent reaction time.
Conclusions: High gamma oscillations in the dorsolateral prefrontal cortex are sensitive to conflict and predict reaction times, suggesting a possible neurophysiologic mechanism supporting conflict resolution.
Patient Care: Characterizing the spatiotemporal dynamics of conflict processing may ultimately inform rational neuromodulation strategies for patients with dysfunction in the putative conflict network, including those with obsessive-compulsive disorder and post-traumatic stress disorder.
Learning Objectives: By the conclusion of this session, participants should be able to: (1) define cognitive conflict, (2) describe the neural network involved in conflict processing, and (3) identify the contribution of high gamma oscillations to conflict resolution.