Neural Mechanisms of Cognitive Flexibility and Interference Control in a Stroop Task Switching Paradigm

Task-switching paradigms, often used to study cognitive flexibility, frequently employ incongruent bivalent stimuli, triggering two tasks and potentially conflating cognitive flexibility with interference control. This study assesses cognitive flexibility using univalent stimuli (triggering one task) and congruent bivalent stimuli (same response across tasks) in a modified Stroop task to investigate well-established neural activity correlates of cognitive flexibility, manifested in human (females and males) electroencephalography (EEG) recordings, while isolating switch process from the influence of interference control at the response level. In particular, we analyzed EEG theta-band activity and event-related potential (ERP) components in switch (N2, P3a, P3b, late sustained potential (LSP)) and interference (N400, LSP and mid-frontal theta activity) conditions. We compared each of the switch and the interference condition to the control condition using cluster-based permutation test. In the switch condition, we observed fronto-central N2, reduced frontal P3a, and a positive occipital LSP. The interference condition showed increased frontal theta, parietal N400, and a positive occipital LSP. We also compared switch and interference conditions using cluster-based permutation test. We observed a larger N2 in the frontocentral regions during the switch condition and higher frontal theta activity during the interference condition, which aligns with their comparisons to the control condition. This result suggests that distinct neural mechanisms are used for each of the processes involved in conflict monitoring. Specifically, the theta activity may reflect sustained monitoring and conflict resolution during interference, while the N2 may reflect more transient conflict detection and the need to switch task sets. Significance StatementCognitive flexibility--the ability to adapt behavior to a changing environment--is essential for goal-directed actions. For assessing cognitive flexibility unlike the typical approach, we did not use incongruent bivalent stimuli. We used univalent and congruent bivalent stimuli to isolate cognitive flexibility while assessing interference control separately with incongruent bivalent stimuli. We analyzed well-documented brain activities related to cognitive flexibility (P3b, N2, P3a, LSP) and interference control (N400, LSP), and mid-frontal EEG theta activity. Despite using different stimuli, we observed all expected components associated with the switch process except for the P3b. Both processes share common parietal activity, and while the frontal lobe plays a role in both, its activity differs between them.