Insights into the neural mechanisms supporting cognitive stability and flexibility from human intracranial...

Cognitive control is the ability to direct behavior based on internal goals. Two core capacities of cognitive control are focusing attention on task-relevant stimuli while ignoring distracters (cognitive stability) and shifting between different goals/rules to guide behavior (cognitive flexibility). Despite extensive prior work, the precise neural mechanisms underlying these capacities remain incompletely understood. We review recent intracranial electroencephalography (iEEG) studies that speak to this question by employing probes of conflict-control (requiring stability) or task-switching (requiring flexibility). Synthesizing the findings, we propose two levels of mechanism. The first mechanism is oscillatory coordination of when and where control signals are routed, involving performance monitoring and subsequent control implementation. The former is mediated by medial frontal theta (∼4-8 Hz) oscillations supporting the propagation of conflict-control and task-switching signals across cortical/subcortical networks, alongside high gamma (HG; ∼70-150 Hz) activity indexing local regional engagement; the latter is mediated via beta (∼13-30 Hz) oscillations regulating whether task sets are maintained (stability) or updated (flexibility) in working memory. The second mechanism is neuronal population coding of task-relevant information. This is supported by neural partitioning of task sets into distinct subspaces to simultaneously represent both domain-general and domain-specific information. Our review and integrative synthesis offer a working hypothesis for a more precise characterization of how the human brain implements cognitive stability and flexibility, which may eventually provide biomarkers for psychiatric and neurological conditions characterized by impairments in these capacities.