Distinct oscillatory dynamics underlie different components of hierarchical cognitive control.

Hierarchical cognitive control enables us to execute actions guided by abstract goals. Previous research has suggested that neuronal oscillations at different frequency bands are associated with top-down cognitive control, however, whether distinct neural oscillations have similar or different functions for cognitive control is not well understood. The aim of the current study was to investigate the oscillatory neuronal mechanisms underlying two distinct components of hierarchical cognitive control: the level of abstraction of a rule, and the number of rules that must be maintained (set-size). We collected electroencephalography (EEG) data in 31 men and women who performed a hierarchical cognitive control task that varied in levels of abstraction and set-size. Results from time-frequency analysis in frontal electrodes showed an increase in theta amplitude for increased set-size, whereas an increase in delta was associated with increased abstraction. Both theta and delta amplitude correlated with behavioral performance in the tasks but in an opposite manner: theta correlated with response time slowing when the number of rules increased whereas delta correlated with response time when rules became more abstract. Phase amplitude coupling analysis revealed that delta phase coupled with beta amplitude during conditions with a higher level of abstraction, whereby beta band may potentially represent motor output that was guided by the delta phase. These results suggest that distinct neural oscillatory mechanisms underlie different components of hierarchical cognitive control. SIGNIFICANCE STATEMENT Cognitive control allows us to perform immediate actions while maintaining more abstract, overarching goals in mind and to choose between competing actions. We found distinct oscillatory signatures that correspond to two different components of hierarchical control: the level of abstraction of a rule and the number of rules in competition. An increase in the level of abstraction was associated with delta oscillations, whereas theta oscillations were observed when the number of rules increased. Oscillatory amplitude correlated with behavioral performance in the task. Finally, the expression of beta amplitude was coordinated via the phase of delta oscillations, and theta phase coupled with gamma amplitude. These results suggest that distinct neural oscillatory mechanisms underlie different components of hierarchical cognitive control.