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 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.