Phase-specific stimulation of prefrontal beta oscillations modulates distinct cognitive processes

Oscillatory phase has been proposed to organize neural information processing, but whether endogenous phase can be leveraged to causally shape human cognition remains unclear. Here, we tested whether repetitive transcranial magnetic stimulation (rTMS) delivered at specific phases of endogenous beta oscillations over the left dorsolateral prefrontal cortex modulates working memory and response inhibition. Participants received EEG phase-controlled, closed-loop rTMS delivered at either the peak or trough of their endogenous beta rhythm, using each participant's dominant beta frequency (20-30 Hz). A conventional 20-Hz rTMS delivered independently of the beta phase served as an active control. Compared to this control and each other, peak-targeted rTMS improved response inhibition, whereas trough-targeted rTMS improved working memory. Both phase-specific behavioral effects were accompanied by corresponding increases in event-related potentials, which were not observed after conventional stimulation. Across participants, behavioral improvements correlated with stimulation-induced electrophysiological changes. Finally, phase-specific rTMS induced distinct DLPFC network expansions that complemented the behavioral effects: peak stimulation enhanced posterior centro-parietal connectivity for inhibitory control, while trough stimulation expanded anterior prefrontal networks for working memory. These findings provide first evidence that opposite phases of endogenous prefrontal beta oscillations coordinate distinct cognitive and neural processes. This establishes prefrontal beta phase as a causal dimension for shaping executive function and as a target for prefrontal rTMS to modulate cognition and non-invasively probe phase-dependent brain function.