Sensorimotor alpha–beta phase–amplitude coupling is reduced in adults who stutter and predicts stuttering frequency: Implications for gain control

The sensorimotor dynamics that support speech motor stability remain incompletely understood. Developmental stuttering, which has been linked to dopaminergic dysregulation within basal ganglia–thalamo–cortical circuits, provides a useful model for probing these mechanisms. We tested whether alpha–beta phase–amplitude coupling (PAC) in sensorimotor mu rhythms is sensitive to sensorimotor regulatory processes, predicting that it would (i) differentiate adults who stutter (AWS) from fluent controls and (ii) relate to the frequency of stuttered trials excluded from EEG analyses. Whole-head EEG was recorded while AWS (n = 20) and controls (n = 18) planned and executed spontaneous speech. Independent component analysis isolated clean bilateral mu components localized to sensorimotor cortices. Event-related PAC (ERPAC) was quantified using a Gaussian-copula mutual-information estimator and cluster-based permutation testing. Across hemispheres, conditions, and trials, AWS exhibited reduced alpha–upper beta coupling (25–32 Hz), suggesting reduced sensorimotor coordination. Within AWS, planning–execution ERPAC differences predicted stuttering frequency in opposing directions across hemispheres, with a left-hemisphere bias emerging as the strongest predictor (marginal R2 = .33; conditional R2 = .82). These findings suggest that α–β ERPAC is sensitive to oscillatory coordination processes that may support sensorimotor gain regulation. Reduced ERPAC in AWS may reflect weakened coordination of sensory feedback with ongoing motor predictions, increasing vulnerability to instability during planning–execution transitions. These results identify α–β ERPAC as a promising candidate measure for future mechanistic and neuromodulatory studies in stuttering.