Novel insights into speech production networks of adults with developmental stuttering as revealed by analyses of speech intention, syllable frequency, and long-term therapy effects

Abstract

Objective: The neurophysiological correlates of the likely occurrence of a stuttering event are still unknown. This sensor-level EEG study investigated whether the transient formation, i.e. decrease in alpha and beta power, of the speech production network due to speech intention may lay open such neurophysiological marker. The modulation of alpha and beta power is associated with changes in the sensorimotor state indicating the maintenance or release from the current cognitive and/or sensorimotor state.Methods: We used time-frequency analyses to study alpha (8-13 Hz), low beta (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) and high beta (25 -30 Hz) power in 19 adults with developmental stuttering (AWS) and 19 fluent controls (FC) during speech intention. A cue-target reading paradigm separated preparatory activity of the speech production network during speech intention from language related processing.Results: During overt compared to covert speech intention, alpha and low beta power was reduced in both groups. A decrease in alpha and beta power relative to baseline emerged however only over posterior EEG sensors covering parietal regions, possibly indicating that the intention to read prevailed over the intention to speak. Further, prior to fluent speech, stuttering severity was associated positively with a significant increase in low beta power in EEG sensors covering left parietal, central and right temporal regions. This association was less pronounced prior to stuttered speech. No other differences emerged.Conclusion: Similar to fluent speakers, AWS show oscillatory activity modulations during the intention to speak overtly. However, in persons with more severe stuttering this task setup is overlaid with stronger beta power increase, possible implicating a stronger maintenance of the current sensorimotor state.2. Increased right frontal beta power during speech intention in severe stuttering