Respiratory control in stuttering speakers: evidence from respiratory high-frequency oscillations.

This study tested the hypothesis that, in stuttering speakers, relations between the neural control systems for speech and life support, or metabolic breathing, may differ from relations previously observed in normally fluent subjects. Bilaterally coherent high-frequency oscillations in inspiratory-related EMGs, measured as maximum coherence in the frequency band of 60-110 Hz (MC-HFO), were used as indicators of participation by the brainstem controller for metabolic breathing in 10 normally fluent and 10 stuttering speakers. In all controls and most stuttering subjects, MC-HFO for speech was higher than or comparable to MC-HFO for deep breathing. For 4 stuttering subjects, higher MC-HFO was observed for speech than for deep breathing. Comparison of deep breathing to a speechlike breathing task yielded similar results. No relationship between MC-HFO during speech and severity of disfluency was observed. We conclude that in some stuttering speakers, the relations between respiratory controllers are atypical, but that high participation by the HFO-producing circuitry in the brainstem during speech is not sufficient to disrupt fluency.