Respiratory high-frequency oscillations in normal and stuttering speakers

Margaret E Denny, Purdue University

Abstract

A prominent feature of stuttering is the physically widespread nature of its symptoms. It is thus appropriate, in looking for the sources of the aberrant motor patterns observed in stuttering, to look for neural centers involved in movement production that (1) have similar widely distributed outputs and (2) might be expected to be activated during speech. The brainstem circuitry, or central pattern generator (CPG), that regulates metabolic breathing is such a neural source; moreover, research on stuttering subjects has suggested that respiratory function is disturbed in stuttering. The available evidence suggests that, in normal speakers, the respiratory CPG is not a dominant source of controlling inputs to the respiratory system during speech. The present study was designed to test the hypothesis that interactions between the respiratory CPG and neural centers involved in voluntary respiratory control may differ in stuttering and nonstuttering subjects. Bilaterally coherent high-frequency oscillations (HFOs) in the 60-110 Hz band in respiratory EMGs were used as an index of the strength of neural inputs associated with the operation of the metabolic respiratory CPG. Inspiratory-related EMGs were recorded from right and left sides of the anterolateral rib cage in 10 stutterers and 10 normal speakers matched for sex, age, and education as they read, performed a deep breathing task and a "speechlike" task that required them to mimic speech breathing without vocalizing. ECGs, audio and video recordings were obtained. For both groups, nonparametric comparisons of maximum coherence in the 60-110 Hz band did not show significant differences among experimental tasks. Normal speakers consistently showed comparable or reduced values of coherent HFOs for speech compared to deep breathing. Some stutterers showed a pattern not seen in normals: the highest values of coherence were associated with speech. These results suggest that the respiratory CPG is more active in some stutterers during speech than is typical. In addition, a repeated measures ANOVA showed a significant groups by tasks interaction: mean maximum coherence for deep breathing was greater in normal than stuttering subjects. These results suggest that stutterers differ from normal speakers in their management of interactions between metabolic and voluntary control systems for respiration.

Degree

Ph.D.

Advisors

Smith, Purdue University.

Subject Area

Neurology|Anatomy & physiology|Animals|Speech therapy

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