Persistent developmental stuttering as a cortical-subcortical dysfunction: evidence from muscle activation.

BACKGROUND One contemporary view of stuttering posits that speech disfluencies arise from anomalous speech motor control. PURPOSE To verify the rest muscle tension and speech reaction time of fluent and stuttering adults. METHOD 22 adults, divided in two groups: G1--11 fluent individuals; G2--11 stutterers. Electromyography recordings (inferior orbicularis oris) were collected in two different situations: during rest and in a reaction time activity. RESULTS The groups were significantly different considering rest muscle tension (G2 higher recordings) and did not differ when considering speech reaction time and muscle activity during speech. There was a strong positive correlation between speech reaction time and speech muscle activity for G2--the longer the speech reaction time, the higher the muscle activity during speech. CONCLUSION In addition to perceptible episodes of speech disfluency, stutterers exhibit anomalies in speech motor output during fluent speech. Correlations with a possible cortical-subcortical disorder are discussed.