Activity of intrinsic laryngeal muscles in fluent and disfluent speech

The goal of the present experiment was to determine if stuttering is associated with unusually high levels of activity in laryngeal muscles. Qualitative and quantitative analyses of thyroarytenoid and cricothyroid recordings from 4 stuttering and 3 nonstuttering adults revealed the following: Compared to periods of fluent speech, intervals of disfluent speech are not typically characterized by higher levels of activity in these muscles; and when EMG levels during conversational speech are compared to maximal activation levels for these muscles (e.g., those observed during singing and the Valsalva maneuver), normally fluent adults show robust and sometimes near maximal recruitment during conversational speech. The adults who stutter had a lower operating range for these muscles during conversational speech, and their disfluencies did not produce relatively high activation levels. In summary, the present data require us to reject the claim that adults with a history of chronic stuttering routinely produce excessive levels of intrinsic laryngeal muscle activity. These results suggest that the use of botulinum toxin injections into the vocal folds to treat stuttering should be questioned.