The effect of oral sensory deprivation on stuttering behavior.

To assess the role of oral sensation in the execution of a stuttering moment, six adult male stutterers, ranging in severity, provided samples of spontaneous speech in three experimental conditions: control, anesthetic, and placebo. In the anesthetic condition, sensory deprivation of the oral cavity was achieved by means of a series of nerve-block injections. The placebo condition involved insertions of a hypodermic needle but no anesthetic solution was injected. The speech samples were analyzed for frequency of stuttering by dysfluency type. In addition, severity ratings were made for all identified dysfluencies. The results indicated that oral sensory deprivation was associated with a significant increase in the frequency and severity of stuttering. This effect was particularly evident in the class of dysfluencies termed "prolonged articulatory postures." The results for the control and placebo conditions were not observed to differ. These findings were interpreted as evidence of both open-loop and feedback-dependent regulation processes during the moment of stuttering.