Different speech disorders are being studied to determine whether their patterns of impairment suggest independent components of the speech production process such as movement planning, preparation, programming, pacing, coordination, execution and sensory modulation. Studies in oral-lingual dyskinesia are examining whether movement abnormalities are related to excessive and irregular muscle activations interfering with normal movement, a lack of voluntary muscle activity and/or hypersensitivity to sensory or motor feedback. Excessive lateral-medial deflection of jaw movement was found during speech. Also, the ratio of the peak increase in muscle activation for movement over resting levels was reduced in oral-lingual dyskinesia. Chronic adult stutterers and normal speakers are being examined during fluency enhancing conditions to determine whether vocal fold position prior to speech onset is related to dysfluency. In normal controls, pharyngeal pressure levels and the velocity of pressure changes were altered during fluency enhancing conditions. Further, during """"""""hard"""""""" and """"""""soft"""""""" voice onsets, vocal fold position prior to phonation onset is modified in normal controls. The same studies in stutterers will examine whether vocal fold position prior to speech onset is related to the occurrence of dysfluencies.
