Assessment of oral-motor reflexes in stutterers and normal speakers: preliminary observations

Reflex responses of nine stutterers and nine normal speakers to low-level tactile and auditory stimuli were measured as changes in isometric molar biting force and masseter muscle activity. Tactile stimuli (mechanical displacement of the tissue) were applied to five intraoral and perioral sites. The acoustic stimulus was noise gated on for 12 msec. These low-level stimuli significantly modulated jaw-closing force and muscle activity in most of the subjects tested. In general, the initial effect of both auditory and tactile stimuli was suppression, although the initial response was excitation in some subjects with some forms of tactile stimulation. Within both groups of subjects, the amplitude and direction of reflex responses, particularly to mechanical stimuli, were highly variable between subjects, but these measures were stable within an individual over repeated tests.