Surface EMG recording of the perioral reflexes: preliminary observations on stutterers and nonstutterers

The capability to record muscle-specific reflexes in the perioral muscles with surface electrodes could have practical significance for the study of speech production disorders. In the present study, surface electrodes were used to describe the perioral reflexes in 7 stutterers and 5 nonstutterers. Electromyographic (EMG) recordings were obtained at electrode sites associated with the orbicularis oris inferior muscle (OOI) and depressor labii inferior muscle (DLI) during lower-lip press and depression gestures. During postural maintenance of these gestures, innocuous mechanical stimuli were applied at the corner of the mouth. Signal averages on the two EMG signals for the two gestures and electrode sites revealed four distinct reflex response components: two excitatory (E1 and E2) and two suppression components (S1 and S2). During lip pressing, the OOI electrode site showed a prominent E1 response in all subjects, and, during lip depression, the DLI site showed an initial S1-E2 response pattern in the nonstutterers. These observations are consistent with previous descriptions of the perioral reflexes involving intramuscular electrodes. Quantitative differences in the perioral reflexes were not seen in the stutterers and nonstutterers. However, a difference was noted in the pattern of reflex response between the two groups during lip depression at the DLI electrode site.