Mechanically evoked perioral reflexes in infants.

Mechanically evoked activity in the superior and inferior segments of the orbicularis oris muscle was sampled in several young infants using a specially designed position-servo linear motor and a pacifier instrumented with eight miniature EMG electrodes. Unilateral stimulation of lip vermilion resulted in short latency, bilateral activation of the upper and lower lip recording sites. The ontogenesis of facial reflex sensitivity to mechanical inputs is discussed in relation to the acquisition of motor skills, including speech and smiling.