Ontogeny of infantile oral reflexes and emerging chewing.

The ontogeny of rooting, lip, lateral tongue, mouth opening, biting, and Babkin reflexes and emerging chewing behaviors were observed in 2 normal infants from 1 week to 35 weeks of age. These behaviors were videotaped at 9 monthly test sessions, and their movement patterns analyzed during slow-motion playback. The reflex responses were elicited in both infants through 35 weeks of age. They consisted of those characteristic movements described in the literature plus additional movements that elaborated the characteristic pattern. The complexity of the reflexes and the quality of movement changed with age. Components of chewing, which emerged sequentially from 1 week of age, were cyclical mandibular elevation and depression, lateral tongue movements, transport of the bolus from lateral to medial oral position, mandible retrusion, lateralization and protrusion movements in association with mandibular elevation and depression, increase in speed of rhythmical chewing movements to the mature speed of 1 cycle per second, and mastication. Chewing and oral reflexes contained similar movements but differed in the relative frequency of certain characteristic movements and in the stimulus response relationship.