Novel primitive swallowing reflex: facial receptor distribution and stimulus characteristics

We recently described a primitive swallowing reflex: swallowing as a response to a puff of air administered to the face. To identify the facial afferent distribution of this response, the necessary characteristics of the stimulus, and the role of the infant's antecedent behavior, we studied 13 infants who had demonstrated this reflex. We evaluated nine infants by clinically observing for swallowing in response to a total of 135 stimulus applications. All nine had consistently positive responses to the maxillary-ophthalmic area and to the maxillary-mandibular area. Two had consistent responses to stimulation of the mandibular area alone; these were positive. Six had consistent responses to stimulation of the ophthalmic area alone; these were negative. Four infants, evaluated by manometric documentation of swallowing (a total of 137 stimulus applications) demonstrated 47 of 79 (59%) positive responses to stimuli applied to facial areas including any parts of the lips, but only 7 of 28 (25%) positive responses to stimuli applied to facial areas excluding all parts of the lips (chi-square P = 0.002). Light touch to any facial area, including the cornea, failed to produce a swallow in any infant. Crying and sleep were incompatible with the reflex. This newly identified primitive swallow reflex seems to require diffuse stimulation, possibly thermal, to the perioral area of the face in an awake and noncrying infant.