Intrinsic dynamics and mechanosensory modulation of non-nutritive sucking in human infants.

The human infant is endowed with a complex mechanism for the ingestion of nutrients that becomes functional in late fetal life. The sucking motor pattern is generally accepted to be under the control of pattern generating circuitry located in the brainstem reticular formation. Systems under the control of a central pattern generator (CPG) may use afferent feedback to allow for changing environmental conditions. Although it is clear that afferent pathways serving the orofacial region become responsive to mechanical stimulation early in fetal life, little is known about the integration of afferent information into the suck CPG. The actifier, a device for the mechanical stimulation of intraoral and perioral tissues, was designed and used to investigate the response properties of the human infant suck CPG to patterned mechanical stimulation. Sinusoid and square waveform stimuli elicited responses including modulation of jaw kinematics and synchronization [entrainment] of non-nutritive suck motor patterns to the mechanical stimulus. These data provide evidence that the suck CPG is responsive to mechanical stimulation of perioral and intraoral soft tissues.