ACTIFIER II: The Dynamics of Sensorimotor Integration during Suck in Neonates and Infants
S Barlow, D Finan, L Seibel, S Stumm, S Ponnaboyina, R Shantha, R Konopacki
Recent work in adults has shown that the excitability of trigemino-facial pathways modulates in a phase-dependent manner during evolving motor action. Key determinants include the level of active lip force, and the rate of force recruitment during lip compression maneuvers (Andreatta, Barlow, Finan & Biswas, 1996, JSHR; Andreatta & Barlow, 2003, Exp Brain Research). The ontogeny and specificity of sensorimotor integration among orofacial muscle systems remains largely unknown in neonates and infants. The current report considers the modulation of somatic sensory pathways during spontaneous, centrally patterned motor output in neonates and infants. ACTIFIER II technology was used to deliver punctate mechanical inputs under force-feedback to the face during non-nutritive suck (NNS). Stimulus timing was referenced to a series of suck pressure thresholds using real time waveform discrimination on the NNS suck pressure signal. Evoked activity among lip muscle sites was sampled using a new miniature hydrogel Ag/AgCl electrode array. Mechanical stimuli generated by the ACTIFIER II system are effective in evoking the early component of the trigemino-facial response among perioral muscles of infants. Developmentally related changes in the latency, specificity, and growth function of the R1 component of the mechanically evoked perioral response is consistent with observations of upper limb motor function suggesting that the transition of simple reflex processing to more elaborate forms of sensorimotor actions for voluntary reactions is fundamental to motor skill acquisition (Bawa, 1981).