Meeting Abstract
Sucking, a mammalian synapomorphy for infant feeding, requires multiple sensory inputs to facilitate coordination of multiple oropharyngeal structures. The recurrent laryngeal nerve (RLN) provides sensation for the lower vocal tract, and motor to intrinsic muscles of the larynx. It is critical for normal swallowing but is not thought to be involved in sucking. We tested the hypothesis that, as high levels of sensorimotor integration are essential for all stages of feeding, disruption of this pathway would influence sucking. We implanted radiopaque markers in the tongue, palate, hyoid, thyroid and epiglottis of infant pigs. Using digital videofluroscopy at 100 fps we recorded the animals feeding before and after unilateral RLN lesion. RLN lesion affected the position and movements of the tongue and hyoid. The location of structures differed between treatments, with tongue, hyoid and thyroid being held more cranially, and the epiglottis more caudally in lesioned animals. Ranges of movements differed, as well as relative expansion and contraction within the tongue. Variation in between cycle movements was less in the lesioned animals. In general, lesions resulted in cranial displacement of hyo-laryngeal structures, associated with modified and highly stereotyped tongue and hyoid kinematics. These changes affect structures that are critical in both sucking and airway protection. This suggests that a high level of coordination among several cranial nerves providing sensorimotor innervation for the entire oropharyngeal complex occurs in the brainstem, including sensory fields outside of the immediate functional area.
