Meeting Abstract
The pharyngeal swallow uses a series of bilateral muscle contractions to propel a bolus from the mouth into the esophagus. Due to the evolutionary history of vertebrates, the airway crosses the food pathway, and can become compromised during a swallow. This is especially problematic for mammals, which have a high metabolic activity, and therefore cannot stop breathing while feeding. Stimulation of the superior laryngeal nerve initiates a swallow, and unilateral lesion of this nerve usually causes the airway protection mechanisms to fail. This nerve, however, has multiple brainstem connections, including ones to the central pattern generator for swallowing, suggesting a role greater than just triggering the swallow. Thus a unilateral lesion could produce asymmetric activity in muscles involved with suckling and swallowing, even though these are mid-line or bilaterally synchronous activities. In contrast, activities such as locomotion normally have asymmetric muscle activations. To test this hypothesis, we examined activity via electromyography in the right and left mylohyoid, geniohyoid, digastric, and thyrohyoid in four pre-weaning infant pigs while they drank milk. We examined feeding activity before and after a surgical transection of the right superior laryngeal nerve. Preliminary results suggest that after nerve lesion, asymmetry increases between right and left muscles. None of these muscles are supplied by the superior laryngeal nerve, or even by the vagus nerve (CN X). This suggests that disruption of this sensory input influences the swallowing network, including muscles supplied by ansa cervicalis (C1-3), as well as muscles that are not part of swallowing per se, supplied by CN V3.
