Meeting Abstract

100.6  Wednesday, Jan. 7  Regional specialization in the mammalian sternohyoideus KONOW, N.**; THEXTON, A.; CROMPTON, A. W.; GERMAN, R. Z.; Johns Hopkins University, Physical Medicine and Rehabilitation; Kings College, Guy’s Campus; Museum of Comparative Zoology, Harvard University; Johns Hopkins University, Physical Medicine and Rehabilitation nkonow@jhmi.edu

The complex array of oropharyngeal muscles is critical to multiple behaviors in mammals. The sternohyoid is recruited during several behaviors, including respiration and vocalization, food acquisition (infantile suckling and adult biting), food processing and swallowing. Given its relatively simple architecture, we hypothesized that the mammalian sternohyoid would exhibit limited intra-muscular variation in EMG activity and recruitment patterns, and that variation in sternohyoid length dynamics would be restricted both within and among behaviors. Therefore, we investigated the level of intra-muscular variation in length-dynamics, measured using sonomicrometry, relative to the EMG of the sternohyoid in infant mini-pigs during suckling and swallowing. The sternohyoid behaved as a single unit during swallowing, which is an ancestral reflexive activity. However, regional differences in contraction-dynamics occurred during rhythmic suckling, indicating that one muscle section contracted isotonically while another section underwent eccentric contraction. Our results suggest that the mammalian sternohyoid contains unrecognized populations of regionally specialized motor units involved with the novel mammalian suckling behavior. We propose that this pool of variation is the historical legacy of this ancient muscle. Research funded by NIH DC03604 to RZG.