1 Integration of the Reflex Pharyngeal Swallow into Rhythmic Oral Activity in a 2 Neurologically Intact Pig Model 3 4 5 Rebecca

42 Mammalian swallowing involves the coordinated and sequential activity of 43 many oropharyngeal muscles. Using synchronous electromyography and 44 videofluorography, we recorded the pattern of EMG activity for 12 muscles during 45 swallowing in neurologically intact suckling pigs. We tested the hypothesis that 46 this EMG pattern corresponded to the established pattern of activity for the 47 isolated, reflexive pharyngeal swallow of the decerebrate infant pig. The EMG 48 activity associated with the normal swallow had two components: (1) a staggered 49 pattern of single EMG bursts that were prominent in the stylohyoid, thyrohyoid, 50 cricothyroid and omohyoid muscles (2) double bursts of activity in some muscles, 51 including geniohyoid and genioglossus, with the same underlying periodicity as 52 suckling. Most of the staggered activity pattern, a linear sequence of progressively 53 delayed activities in different muscles, was not statistically different from that 54 previously found in the reflexive pharyngeal swallow of the decerebrate. However, 55 not all components of the linear sequence of the reflexive swallow were inserted 56 unchanged into the intact swallow. Some components appeared to be delayed or 57 advanced, bringing them into phase with the underlying rhythmic activity. The 58 difference between swallows of intact and of decerebrate animals was not solely 59 due to the presence of rhythmic activity in the former. The timing of some EMG 60 activities in intact animals also differed from the same activities in the few 61 decerebrates that exhibited rhythmic tongue and jaw activity. These results 62 suggest cerebral function influences the EMG pattern of the pharyngeal swallow, 63 which has traditionally been considered a purely reflex pattern. 64