SOME PROPERTIES OF CORTICALLY-EVOKED SWALLOWING AND CHEWING IN RABBITS

Under controlled ether anesthesia, the rostral half of the rabbit's brain was explored with repititive electrical pulses of various parameters to elicit rhythmic movements of swallowing and chewing. The features of the cortical areas and the modes of the two motor responses were compared. The effects of reflex stimulation to the oropharyngeal structures on these responses were also studied. 1. (1) A narrow cortical motor area for swallowing and a relatively wide area for chewing exist, largely overlapping, on the anterolateral surface. Both are irregular in shape and non-concentric. 2. (2) Stimulation of wider ranges both in intensity and frequency produced rhythmic chewing; however those of prominently narrow stimulus ranges produced rhythmic swallowing. An 'optimal frequency' between 30 and 50/sec was found for both responses. 3. (3) Cathodal stimulation was more effective in producing both swallowing and chewing than a anodal, and chewing was the more redily elicitable of the two responses. 4. (4) With deepening anesthesia, the territory of cortical motor areas shrank and the responses became feeber (elevation of threshold, decrease in rate of chewing and swallowing, prolonged latency). Swallowing was more susceptible to such depression than was chewing. 5. (5) Both the swallowing and chewing responses were facilitated by bilateral cortical stimulation, and the separation of the cerebral hemisphere by midline splitting left this effect unchanged. 6. (6) Weak or moderate intensity of stimulation to the superior laryngeal nerve facilitated the elicitation of the cortically-induced swallowing. The stronger stimulation, however, markedly suppressed chewing. © 1969.