Identifying brainstem oscillators and other low-level mechanisms controlling tongue and jaw movements

Abstract- Project 3 Identifying brainstem oscillators and other low-level mechanisms controlling tongue and jaw movements All vertebrate species depend on feeding for survival. Like breathing, feeding behaviors such as licking and chewing involve rhythmic actions that are thought to be generated by central oscillators located in the brainstem. However, the anatomical locations and the identity of feeding oscillator(s) remain poorly defined. We previously successfully delineated the rodent whisking oscillator at the molecular, anatomical, electrophysiological, functional, and mechanical levels. With all the techniques required to comprehensively investigate brainstem circuits in vivo during orofacial behaviors fully established, here we will explore the low-level neural mechanisms controlling feeding, especially licking, movements. Based on exciting preliminary studies, we will test the hypothesis that separate but coordinated neurons/circuits in the brainstem control different aspects of feeding including rhythmicity, amplitude/direction, and tongue shape. The goals of Project 3 are: (1) to molecularly, physiologically, and functionally delineate the brainstem premotor licking oscillator and amplitude controlling neurons; (2) to determine the interactions of premotor licking oscillator and amplitude controlling neurons during licking vs chewing behaviors; (3) to reveal the neural mechanisms involved in switching the modes of tongue/jaw movement patterns during licking vs chewing; and (4) to determine the function of intralingual parasympathetic neurons in regulating tongue shape and physiology. Results from Project 3 will generate experimental data for models in Project 2, and also test predictions derived from Projects 1 and 2. Project 3 will also provide the key brainstem substrates to dissect how descending control signals interact with brainstem nodes to drive flexible orofacial behaviors in Projects 1, 4, and 5.