(from parent R03) Impaired chewing and swallowing as a result of orofacial or CNS injury or disease is a worldwide health problem that can impact quality of life and even be life-threatening. Current rehabilitation of such impairments has largely overlooked recent advances in neurorehabilitation of limb motor control, which may explain why many patients cannot regain normal chewing and swallowing. The oral primary motor cortex (oM1) is the main brain region involved in the generation and control of orofacial movements. However, detailed baseline 3D kinematics and electromyography (EMG) activity of aerodigestive and craniofacial structure as a whole which is to be compared to the pathological cases is lacking. Detailed characterization of modulations of local field potentials (LFPs) to gape types remains unclear. Furthermore, detailed kinematic and EMG encoding in single unit spiking activities for any orofacial behavior has not been performed. Lastly, relation between LFPs and muscle activities has not been explored except for beta oscillation and tongue muscles. Thus, to fill this knowledge gap, our specific aims are:
AIM 1 : To characterize and quantify 3D kinematics of aerodigestive and craniofacial structures and jaw and tongue EMG activities during natural feeding in awake rats. We will utilize our documented expertise with 3D high-speed videofluoroscopy and chronically implanted jaw/tongue EMG electrodes. We will: (a) characterize gape cycle types (e.g., chewing, swallowing) during feeding and how epiglottal and vocal fold open/closure are timed at each of the cycle types; and (b) perform dimension reduction techniques on both kinematics and EMGs to obtain a set of principal movements and EMG activities for each cycle type and transitions between cycle type.
AIM 2 : To relate the jaw/tongue EMG and 3D kinematics of aerodigestive and craniofacial structures to simultaneously record neural activities within multiple oM1 sites and layers in awake rats, and test if and how oM1 neural activity properties are related to tongue and jaw EMG and 3D kinematics of aerodigestive and craniofacial structures during feeding. We will utilize our documented expertise with chronically implanted microelectrode arrays that span horizontally and vertically into oM1 layers 2/3 (mainly cortico-cortico projections) and 5/6 (mainly output projections). We will then: (a) characterize how LFP profiles are related to types of gape cycles and their transitions between them; (b) characterize how kinematic- and EMG activities are encoded in single unit spiking activity of oM1; and (c) characterize cortico-muscular coherence between oM1 LFPs and jaw/tongue EMG activities for each gape type. This proposal will define a new 3D kinematic characterization of aerodigestive and craniofacial structures during feeding and novel oM1 neural mechanisms in terms of modulations of LFPs to gape cycles and single unit spiking activity encoding of kinematics and EMG based on layers. Better understanding of such mechanisms is needed to develop improved prevention and management of impaired motor functions resulting from oral injury, possibly by targeting oM1 neural processes.
The proposed research activities for Mr. Haxton, who is a member of nationally underrepresented minority, pertain to AIM 1 for the parent R03, to characterize and quantify 3D kinematics of aerodigestive and craniofacial structures and jaw and tongue EMG activities during natural feeding in awake rats. This supplement will specifically allow this candidate to receive training through a joint collaboration between two outstanding laboratories and increase his chance to be admitted to a medical school, and then develop into a physician. In addition to his previous training at Dr. Lever's lab, the proposed research experience will enable Mr. Haxton to not only gain advanced rodent surgical skills, but also novel, hands-on experience with CT neuroimaging and biplanar fluoroscopy and corresponding digital analysis methods for data extraction, and furthermore enhance the prospect for this promising applicant?s retention and advancement in the biomedical and health-related sciences.
