The shape, movement, and signals of active sensors: Modeling the biomechanics of deformable orofacial organs

Project 2. Abstract
The shape, movement, and signals of active sensors: Modeling the neuronal control and biomechanics
of deformable orofacial organs (Golomb as lead; all PIs contribute)
This Project addresses the dynamics of the neuronal circuits and their associated motor plants that underlie
different orofacial motor actions. We focus on two actions: whisking, driven by the vibrissa system, and licking,
driven by the lingual system. The proposed studies on the vibrissa system build on the relative plethora of
information on this orofacial action, as well as includes new data. In contrast, the proposed studies on the licking
system make extensive use of new data that is gathered in the Team experimental projects.
Models of each system include neurological centers, i.e., sensory, motor, premotor, and pre2motor nuclei
and ganglia, and biomechanical elements, i.e., the vibrissae, its mystacial pad, and the tongue. We will use
theoretical and computational techniques, together with new experiments, to describe how motor actions emerge
from these centers and elements. We further explain how active feedback alters motor activity during active
sensing. For the case of the tongue, we model two strong nonlinearities:the 1:n and n:m entrainment of breathing
with licking and the potnetial loss of entrainment of the tongue and jaw by breathing as the animal chews.
In Aims 1 and 2 will complete our analysis of the interaction between the vibrissae and the motor plant. Our
preliminary results show that a vibrissa functions as an elastic beam for distal objects and as a rigid body for
proximal objects. Using data from Project 1 to build a model that predicts spikes and object location from vibrissa
touch, we further investigate how ascending low-level inputs via the brainstem loop together with descending
high-level inputs control motor activity during behavior. Aims 3 and 4 are related to the tongue. We will construct
and analyze hydrostatic models of the tongue, including intrinsic and extrinsic muscles as well as vascularization,
that will describe changes in the shape of the tongue in responses to motor commands in foraging and in
consumption; these yield predictions for Project 5. In Aim 4, we further define how brainstem nuclei generate the
licking rhythm and its amplitude and how they are entrained by breathing oscillators. This study is carried out
interactively with experimental groups through Projects 1, 3, and 4.