Mathematical Biology Seminar Carter Johnson, University of Utah Wednesday, September 16, 2020 3:05pm via zoom Neuromechanical Mechanisms of Locomotion in C. elegans: Relative Roles of Neural and Mechanical Coupling Abstract: C. elegans is an ideal organism for studying brain-body-environment interactions, due to its well-described connectome, its amenability to optogenetic and mechanical manipulations, and its limited behavioral repertoire. Its simplest behavior is forward locomotion. While the motor circuit responsible for forward locomotion has been determined (White et al., 1986), the exact mechanisms by which neural and mechanical feedback produce coordinated locomotion are not well-understood. For instance, C. elegans is known to adapt its undulatory gait to fluid environments of different viscosities (Berri et al., 2009, Sznitman et al., 2010, Fang- Yen et al., 2010). Work by Boyle et al. (2012) was able to capture this phenomena by modeling the motor circuit effectively as a chain of coupled neuromechanical modules. Each module exhibits intrinsic oscillations, and active neural coupling and passive mechanical coupling through the body and environment coordinate activity of the modules. We develop a similar neuromechanical model that allows us to explore the relative roles of (passive) mechanical and (active) neural coupling in coordinating locomotion and uncover a mechanism that explains gait modulation in fluid environments of varying viscosities. The theory of weakly coupled oscillators is used to break apart the relative contributions of each form of coupling and to uncover possible mechanisms of coordination in the C. elegans motor circuit.