Kyle Thomas
BME PhD Defense Presentation

Date: 2025-08-15
Time: 10 AM – 11 AM
Location / Meeting Link: Whitehead Auditorium in Emory’s Whitehead Biomedical Building / https://emory.zoom.us/j/4531439090

Committee Members:
Sam Sober, PhD (Advisor); Megan Carey, PhD; Timothy Cope, PhD; Lena Ting, PhD; Chethan Pandarinath, PhD


Title: Motor unit control of mouse locomotion

Abstract:
Locomotion relies on neuromuscular circuits that produce rhythmic activity across the limbs and body. Motor neurons within the spinal cord innervate limb muscles, causing them to contract and generate the forces that moves the body. For movements as complex as locomotion, motor units, which consist of a single motor neuron and the muscle fibers it innervates, must be coordinated within and across muscles to not only move, but also to flexibly adjust locomotor rhythm. Although it is well established that motor units modulate the force output in muscles largely through their recruitment and firing rate, it is unclear how these firing patterns, both in individual motor units and in populations of motor units, are coordinated during dynamic movements. Using novel neurotechnology that allows for high-resolution investigation of the neuromuscular system, work presented in this thesis describes the coordination of motor units during locomotion in mice across different speeds. In Chapters 1 and 2, we introduce key concepts regarding the neuromuscular control of locomotion and review literature in the field. In Chapter 3, we identify how the firing rate and recruitment probability of individual motor units correlates with not only movement speed, but also specific kinematic features of each stride. Characterizing these results across different muscles in the mouse forelimb, we highlight how muscles with shared functions may be uniquely controlled by the nervous system. In Chapter 4, we use pair-wise analyses of motor units to determine how populations of motor units are recruited and de-recruited within muscles. Motor units were recruited but not de-recruited in a systematic order, and deviations from this order were correlated with stride-by-stride changes in locomotor behavior. Taken together, these results provide evidence on how the mouse neuromuscular system coordinates robust and flexible locomotor behavior.

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Georgia Institute of Technology and Emory University

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