Injury compensation reveals implicit goals that guide locomotor coordination
Bauman, Jay Morris
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Locomotion persists despite changes in external and internal circumstances. Motor responses to gait impairment exhibit commonalities across various taxa and types of injury, yet we lack a systematic understanding of compensation strategies. The objective of this dissertation is to uncover principles governing implicit goals within the control of locomotion. I propose that coordination of injured locomotion will demonstrate that these goals follow a hierarchical organization of the neuromuscular system. Accurate quantification of gait deficits in rodents demands sophisticated measurement techniques. I utilize X-ray technology to examine intralimb and interlimb coordination after unilateral injury in rats. My findings indicate that compensation to injury involves the coordination of lower-order motor elements to preserve the pre-injury behaviors of higher-order elements. Specifically I present evidence that preservation of limb angle and limb length are critical task goals that transcend injury states and afferent sensory feedback conditions. Broadening my investigation to include interlimb coordination revealed that task goals may change to satisfy the goals of a higher hierarchical level. This work is a necessary precursor to study locomotor coordination and injury compensation in more complex rodent injury models such as self-reinnervation, sciatic nerve, and spinal cord injury. These results could also translate to clinical gait rehabilitation through future protocols that address motor patterns of the entire limb over the behavior of individual joints.