Final Report Summary - MOTOR CIRCUITS (Neuronal circuits controlling motor behavior)
This project was aimed at the analysis of the neuronal circuits involved in the regulation of movement, a behavior representing the ultimate output of nearly all nervous system activity. Studying the mouse motor output system has allowed the analysis of neuronal circuit connectivity at an exquisite degree of specificity. The aim of this research project was to acquire information on the general principles guiding the acquisition, maintenance and developmental plasticity of neuronal connectivity between premotor neurons and subpopulations of motor neurons. Owing to the anatomical arrangement of motor neuron pools innervating individual muscles, we were able to combine genetic, anatomical and physiological analysis of synaptic specificity with a direct link to a behavioral output. In particular the application of novel viral circuit tracing technology revealing directly connected premotor neurons was instrumental to this project. Our project has elucidated the anatomical connectome of the motor output system in the spinal cord as well as the principles governing the specificity with which motor circuits assemble. We found that premotor neurons in the spinal cord and at supraspinal levels connect with a high degree of specificity and prefigure behavioral function. These findings include the organization of the neuronal network involved in the regulation of intralimb coordination patterns such as extension-flexion and left-right alternation, as well as more complicated motor programs at the core of regulating complex forelimb movement. In summary, this project provided an important contribution to neuroscience by generating insight into principles of circuit organization and function of the motor system.