Spinal circuits for kinematic adaptation
1 University Hospital Cologne
2 Research Centre Jülich
Animals’ ability to execute and adapt movements relies on neural networks in the spinal cord that regulate the rhythm and pattern of muscle contractions. Neuronal dysfunctions within these circuits, resulting from physiological or pathological processes, affect postural stability and resilience of motor behavior to external perturbations. To assess the biomechanical strategies adopted by mice to execute postural-demanding motor tasks, we reconstructed 2D kinematics in mice challenged to run on a treadmill and cross increasingly narrower beams. The joint coordinates in markerless mice were tracked using DeepLabCut, and analyzed using the Python-based GUIs, AutoGaitA, that we developed. We observed typical kinematic adaptation signatures, with mice lowering their center of mass, shortening their stride, reducing their angular and joint velocities and changing their intralimb and interlimb coordination in a task-specific manner. PCA analysis revealed specific clusters defined by the distinctive kinematic features that mice adopt at certain treadmill speeds or on individual beams (25, 12 and 5 mm). By comparing 3-, 9- and 24-month-old mice, we observed an age-dependent increase in number of footslips and a shortening of the stride length. Next, we addressed how manipulating the activity of ventral premotor neurons affects the ability of mice to execute and adapt their coordination to the different tasks. Ablation of spinal V1, V2a and V2b neurons caused mice to slip more on the narrower beams and significantly changed their baseline limb kinematics and their ability to adapt their body coordination to tasks with higher demands of postural stability.