CORTICO-SUBCORTICAL DYNAMICS UNDERLYING ADAPTIVE LOCOMOTION

Locomotion is often conceptualised as an automatic movement, yet robust locomotion relies on flexible interactions between spinal and supraspinal regions. While central pattern generators have been extensively characterised, the role of supraspinal circuits in rapid corrective control remains elusive. Here, we address this gap by examining how interactions across cortical and subcortical sensorimotor regions change during skilled locomotion. We designed a task delivering rapid, unpredictable mechanical perturbations to head-fixed mice running on a large spherical treadmill using 12 evenly distributed actuators. Perturbations elicited a wide range of corrective behaviours, determined by actuator location and perturbation timing relative to the gait cycle. To probe cortico–basal contributions to skilled control, we recorded neural activity from limb-specific sensorimotor cortices, downstream basal ganglia projections, motor thalamic relay centres, and whole-body 3D kinematics. Perturbation direction could be decoded from both behaviour and neural activity across all recorded regions. However, peak decoding times differed across structures, with primary motor and somatosensory cortices preceding basal ganglia and thalamic regions. Perturbations selectively and transiently increased inter-region interaction strength compared to unperturbed running, with temporally shifted peaks suggesting directed information flow from primary motor to somatosensory cortex and onward to basal ganglia and thalamus.Notably, during blocks of perturbed trials, population activity in primary motor cortex—but not somatosensory cortex—underwent a persistent state-space shift relative to a ~10-minute pre-perturbation period. This shift persisted between perturbations, consistent with a change in control mode. Skilled locomotion therefore differentially engages cortical regions to support corrective responses requiring enhanced sensorimotor integration.