Neural populations in the dorsal and ventral cervical spinal cord share temporal dynamics during reach
Neural population dynamics provide a popular framework for studying motor cortex function. However, whether such dynamics reflect stage-specific computations or are shared across the input and output stages of a sensorimotor circuit is unknown. In the spinal cord, afferent inputs and motor outputs are segregated by anatomical depth. Here we developed depth-resolved Neuropixels recordings from the rat cervical spinal cord during targeted reaching behavior. Across our recordings, population activity was low-dimensional and organized into transient, rotational and target-specific dynamical motifs. Despite differences in single-neuron activity by depth, dorsal and ventral populations expressed nearly identical dynamics across targets and animals. The dominant target-invariant component was strikingly synchronized across depths, whereas other components, including the target-specific component, showed condition-dependent ventral-to-dorsal delays with timing consistent with movement-related feedback. Thus, cervical spinal population dynamics span sensory and motor territories, and may reflect shared coordination of activity rather than purely state-specific local processing.