Corticospinal neurons encode complex motor signals that are broadcast to dichotomous striatal circuits

Sensorimotor cortex controls movement in part through direct projections to the spinal cord. Here we show that these corticospinal neurons (CSNs) possess axon collaterals that innervate many supraspinal brain regions critical for motor control, most prominently the main input to the basal ganglia, the striatum. Corticospinal neurons that innervate the striatum form more synapses on D1-than D2-striatal projection neurons (SPNs). This biased innervation strategy corresponds to functionally distinct patterns of termination in spinal cord. CSNs are strongly driven during a striatum-dependent sequential forelimb behavior, and often represent high level movement features that are not linearly related to kinematic output. Copies of these activity patterns are relayed in a balanced fashion to both D1 and D2 projection pathways. These results reveal a circuit logic by which motor cortex corticospinal neurons relay both kinematic-related and unrelated signals to distinct striatal and spinal cord pathways, where postsynaptic connectivity ultimately dictates motor specificity. HighlightsO_LICorticospinal neurons send axon collaterals most abundantly to the striatum C_LIO_LIBiases in striatal innervation correspond to biases in spinal innervation C_LIO_LICSNs represent complex movement sequence information C_LIO_LICorollary motor sequence signals are relayed to both striatal projection pathways C_LI eTOC BlurbNelson, A. et al. detail the organization of corticospinal neurons and their coordinated cell type-specific targets in the dorsolateral striatum and spinal cord. Corticospinal neurons encode both kinematic-related and unrelated signals during motor sequences, and relay this information in a balanced fashion to dichotomous striatal pathways.