Corticothalamic communication for action coordination in a skilled motor behavior

The coordination of forelimb and orofacial movements to compose an ethological reach-to-consume behavior likely involves neural communication across brain regions. Leveraging wide-field imaging and photoinhibition to survey across the cortex, we identified a cortical network and a high-order motor area (the central region of the secondary motor cortex (MOs-c)), which coordinate action progression in a mouse reach-and-withdraw-to-drink (RWD) behavior. Electrophysiology and photoinhibition across multiple projection neuron types within the MOs-c revealed differential contributions of pyramidal tract and corticothalamic (CT^MOs) output channels to action progression and hand-mouth coordination. Notably, CT^MOs display sustained firing throughout RWD actions and selectively enhance RWD-relevant activity in postsynaptic thalamus neurons, which also contribute to action coordination. CT^MOs receive converging monosynaptic inputs from forelimb and orofacial sensorimotor areas and are reciprocally connected to thalamic neurons, which project back to the cortical network. Therefore, the motor cortex CT channel may selectively amplify the thalamic integration of cortical and subcortical sensorimotor streams to coordinate a skilled motor behavior.