Dynamic engagement of the motor cortex in controlling movement

Neural circuits do not contribute equally or continuously to behavior. In mice, the motor cortex can be essential or dispensable for movement in different contexts, but how it is dynamically recruited as behavioral demands evolve remains unclear. Here, we demonstrate that motor cortical involvement in movement exhibits rapid, discrete state transitions even during movements that otherwise appear continuous. While robust and reproducible across animals, the timing and presence of these state transitions are highly sensitive to task structure. We find that motor cortical engagement is sustained under conditions of sensorimotor uncertainty and dissipates rapidly when sensorimotor contingencies are resolved and actions and outcomes thus become predictable. These findings reveal a previously unrecognized layer of fast-timescale flexibility in the neural control of movement and offer a conceptual framework for understanding how cortical circuits dynamically govern behavior as demands evolve.