Opposing modulation of cortical and corticospinal excitability across movement-related beta stages

Discrete voluntary movement depends on rapid changes in neural excitability across cortical and corticospinal circuits, yet how intrinsic movement-related neural states shape multi-level excitability remains unclear. Here, we combined individualized, state-targeted transcranial magnetic stimulation (TMS) with electroencephalography and electromyography recordings during visually cued finger movements to probe excitability across movement-related beta-band dynamics during two complementary experiments. Immediate transsynaptic cortical excitability closely tracked intrinsic beta dynamics, with attenuation of the second immediate TMS-evoked potential during beta desynchronization and recovery during the post-movement beta rebound. In contrast, corticospinal excitability showed the opposite pattern, with larger motor-evoked potentials during beta desynchronization and reduced responses during beta rebound. Together, these findings identify endogenous beta-state dynamics as a key regulator of movement-related cortical excitability and reveal a fundamental dissociation between how intrinsic brain activity tunes local cortical excitability and corticospinal output in humans.