An increase in cortical excitability with no change in spinal excitability during motor imagery.

During motor imagery, to estimate changes in excitability of flexor carpi radialis muscle motoneurons of the spinal and cortical levels, electrical stimuli for recording H-reflex and transcranial magnetic stimulation (TMS) for recording motor evoked potentials (MEPs) were used. In the absence of movement or detectable EMG activity during motor imagery, there was an increase in cortical excitability with no change in spinal excitability.