Corticospinal excitability in human sleep as assessed by transcranial magnetic stimulation.

The excitability of the corticospinal system was studied in 23 healthy subjects in sleep stages NREM2, NREM4, REM, and wakefulness using transcranial magnetic stimulation. Assessment of motor thresholds, stimulus-response curves, and latencies of motor evoked potentials shows activation of the fast-conducting corticospinal fibers in all sleep stages and a neuronal recruitment pattern similar to wakefulness, however, at a lower level of excitability and with significant differences between sleep stages.