Recent work has shown that rTMS applied to motor cortex can produce changes in muscle motor evoked potentials lasting up to one hour. In an accompanying abstract, we show that rTMS of left motor cortex induces a localized potentiation of TMS-evoked cortical responses (Esser et al., SFN abstract 2005). Here we investigate whether rTMS induced potentiation performed during wakefulness produces lasting effects on EEG spontaneous activity recorded during subsequent sleep. Briefly, using a 60 channel TMS/EEG system with infrared stereotaxic positioning, we performed an rTMS potentiation protocol (1500 rTMS pulses, at 5 Hz, block design, 90% of motor threshold, left motor cortex hand area, 20 minutes session in the evening, n=4 subjects). TMS test stimuli showed an increase in the magnitude of cortical responses (101.1±23.9%) for a cluster of electrodes located slightly caudal and lateral to the site of stimulation. Immediately after the rTMS session, subjects were reclined and allowed to sleep while the EEG was...