 Background: Close relationship exists between sleep slow wave SSW and the generation of spike wave in NREM-sleep. SSW are cortically generated oscillations alternating between excitatory depolarization Up-phase of the SSW and inhibitory hyperpolarization Down-phase of the SSW. It has been shown experimentally that with increasing synchrony of slow neuronal oscillations SSW turn into spike waves. Acoustic pulses applied in correspondence to the SSW Up-phase enhance the amplitude of the subsequent SSW. Conversely, tones delivered at the SSW Downphase have a disruptive effect on the following SSW. 