of activity, with the underlying cortical currents shifting over time to different regions across the cortex. In contrast, during non-REM sleep, TMS induced a much larger immediate local response that then terminated rapidly. Furthermore, the TMS-evoked potential was confined to the region of stimulation, and did not propagate to any other cortical region (Figure 6). These results thus supported the hypothesis that the loss of consciousness during sleep is associated with a breakdown in effective connectivity between different cortical regions. A recent follow-up study utilizing TMS demonstrated a similar breakdown in effective connectivity during the loss of consciousness induced by midazolam anesthesia (Ferrarelli et al., 2010).
