Aalto University and University of Wisconsin
EEG responses evoked by transcranial magnetic stimulation during NREM sleep when subjects dreamt (red line) and did not dream (blue line). When subjects did not dream, 200 milliseconds after the stimulation, a strong deflection was visible in their EEG. This type of response is typical of cortical networks that are in a so-called bistable state in which after initial activation their activity resumes stochastically. The black and grey lines show statistically significant differences between the conditions. The responses visible on the right have been averaged over the channels specified with dashed lines.