Figure 4. Correlation between duration of unconsciousness (above) or pain reduction (below) and pharmacologic-induced changes in parameters of spontaneous and evoked electroencephalogram after application of 0.25 mg *symbol* kg-1(gray circles) and 0.50 mg *symbol* kg-1ketamine (black circles) in samples of 10 healthy subjects. During the time in which the theta power of the spontaneous electroencephalogram exceeded 20% of the corresponding premedication level, all subjects were unconsciousness. The ketamine-induced changes in the amplitude of the late SEP-component N150-P250were not correlated with “time of unresponsiveness” but with “pain reduction.”