Figure 3. Treatment effects on parameters of spontaneous electroencephalogram activity before and after medication for all treatment groups. Left: Time course of the power in different frequency bands: delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), and beta (12–30 Hz). Right: time course of four frequency percentiles. Given are mean values and their standard errors for 1-min intervals. The most obvious effects were a marked increase in theta power after injection of 0.5 mg *symbol* kg-1ketamine and a decrease in alpha power. Corresponding to changes in theta activity, spectral edge (f95%) was significantly reduced. Although the mean median frequency (f50%) was significantly reduced immediately after ketamine injection, for subjects who showed low baseline alpha power, ketamine-induced theta activation sometimes resulted in an increase of the median frequency, even in periods in which the subjects were unresponsive.