Fig. 5. Electroencephalogram power spectra and spectrograms computed for each of four animals reveal a shift in peak power from delta to theta after administration of methylphenidate that is inhibited by droperidol. The top panel shows the 2-min windows used to compute power spectra before methylphenidate administration (red , “PRE”), and after methylphenidate administration (blue , “POST”). Spectrograms and power spectra computed from animals that received normal saline before methylphenidate (MPH). Power spectra show results of the Kolmogorov-Smirnov test for the 2-min periods before and after methylphenidate administration. At a 0.05 significance level (with Bonferroni correction) the Kolmogorov-Smirnov test rejects the null hypothesis at all frequencies except those marked with white squares. Statistically significant changes occurred at most frequencies between 0 and 10 Hz. The fourth animal moved during the time window used for the analysis, so motion artifact may account for the persistent high delta power observed after methylphenidate administration in this animal (A ). Spectrograms and power spectra computed from animals that received droperidol before methylphenidate (MPH). After droperidol, methylphenidate induced only statistically significant decreases in delta power (B ).