Fig. 2

Spectral analysis of EEG signals before and after the administration of s-ketamine. a, d Median spectrograms of EEG pre- and post-administration of saline or s-ketamine during sevoflurane anesthesia. b, e 2-min epochs for analyzing. Black lines represent the edge frequency. c, f The power spectra of 2-min EEG pre- and post-administration of saline and s-ketamine, respectively. g The changes of power at slow wave, delta wave, alpha wave and beta-gamma wave (from left to right) between saline and s-ketamine groups. The power of slow wave, delta and alpha bands decreased but beta-gamma waves increased after the administration of s-ketamine. h The changes of peak frequency at slow wave, delta wave, alpha wave and beta-gamma wave (from left to right) between saline and s-ketamine groups. The changes of peak frequency of slow wave, delta and beta-gamma in saline group were not different from that of s-ketamine group, but alpha wave increased significantly after the administration of s-ketamine. The changes of power and peak frequency were obtained by subtracting the pre-administration values from the post-administration values. Beta-gamma: the frequency band of beta and gamma. ^*P < 0.05, ^**P < 0.01, ^***P < 0.001 saline group vs. s-ketamine groups