Fig. 2.

Group spectrograms show canonical low frequency oscillations in the anaesthetised brain. Spectrograms measured from F3 combined over all 27 subjects. Spectra are computed for the last 2 h of isoflurane administration (starting 1 h into the administration). (a) The mean spectrogram computed over all subjects shows consistent power over all frequencies for the duration of anaesthetic exposure after equilibration. (b) The median spectrogram computed over all subjects shows similar results to the mean spectrogram. Both ways of combining the data across subjects show the well-known slow oscillations in the EEG under anaesthesia.