Fig. 4

Representative time course of a spectrogram and bicoherence spectrum of a patient under propofol anesthesia supplemented with Dex. A Frontal cortical time-frequency spectrogram of the Fp1 channel during anesthesia. B Frontal cortical bicoherence spectrum during anesthesia. C Bicoherence 5 min before injection (left) and 10 min after injection (right) of Dex for all pairs of frequencies. D Frontal power spectra 5 min before (blue line) and 10 min after (red line) Dex injection. Note that α peak power and frequency decreased from the former to the latter time period. E Diagonal bicoherence of 5 min before (blue line) and 10 min after (red line) Dex injection. Note that the α bicoherence peak, α peak frequency, and slow θ peak frequency decreased while the slow θ bicoherence peak increased from the former period to the latter period