Fig. 2

Time-frequency analysis of EEG data between the awake period and etomidate-induced LOC. a During the awake period before induction of etomidate (n = 20), slow-wave (< 1.0 Hz) and delta-wave (1.0–4.0 Hz) oscillations were mainly present. b Etomidate-induced LOC (n = 20) yielded an increase in the power of slow waves (< 1.0 Hz), delta waves (1.0–4.0 Hz), theta waves (4.0–8.0 Hz), and alpha waves (8.0–13.0 Hz). c Spectrograms of the awake period. Compared with those during the awake period, the powers of the slow wave (< 1.0 Hz), delta wave (1.0–4.0 Hz), theta wave (4.0–8.0 Hz), and alpha wave (8.0–13.0 Hz) during the etomidate-induced LOC were significantly increased (C: 0–22.97 Hz, 27.28–40.00 Hz; p < 0.001, two-group test for spectra). Median spectra presented with 95 % jackknife CIs. Horizontal solid black lines represent the frequency ranges at which there were significant differences