Fig. 5

Coherence analysis between the awake period and the period during etomidate-induced LOC. a The coherence analysis of the awake period (n = 20) showed the coherence spectrum in terms of the slow wave (< 1.0 Hz), delta wave (1.0–4.0 Hz), and alpha wave (8.0–13.0 Hz). b The coherence analysis during etomidate-induced LOC (n = 20) shows the coherence spectra in terms of the delta wave (1.0–4.0 Hz), theta wave (4.0–8.0 Hz), and the alpha wave (8.0–13.0 Hz). During the awake period, the coherence of slow waves (< 1.0 Hz) was decreased. c The coherence spectra of the awake period and the period during induced LOC. The alpha wave (8.0–13.0 Hz) coherence is similar in both periods. However, the delta wave (1.0–4.0 Hz) during etomidate-induced LOC was more coherent than during the awake period (1.86–3.17 Hz, two-group test for coherence, p < 0.001). Median coherence is presented with 95 % jackknife CIs. Horizontal solid black lines represent frequency ranges at which there was significant difference. The bandpass filter allows frequency components to pass within a certain frequency range but attenuates the frequency components in other ranges to a very low level rather than cutting off frequencies outside the range at a certain frequency point; therefore, at 40 Hz, the graph shows that the coherence is uniform and rising