Fig. 9. Averaged bicoherence spectra of 10 series superimposed around the diagonal lines (B_1) and around the α frequency lines (B_2) in 2% sevoflurane. Means and SDs are shown as black bold lines and perpendicular lines , respectively (n = 10). Arrows indicate α and δ-θ peaks appearing around the diagonal lines and also indicate third peaks appearing in the bicoherence ridge along each α frequency line. α= bicoherence peak around α area; δ-θ= bicoherence peak around δ-θ area; third peak = third peak appeared in another heterogeneous pair, between α basal frequency and the double harmonic.