Fig. 4. Sixteen averaged bicoherence spectra are superimposed around the diagonal lines (f¹= f²), and means with SDs are shown.  Thin line , during 1% sevoflurane;  bold line , 2% sevoflurane;  gray line , 3% sevoflurane. SDs are shown as  perpendicular lines (n = 16). Sevo = sevoflurane.