Summary of α peaks in power and bicoherence spectra, shown as medians with 10th, 25th, 75th, and 90th percentiles in 45 cases. (A) α-Power peak; (B) α-bicoherence peak; (C) frequency at α-power peak; (D) frequency at α-bicoherence peak. *P < 0.05 for Wilcoxon signed-rank test.