Fig. 4From: Optimized electroencephalogram and functional near-infrared spectroscopy-based mental workload detection method for practical applicationsANOVA of each channel comparing four difficulty levels. The figure shows ANOVA results in four frequency bands. All data are processed by Z-score first and outliers are removed. The result was corrected by FDR. White represents P > 0.05, deep brown indicates P < 0.01, and light brown indicates 0.01 < P < 0.05Back to article page