Fig. 8.

Subject variances of systemic noise reduction in (a) ${\mathrm{O}}_2\mathrm{Hb}$ and (b) HHb signals neglecting the task effect in four channel regions: postcentral, premotor, temporal, and prefrontal cortices performed by ear-GLM denoising (black-filled boxplot), finger-GLM denoising (black-void boxplot), dual peripheral-GLM denoising (red-filled boxplot), and PCA 95 (red-void boxplot) – $p<0.001$^(***), $p<0.01$^(**), $p<0.05$^(*) for ANOVA and post-hoc Tukey–Kramer test. Because of low correlations between prefrontal and peripheral signals in HHb parameter, HHb signals were mostly not denoised. Therefore, the performance of peripheral-GLM denoising in HHb signal was significantly lower than PCA 95.