Fig. 3.

Average $t$-values across all participants and channels calculated for various ${\tau }_p$ values for each signal and each task are indicated by the color scale. The optimal ${\tau }_p$ value, which gave the maximum $t$-value, was 6 s for the oxy-Hb signal in the NMT (naming task), 17 s for the deoxy-Hb signal in the NMT, 10 s for the oxy-Hb signal in the VFT (verbal fluency task), and 24 s for the deoxy-Hb signal in the VFT.