Fig. 4.

Optodes allocation, target ROI, and channels. A lattice arrangement of 18 pairs of optodes provided 54 channels to measure a whole head region. After fNRIS measurement and 3D digitizing of optode positions, the Brodmann area (BA) contribution rate at each channel of all participants from the digitized optode positions data was calculated. The target channels at the target ROIs defined by the 2×2 matrix square of the NIRS measurement area were selected referring to the distribution of the target BA contribution. The target BAs were the dorsolateral prefrontal cortex (DLPFC; BA46) for the modified serial number task and the somatosensory cortex (SC; BA7) for the SUMANU task. ROI, region of interest.