Positioning of probe sets. The positions of the emitters (red dots) and the detectors (blue dots) are illustrated over the left and right hemisphere. The channels between the optodes are consecutively numbered. T3, T4, Fp1 and Fp2 are standard electroencephalography points that mark the positions of the detectors between channel 1 and 2 on the left side and channel 3 and 4 on the right side. (PPT 208 kb)