Fig. 1

fNIRS channel arrangement. fNIRS optodes were distributed across two distinct cortical regions. A total of 6 light sources (red circles), 8 standard-separation detectors (blue circles), and 6 short-separation detectors (green circles) were utilized, where a source-detection pair (yellow lines) forms a channel. A standard source-detector distance of 30 mm was used, to yield an approximate light penetration depth of 30 mm, while short-separation detectors were positioned 8 mm from the light source to yield a shallow penetration depth. Channels C1-C8 covered primarily the bilateral medial and anterior prefrontal cortex (superior, middle, and inferior frontal gyri) and to a lesser extent, more lateral areas. Channels C9-C16 were positioned along the primary and secondary somatosensory cortex (pre- and postcentral gyri) on the right hemisphere. The sensitivity profiles for prefrontal and somatosensory channel arrangement for detecting CNS hemodynamics is represented on a logarithmic color scale (arbitrary units). Blue: 0 (minimum sensitivity); Red: 2 (maximum sensitivity)