Functional Near-Infrared Spectroscopy for Brain Mapping

A 48-channel fNIRS MR-compatible device (OxyMon fNIRS, Artinis) was utilized in the present study for recording the variations in the concentration of oxy- and deoxyhemoglobin. The device is located in the National Brain Mapping Laboratory (NBML) and could transmit infrared (IR) radiation at 730 and 850 nm, and 10-Hz sampling frequency, which can penetrate the skull and assess the brain cortex. Additionally, the changes in the concentration of blood oxy- and deoxyhemoglobin were calculated based on Beer-Lambert's law (Delpy et al., 1988 (link); Obrig et al., 2000 (link); Toronov et al., 2000 (link); Boas et al., 2001 (link)). The results of the previous studies indicated that neuronal activity leads to consecutive changes in the concentrations of oxy- and deoxyhemoglobin. fNIRS signals were recorded from 24 channels involving 10 transmitters and 10 detectors located in the three different regions of the brain frontal cortex including ventrolateral (VLPFC), dorsolateral (DLPFC), and medial prefrontal cortex (MPFC). A 3-cm constant distance was considered between each transmitter and detector, which can evaluate the penetration depth of 1.5 cm. The arrangement of channels and their associated areas are provided in Figure 2.