Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical imaging technique that measures changes in hemoglobin (Hb) concentrations within the brain by means of the characteristic absorption spectra of Hb in the near-infrared range. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical imaging technique that measures changes in hemoglobin (Hb) concentrations within the brain by means of the characteristic absorption spectra of Hb in the near-infrared range. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical imaging technique that measures changes in hemoglobin (Hb) concentrations within the brain by means of the characteristic absorption spectra of Hb in the near-infrared range. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical imaging technique that measures changes in hemoglobin (Hb) concentrations within the brain by means of the characteristic absorption spectra of Hb in the near-infrared range. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical imaging technique that measures changes in hemoglobin (Hb) concentrations within the brain by means of the characteristic absorption spectra of Hb in the near-infrared range. Functional near-infrared spectroscopy (fNIRS) is a noninvasive optical imaging technique that measures changes in hemoglobin (Hb) concentrations within the brain by means of the characteristic absorption spectra of Hb in the near-infrared range.