The NIFRS allows indirect measurement of neural activity by detecting relative changes in local blood concentrations of oxyhemoglobin (oxyHb) and deoxy-hemoglobin (deoxyHb). This non-invasive measurement is made using near infrared light emitter-detector pairs (channels or optodes) placed on the surface of the skull, allowing the absorption of this light by the blood chromophores to be evaluated. Two wavelengths are used, one more sensitive to deoxyHb and the other to oxyHb. The measurement only concerns external cortical areas. The Cerco is equipped with a NIRScout 8-source/8-detector system that can be used in humans to measure brain activity throughout the cortex.