Method for obtaining near-infrared spectroscopy cerebral signal

A system for obtaining a near-infrared spectroscopy (fNIRS) cerebral signal in a subject, the system comprising:

• a device comprising a near-infrared emitter, a first near-infrared detector, and a second near-infrared detector, adapted for placing the near-infrared emitter and the first and second near-infrared detectors on a skin of a head of a subject, the first near-infrared detector being placed closer to the near-infrared emitter than the second near-infrared detector;
• and
• a computer configured to perform:
• during a baseline recording stage with the subject in resting-state, record near-infrared signals received from the near-infrared emitter in the first and second near-infrared detectors, the recorded signals comprising:
• a baseline deep-signal received by the second near-infrared detector, and
• a baseline shallow-signal received by the first near-infrared detector;
• calculate a scaling factor between amplitudes of the baseline deep-signal and the baseline shallow-signal with respect to a task that occurs at a given frequency;
• with the subject undergoing a cyclic cerebral stimulation according to an activity that occurs at the given frequency during a stimulation recording stage, record near-infrared signals received from the near-infrared emitter in the first and second near-infrared detectors, the recorded signals comprising:
• a shallow-signal received by the first near-infrared detector, and
• a deep-signal received by the second near-infrared detector;
• obtaining a cerebral signal at the given frequency during stimulation by:
• applying the scaling factor to the shallow-signal;
• and
• calculating the cerebral signal at the given frequency as a difference between the deep-signal and the scaled shallow-signal, at the given frequency.