Functional near-infrared spectroscopy (fNIRS)

Functional near-infrared spectroscopy is a type of brain-computer interface using near-infrared light. Next to EEG (electroencephalography), fNIRS is one of the most used non-invasive techniques for detecting brain signals.
The spectrometer detects changes in oxy- and deoxyhemoglobin concentrations in the cortical regions. They are detected as changes of light intensity and are related to changes of hemoglobin concentrations through the modified BEER-Lambert law.
The signals can be measured only in the regions near the cortical surface.

A fNIRS sensor consists of an emitter, which emits light of a specific wavelength, and a detector; the two need to be placed 30 mm apart on subject's head during an experiment. Usually several emitters and detectors are placed, providing several channels of recorded data.

References

Wikipedia. (n.d.). Functional near-infrared spectroscopy Wikipedia. Retrieved 01.09.2023 from URL