Functional NIR Spectroscopy (fNIRS)

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NIRS is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (from about 700 nm to 2500 nm). Functional Near-Infrared Spectroscopy (fNIRS), is the use of NIRS for the purpose of functional neuroimaging. Using fNIR, brain activity is measured through hemodynamic responses associated with neuron behaviour. There is no sensation of any kind from the infrared light, and it is not harmful.

How does NIRS work ?

NIR spectrum light takes advantage of the optical window in which skin, tissue, and bone are mostly transparent to NIR light in the spectrum of 700-900 nm, while haemoglobin (Hb) and deoxygenated-haemoglobin (deoxy-Hb) are stronger absorbers of light. Differences in the absorption spectra of deoxy-Hb and oxy-Hb allow the measurement of relative changes in haemoglobin concentration through the use of light attenuation at multiple wavelengths. Typically the light emitter and detector are placed ipsilaterally on the subjects skull so recorded measurements are due to back-scattered (reflected) light following elliptical pathways. The fNIRS sensor is attached to the subject’s forehead and data can be recorded as he or she engages in specific task.


What is NIRS used for ?

fNIRS allows researchers to quantitatively assess brain functions—such as attention, memory, planning, and problem solving—while individuals perform cognitive tasks. It can also monitor cognitive state of the subject in natural environments. Some studies reported use of fNIR device in Aging research and also it has been successfully implemented as a control signal for Brain Computer Interfacing (BCI) systems.