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What is Functional Near-Infrared Spectroscopy?

Functional optical brain imaging is more commonly known as a scientific research technique called functional near-infrared spectroscopy (fNIRS). This technique is a type of functional neuroimaging technology that offers a relatively non-invasive, safe, portable, and low-cost method of indirect and direct monitoring of brain activity. By measuring changes in near-infrared light, it allows researchers to monitor blood flow in the front part of the brain. It is still a new technique, so it is not yet widely used in research, but it shows promising results in studies done to-date.

How a fNIRS sensor is worn.

A typical fNIRS sensorMore technically, it allows functional imaging of brain activity (or activation) through monitoring of blood oxygenation and blood volume in the pre-frontal cortex. It does this by measuring changes in the concentration of oxy- and deoxy-haemoglobin (Hb) as well as the changes in the redox state of cytochrome-c-oxidase (Cyt-Ox) by their different specific spectra in the near-infrared range between 700-1000 nm.

The functional near-infrared spectroscopy (fNIRS) sensor is attached to the subject’s forehead and can be monitored either connected directly to a computer, or a portable computing device that records the subject’s data as he or she engages in specific tasks. The data is recorded and then analyzed for changes in the blood flow or its oxygenation levels of the brain before, during, and after the task. Hypotheses can then be tested about how brain activity is being affected by certain tasks or behaviors.

A typical fNIRS sensor
What is Functional Near-Infrared Spectroscopy?

John M. Grohol, Psy.D.

Dr. John Grohol is the founder of Psych Central. He is an author, researcher, and expert in mental health online, and has been writing about online behavior, mental health and psychology issues since 1995. Dr. Grohol has a Master's degree and doctorate in clinical psychology from Nova Southeastern University. Dr. Grohol sits on the editorial board of the journal Computers in Human Behavior and is a founding board member of the Society for Participatory Medicine. You can learn more about Dr. John Grohol here.

APA Reference
Grohol, J. (2019). What is Functional Near-Infrared Spectroscopy?. Psych Central. Retrieved on December 2, 2020, from
Scientifically Reviewed
Last updated: 19 Jun 2019 (Originally: 17 May 2017)
Last reviewed: By a member of our scientific advisory board on 19 Jun 2019
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