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As the most crucial organ of the human body that quintessentially defines humanity, the brain is still our greatest puzzle to solve. Medical doctors, neuroscientists, physiological scientists, and others have been trying to understand how its functions affect our actions, dating all the way back to the dark days of phrenology. In our study of the brain, the popular research is directed towards conscious thought, thinking, or the scientific term, cognition. In physical terms, the brain is separated into different areas of grey matter for different tasks, and like an electricity operator supplies a power grid with different levels of electricity on demand, regions of the brain gearing up for critical thought are saturated with fresh, oxygenated blood to boost performance: again a sign of an active cognitive state.

In modern scientific research, one of the popular means to measure this oxygenation is through Spectroscopymore specifically, a unique field called functional near infrared spectroscopy. How does fNIRS work in measuring human cognition? These measurements are performed with optical diodes and sensors measuring a near infrared wave pattern.

Dedicated fNIRS software displaying tissue oxygenation

A graphical display of oxygenation in the prefrontal cortex

Near infrared light is sent through the skull in a spectrum that can pass through bone and tissue, and the sensors record the plots of photons absorbed by tissue or reflected back.  Naturally with such a delicate subject such as the human brain, this process is both safe for the participant and painless.

The practical benefits of this spectroscopic measurement are numerouscontinuous and real time values on changes in hemoglobin levels in the prefrontal cortex (measured as oxyhemoglobin [Hb] and deoxygenated hemoglobin [HbO2]) as subjects perform different tasks, either in a stationary recording position or in a mobile experiment environment. fNIRS technology offers standalone and field-deployable technology able to determine localized brain activity. Modern recording tools such as the fNIR103M offer a wireless recording platform, so research subjects can react naturally in real-world situations outside of the lab environment while continuously recording spectroscopic data.

fNIRS is a popular signal to record simultaneously with other physiological signals such as heart rate, ECG, HRV, EMG, respiration, and more to get a clear picture of a subject’s physiological reactions. Application areas for this signal typically include pain assessment, geriatrics, attention, sports science, Human-Computer Interface, virtual reality, stress, workload assessment, and learning. Thousands of scholarly citations have been written featuring functional near-infrared spectroscopy, as studies visualize how the brain works through cognitive problems and processes. To further your physiological research, BIOPAC’s AcqKnowledge software can record multiple physiological signals at once and provide automated analysis tools for event related potentials and ensemble averaging. fNIRS easily integrates with other physiological and neurobehavioral methods of assessing brain activity, including eye tracking, pupil reflex, respiration, and electrodermal activity.

BIOPAC Systems, Inc. provides life science researchers and educators with data acquisition and analysis systems that inspire people and enable greater discovery about life. Visit us at We invite you to look at our recent and upcoming fNIRS webinars from BIOPAC. BIOPAC also offers a line of wired and wireless fNIRS imagers for research and education.

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