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Imagent

functional Near Infrared Imaging System (fNIRS) Brain Imaging using Infrared Photons

The Principle

It has been known for more than 100 years that specific types of neurological deficits are induced by lesions to particular areas of the brain. The observational data accumulated in this past century indicate that the brain can be viewed as a complex information-processing center comprising structures specialized for different types of functions. Different areas work together to produce complex behavior that may be disrupted if the communication between areas is severed. In the past 20 years, cognitive psychologists and neuroscientists have increasingly converged their mutual observations towards a comprehensive theory of brain/mind function, this new discipline being named “cognitive neuroscience.” Non-invasive functional brain imaging techniques are instrumental in advancing the discipline, as they allow the researcher to derive measures of physiological activity of the human brain. Functional information, versus structural, derives from the slow (> 100 ms) and fast (
-1 -1 a = 0.1 cm and a scattering coefficient µ
s ' = 8 cm , the maximum optical penetration can be estimated to be about 1.5 cm when a detector is placed at 4 cm from the source. The penetration depth can be increased by increasing the distance between the source and the detector, although, eventually, the signal-to- noise ratio of the measurement deteriorates.