Indirect measurement of brain activation using fNIRS

Functional near infrared spectroscopy (fNIRS) is an emerging non-invasive brain imaging technique based on estimation of blood chromosomes. The change in the concentration of oxy-hemoglobin (HbO) and de-oxy hemoglobin (HbR) gives indirect measure of brain activation. fNIRS measures the change in HbO and HbR depending on the absorption of near infrared (NIR) light. It uses the NIR light of two wave lengths, 760 nm and 830 nm. NIRS is a newly developed neuro imaging modality with high temporal resolution. NIRS systems have great potential for brain computer interface due to its low cost, portability and safety. The scalp remains intact throughout the experiment. In this study we present a method for estimation of brain activation by using fNIRS data collected during arithmetic task. The general linear model has been used in this study with predicted hemodynamic response function, its derivatives and physiological noises as regressors. The normalized least mean square (NLMS) algorithm has been used for estimation of activity strength parameters in the model recursively. A one way t-test has been performed for detection of brain activation at different channels.