Development of one-channel fNIRS system and physiological noise reduction in brain hemodynamic responses

Functional near-infrared spectroscopy (fNIRS) is an emerging non-invasive optical technique which can measure cortical brain activities. This study describes the development of one-channel fNIRS system designed for brain-computer interface (BCI), six subjects participate in the experiment, the concentration changes of oxy-hemoglobin (HbO₂) and deoxy-hemoglobin (Hb) during mental arithmetic task are measured. And physiological noise in hemodynamic responses are reduced based on empirical mode decomposition (EMD). EMD is a data-driven and adaptive algorithm for analyzing non-stationary data. This method decomposes the original data into a set of intrinsic mode functions (IMFs). Noise can be eliminated by selecting appropriate IMFs. Compared with conventional butterworth filter, EMD achieves a higher contrast to noise ratio (CNR) in physiological noise reduction.