A study on estimation of reaction and reaction part of brain by NIRS

Abstract

Functional near-infrared spectroscopy (fNIRS) is a useful approach for monitoring changes in the oxygenated and the deoxygenated hemoglobin (Hb) concentration of cerebral blood flow. When the brain is activated, oxygen is supplied to capillaries and the increase of oxygenated Hb and the decrease of deoxygenated Hb are observed. During the measurements, physiological fluctuations sometimes cause parallel changes in the oxygenated and deoxygenated Hb concentrations and falsely recognized as brain activity. Thus, we propose an analysis method using the time variation of the correlation coefficient for extracting the characteristics of Hb concentration of brain activity. We use two kinds of indicators. One is a correlation coefficient of the oxygenated Hb concentration between measured channels and the other one is a correlation coefficient of oxygenated and deoxygenated Hb concentration within the channel. We applied this method to the measurement with short-term memory tasks in the forehead using a 16 channel system.