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 for analyzing brain activities. However, the change includes the blood volume changes caused by the movement of the head position. The changes were superimposed on the changes in cerebral blood flow and falsely recognize it brain activity. For detecting the blood volume change, We propose an analysis method of focusing on the cross-correlation coefficient of the oxygenated and the deoxygenated Hb concentration.16-channel optical encephalography (Model OEG-16, Spectratech) was used for measurement in the forehead. A 20-year-old male-subject participated in the experiments. We applied pressure on the external jugular vein to produce blood volume change. During applying the pressure, both the oxygenated and the deoxygenated Hb concentration were increased in 11 of 16 channels. In the relevant channels, the correlation coefficient during the task period was took positive value (greater than 0.8), thus the correlation coefficient can be used for detecting the blood volume change.
