Reliability and response assessment of brain responses in fNIRS

Background: Functional near-infrared spectroscopy (fNIRS) is a new noninvasive neuroimaging technology that detects both oxyhemoglobin hemodynamics (HbO) and deoxy-hemoglobin hemodynamics (HbR), but there is no assessment approach that emphasizes the merits of fNIRS. New method: Based on fNIRS, we established an indicator system named the Area-Under-Curve-based Indicator System (AUCIS) to estimate the effect reliability of brain responses. Evaluating the positive and negative responses for HbO and HbR can better explain, to some extent, the comprehensive physiological mechanism of oxygen delivery to and extraction in the brain. Moreover, we also established a reliability coefficient, named AUC’ α, to assess the robustness of within-subject condition effects. Results and Comparison: To validate the AUCIS, we used a simulation-based HRF signal and an open database and compared the performance with other general indicators. The AUCIS showed a greater relative sensitivity and robustness, which can be explained in terms of oxygen delivery and extraction based on the negative and positive responses of HbO and HbR.