![]() Since main absorbers in the tissue within the NIR range are oxygenated (HbO2) and deoxygenated hemoglobin (Hb), fNIRS can provide information on hemodynamic changes related to cortical activity based on neurovascular coupling. The back scattered light from the tissue is captured by light detectors where the change in its attenuation carries information on the concentration of the absorbers within the tissue during the monitoring time. fNIRS is an optics-based method where tissue is irradiated by constant amplitude light in the near infrared (NIR) range (650–950nm) at two or more wavelengths through the skin. ![]() This is partially due to the fact that the technology can lend itself to safe, portable, comfortable, affordable, easy to engineer and apply designs allowing brain monitoring in various conditions, including Single-Task-Walking (STW) and Dual-Task-Walking the latter task imposes greater demands on the attention system and requires increased involvement of the prefrontal cortex. ε and age dependent DPF and filter cut-off frequencies at 0.14 and 0.08Hz including those designed to remove confounding effects of Mayer waves had caused some linear increases or decreases on the extracted Hb and HbO2 signals, those effects were minimal in task related comparisons and hence, the overall study outcomes.įunctional near infrared spectroscopy (fNIRS) is a noninvasive brain imaging method that is utilized in various research and clinical applications providing information on cognitive functioning in attention, memory, language, motor, sensorimotor and executive function domains under more realistic, everyday settings. In the current study, we re-analyzed our data and determined that although using different conversion parameters i.e. Using fNIRS, we have previously shown significant increases in oxygenation in the prefrontal cortex from Single-Task-Walking (STW) to Dual-task-Walking (DTW) conditions in older adults due to greater cognitive demands inherent in the latter condition. Variation in processing algorithms and parameters can cause differences in Hb and HbO2 extraction which can in turn change study outcomes. Different sets of conversion parameters dependent upon wavelength, chromophores, and age have been reported. Hemodynamic signal extraction using raw intensity measurements at multiple wavelengths based on MBLL usually involves apriori knowledge of certain conversion parameters such as molar extinction coefficients (ε) and differential path length factor (DPF). ![]() Various algorithms have been proposed for the elimination of artifacts from frequency selective filters to blind source separation methods. ![]() fNIRS signals can get contaminated by various noise sources of physiological and non-physiological origins. fNIRS data processing involves artifact removal and hemodynamic signal conversion using modified Beer-Lambert law (MBLL) to obtain Hb and HbO2, reliably. The technology uses light in the near infrared range (650–950nm) to track changes in oxygenated (HbO2) and deoxygenated hemoglobin (Hb) obtained from measured light intensity using light-tissue interaction principles. Functional near infrared spectroscopy (fNIRS) is a noninvasive optics-based neuroimaging modality successfully applied to real-life settings.
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