Quantification of the cortical contribution to the NIRS signal over the motor cortex using concurrent NIRS-fMRI measurements

► Pial vasculature contaminates the NIRS signal. ► Concurrent NIRS-fMRI recordings enables estimation of the cortical signal contribution. ► 20% of the HbR signal and 75% of the HbO signal has cortical origins (finger tapping). ► HbT should be used rather than HbO or HbR to map cerebral activity with NIRS.