An embodiment includes a functional near infrared (fNIR) system comprising: first, second, and third light emitting diodes (LED) and a photo detector； and at least one storage medium having instructions stored thereon for causing the system to: (a) emit photo energy at first, second, and third wavelengths from the first, second, and third LEDs during first and second time periods, (b) determine first, second, and third optical density changes and changes in first and second chromophore concentrations based on the emitted photo energy； and (c) determine and fit first, second, and third absorption values to a first absorption spectra curve based on the determined changes in first and second chromophore concentrations. Other embodiments are described herein.
