We present results for frequency domain (FD) functional Near Infrared Spectroscopy (fNIRS), where signals from the haemodynamic changes due to focal activations are detected using FD data as collected during a standard retinotopy visual stimulus paradigm. The FD system utilizes radio frequency modulated light to measure phase shift, as well as intensity attenuation, allowing the utilization of two sets of complimentary data for brain activity detection. The information content from measurements of both amplitude and phase, afforded by FD-fNIRS are presented and it is shown that utilization of phase measurement contains unique information regarding both focal activation as well as systematic responses, which could lead to signal suppression from the superficial tissues.

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Matthaios Doulgerakis, Adam Eggebrecht, and Hamid Dehghani, "Information rich phase content of frequency domain functional Near Infrared Spectroscopy," Proc. SPIE 10865, Neural Imaging and Sensing 2019, 108650C (Presented at SPIE BiOS: February 04, 2019; Published: 1 March 2019); https://doi.org/10.1117/12.2505874.