We present HemodynamicVR, a virtual reality headset combined with functional near-infrared spectroscopy (fNIRS). We believe that sensing brain activity will enable novel interactions in virtual reality. In this paper, we assess a user's cybersickness based on the change of their total hemoglobin concentration measured via an fNIRS device, and we try to mitigate that by changing the field of view (FOV) in real-time. In this experiment, participants experienced VR locomotion with an added variable FOV controlled by velocity changes and by fNIRS. The results suggest that fNIRS can detect cybersickness as registered by the qualitative SSQ test.