Fast Diffusion fMRI (dfMRI) along the visual pathway closely tracks electrophysiological signals in the negative BOLD regime

The underlying sources of negative BOLD responses (NBRs) are still debated. We have recently shown that Positive BOLD response (PBR) to NBR transitions can be induced in the visual pathway by modulating the visual frequency of stimulation, reflecting neural activation/suppression, respectively. Here, we investigate how diffusion functional MRI (dfMRI) signals, which suffer less from vessel contamination, correspond to these activation and suppression regimes. Our results show that dfMRI signals are sharper and more sensitive to suppression induced at high visual stimulation frequencies. Furthermore, striking electrophysiology characteristics such as onsets and offset peaks are more prominent in the dfMRI signals.