What can a rat tell about physics beyond Standard Model: Exchange or structural disorder?
AUTHORS: Jelescu I, Novikov DS
ISMRM & SMRT Annual Meeting, : , Online, May 2021
One fundamental challenge in brain microstructure is to establish the biophysical origin of effects beyond the “Standard Model” (SM) picture of non-exchanging Gaussian compartments. The intra-compartmental structural disorder competes with inter-compartmental water exchange. Here we show that in rats, the exchange dominates, and offer the picture of diffusion time effectively filtering out the contribution of unmyelinated axons with stronger dispersion. At long times, only the myelinated (non-exchanging) axons contribute to the intra-axonal SM compartment, and the rest is attributed to extra-axonal space.