Diffusion MRI relies greatly on the apparent diffusion coefficient as a key indicator of tissue microstructure, yet the way and the extent to which intracellular dynamics influence it remains elusive. In this work the role of cytoplasmic streaming induced by neuronal activity on apparent diffusion coefficient in neural cells was investigated. A hippocampal neuron was modeled and the effect of the forces generated by action potential streaming were numerically simulated. Coupling Navier-Stokes equations with elastic solid equations and action potential forces enabled us to obtain the generated intracellular flow which then was used in transport equations to calculate concentration of the diffusion propagtor and its variance over the computational domain. A significant increase of 27% in apparent diffusion coefficient was observed at action potential firing frequency of 200 Hertz. Furthermore, this enhancement increases quasi-linearly with frequency. This work demonstrates that the effect of action potential-and the subsequent generated intracellular flow-on apparent diffusion coefficient is non-negligible; therefore, disturbing action potential firing can result in a reduction in measured apparent diffusion coefficient values. These findings could improve the current understanding of apparent diffusion coefficient reduction under pathological conditions and lay a foundation for future studies on this topic.
Saboorian et al. (Mon,) studied this question.