Extracellular diffusion in laminar brain structures exemplified by hippocampus

► Stratification of brain structures profoundly affects extracellular diffusion. ► A generalized diffusion equation for inhomogeneous environments is derived. ► Numerical solution for layered structures is implemented. ► Volume fractions and diffusion permeabilities of hippocampal layers are quantified. ► Stratum pyramidale is shown to act as a diffusion barrier.