In diffusion MRI, the use of very high b-value remains very challenging. In this study, we scanned 9 volunteers with a protocol of dMRI sequences using b values from 1000 to 5000 s/mm². We compared cortical surface map of myelin (T1wi/T2wi) to maps of mean diffusivity (MD) computed from each b value. As opposed to b1000 s/mm², MD maps from b3000 and b5000 inversely mirrored the myelin maps. With increasing b-values, multiple regression models confirmed an increasing negative association between myelin and MD. The MD obtained with high b-value is sensitive to subtle cellular variations such as the cortical myeloarchitecture.