Fig 1.

Microscopic views (Luxol fast blue-periodic-acid-Schiff) at 2 magnifications of 40X (A–C) and 100X (B–D) showing healthy GM, with a few scattered bundles of myelin (blue) in the caudate nucleus (A and B) and islets of GM surrounded by numerous myelin sheets (blue) in the thalamus (C and D) of a subject who was not part of this study and who died from a non-neurologic disorder. B shows well-delineated, sparsely distributed WM bundles (large arrowheads) within the homogeneous cytoarchitecture of the caudate nucleus. D shows that myelinated fiber bundles occupy a large fraction of the thalamic complex, both between (large arrowheads) as well as within (small arrowheads) thalamic subnuclei (shown with dotted outlining), where they are interspersed with neuronal cell bodies, providing the necessary intra- and extrathalamic connectivity. It is evident that myelinated WM fibers are much more prevalent in the thalamus compared with the caudate nucleus, providing a plausible explanation for the finding of higher peak FA in the thalamus of healthy controls compared with that of their caudate nuclei.