title: Brain teaser.
mesh_terms: D002540:Cerebral Cortex / Q000033:anatomy & histology*; D003337:Corpus Callosum / Q000033:anatomy & histology*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*