The neuro subset of RO can be found at

For details, see:

D Osumi-Sutherland, S Reeve, CJ Mungall, F Neuhaus, A Ruttenberg, GSXE Jefferis, J Douglas Armstrong A strategy for building neuroanatomy ontologies Bioinformatics 28 (9), 1262-1269

Relations and their axioms (in OWL and CLIF) are summarised in the supplementary material for this paper