I am finding that as I am trying to define the structures in the Neurolex, that I need something along the lines of "White matter structure" or perhaps "predominantly white matter structure", as that is technically more correct (a la Brain Info) to define just gross anatomical structures. Some of these are entire tracts, e.g., the mammillothalamic tract, while others are things like the internal capsule which are divisions that don't delineate entire white matter tracts or pathways. Rather, they contain parts of individual tracts and other pathways. The internal capsule is a segment along a larger "highway", that is, we can define the next part of the highway (the crus cerebri), the pontine white matter, the medullary pyramids. If we can set the CUMBO terms for these two types, we have accomplished a lot.