part of part of dorsal tegmental nucleus regional part of brain dorsal tegmental nucleus pars dorsalis According to Hayakawa and Zuo (1983), the TDD cannot be clearly identified in the tree shrew or in human dorsal tegmental nucleus pars dorsalis UBERON:0014568 NLXANAT:20090407 dorsal tegmental nucleus of Gudden pars dorsalis Part of dorsal tegmental nucleus characterized by round, small cells that are lightly stained in Nissl preparations.