[TA] diffusely arranged cell groups located in the posterior and more medial area of the tegmentum of the mesencephalon. These nuclei are: cuneiform nucleus [TA] (nucleus cuneiformis [TA]), subcuneiform nucleus [TA] (nucleus subcuneiformis [TA]), parapeduncular nucleus [TA] (nucleus parapeduncularis [TA]), and the pedunculopontine tegmental nucleus [TA] (nucleus tegmentalis pedunculopontinus [TA]). This latter nucleus can be divided into a compact part [TA] or compact subnucleus [TAalt] (pars compacta [TA]) and a dissipated part [TA] or dissipated subnucleus [TAalt] (pars dissipata [TA]). SYN: nuclei reticulares mesencephali [TA].