Ascending activating systems to the ventral telencephalon in the adult zebrafish brain (modified from Wullimann and Mueller, 2004; permission pending from Wiley-Liss, Inc.). Double-labeling studies identified the posterior tuberculum (PT) to dorsal nucleus of the ventral telencephalon (Vd) projection, proposed as the homologous meso-striatal pathway in mammals. Cholinergic (superior reticular), serotonergic (superior raphe), and histaminergic (caudal hypothalamic) nuclei require neurochemical confirmation. Ha, habenula; TL, torus longitudinalis; Vs, supracommisural nucleus; Vv ventral nucleus of the ventral telencephalon.