FIGURE 1.

Schematic illustration of habenula connectivity with the social decision-making network (SDMN) in vertebrates. In mammals (A), the SDMN comprises the social behavior network (SBN) (1–7) and the mesolimbic reward structures (6–13), but some structures are shared by the SBN and the mesolimbic reward structures (6 and 7). In teleosts (B), each brain region that has been suggested to be homologous to the respective components of the mammalian SDMN is indicated by the corresponding number (shown in parentheses). In mammals, the habenula consists of the medial (MHb) and lateral (LHb) subnuclei, which receive direct (solid lines) or indirect (dotted lines) projection from the component of SDMN. In teleosts, the habenula consists of the dorsal (dHb) and ventral (vHb) subnuclei, which are homologous to mammalian MHb and LHb, respectively. Similar to mammals, there is connectivity between the habenula and teleostean SDMN. However, the detailed subnuclei-specific connectivity has not been precisely characterized in fish brain. The abbreviation of brain regions refers to Table 1.