Figure 2.

Afferent and efferent connections of the habenula. The MHb, LHb, and pineal body (PB) are collectively called the epithalamus. The MHb receives inputs mainly from the supracommissural septum (S) and sends outputs to the interpeduncular nucleus (IP). The LHb receives inputs mainly from the basal ganglia and limbic regions and sends outputs to the brain structures containing DA neurons and serotonin neurons. Afferent and efferent connections of the habenula are conveyed by the stria medullaris (sm) and fasciculus retroflexus (fr), respectively. Green and blue lines indicate the axonal connections associated with the MHb and LHb, respectively; black lines are associated with both. The thickness of the line implies the strength of the connection. Many other connections are not shown, including reverse connections (e.g., from DR/VTA to LHb). DR, Dorsal raphe; MR, medial raphe; S, septum; DBB, nucleus of diagonal band of Broca; BST, bed nucleus of stria terminalis; LPO, lateral preoptic area; LH, lateral hypothalamus; GPi, globus pallidus internal segment; CPu, caudate and putamen; sm, stria medullaris; fr, fasciculus retroflexus. This figure was modified with permission from Hikosaka (2007a), his Figure 2.