Anatomical mapping of brain stimulation reward sites in the anterior hypothalamic area: special attention to the stria medullaris.

The boundaries and relative fiber density of the brain stimulation reward systems of the anterior hypothalamic area were mapped at the level of the stria medullaris using a dorsal-ventral moveable electrode. Three clusters of reward sites were observed. One cluster was just medial to the stria medullaris, a second larger cluster was within the boundaries of the myelinated fibers of the stria, and a third cluster was observed just lateral to the stria in the medial forebrain bundle. These data are consistent with the view that there exist at least two anatomically distinct brain stimulation reward pathways connecting the midbrain and forebrain: one in the medial forebrain bundle and a second in the dorsal diencephalic bundle.