Term: Substantia innominata

Definition: Jones et al. 1976. This region was renamed the ventral pallidum (Heimer and Wilson 1975), and then later divided by Heimer and colleagues into a rostral part now referred to as the ventral pallidum and a caudal part referred to as part of the extended amygdala (see de Olmos and Heimer 1999, and a critique by Swanson 2003b). The substantia innominata contains characteristic subpopulations of scattered, cortically projecting cholinergic and noncholinergic neurons (Rye et al. 1984) that in some animals (especially primates), but not in rats, form distinct cell clusters known as the basal nuclei of Meynert (see Gorry 1963). These cholinergic cells extend into the medial septal complex, the magnocellular nucleus, and perhaps to a very limited extent the lateral preoptic area. The term magnocellular basal "nucleus" has been introduced to refer to the basal forebrain cholinergic neurons that project to the cerebral cortex (Saper 1984). A developmental model for how the substantia innominata comes to lie between two parts of the striatum (nucleus accumbens-striatal fundus and the olfactory tubercle) has been presented elsewhere (Alvarez-Bolado et al. 1995).

Nomenclature: Swanson-2004