Term: Nucleus accumbens

Definition: There is no morphologically distinct boundary between this ventromedial region of the striatum and the caudoputamen; Gurdjian (1928) first defined the nucleus accumbens in the rat as that part of the ventromedial striatum lacking massive bundles of ascending and descending fibers, which is still a useful working criterion. It is common to divide the nucleus accumbens roughly into core (adjacent to the caudoputamen) and shell (external) regions, although there is controversy about where to draw a boundary between the two (see Groenewegen et al. 1999).

Nomenclature: Swanson-2004