NAcc shell

Nucleus accumbens
Medial surface, person facing to the left. Nucleus accumbens is very roughly in Brodmann area 34
Nucleus accumbens of the mouse brain
Details
Part of	Mesolimbic pathway Basal ganglia (Ventral striatum)
Components	Nucleus accumbens shell Nucleus accumbens core
Identifiers
Latin	nucleus accumbens septi
Acronym(s)	NAc or NAcc
MeSH	A08.186.211.730.885.105.683
NeuroNames	hier-259
NeuroLex ID	Nucleus accumbens
Dorlands /Elsevier	n_11/12580142
TA	A14.1.09.440
FMA	61889
Anatomical terms of neuroanatomy []

The nucleus accumbens (NAc or NAcc), also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus adjacent to the septum) is a region in the basal forebrain rostral to the preoptic area of the hypothalamus. The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum, which is part of the striatum the main component of the basal ganglia. The dopaminergic neurons of the mesolimbic pathway project onto the GABAergic medium spiny neurons of the nucleus accumbens and olfactory tubercle. Each cerebral hemisphere has its own nucleus accumbens, which can be divided into two structures: the nucleus accumbens core and the nucleus accumbens shell. These substructures have different morphology and functions.

Different NAcc subregions (core vs shell) and neuron subpopulations within each region (D1-type vs D2-type medium spiny neurons) are responsible for different cognitive functions. As a whole, the nucleus accumbens has a significant role in the cognitive processing of aversion, motivation, reward (i.e., incentive salience, pleasure, and positive reinforcement), and reinforcement learning; hence, it has a significant role in addiction. It plays a lesser role in processing fear (a form of aversion), impulsivity, and the placebo effect. It is involved in the encoding of new motor programs as well.