The nucleus accumbens is in the basal forebrain at the bottom of the striatum, one in each hemisphere. It lies below the internal capsule and has no sharp border: it merges into the caudate nucleus medially and upwards and into the putamen laterally. [1][2]
Not a separate shape in this atlas; lit: the part that holds it. Lit: the whole caudate nucleus and putamen, on both sides. The nucleus accumbens is the lowest part of the striatum, under these two; it has no sharp border and merges into the caudate nucleus toward the midline and into the putamen to the side. It has no shape of its own in the BodyParts3D model, so nothing is drawn at a guessed point. [1][3]
The 3D brain needs JavaScript. The text below still says where the nucleus accumbens is and what it does.
Slice
The caudate nucleus and putamen are lit together; the nucleus accumbens is not drawn on its own. The front (coronal) slice button cuts through them. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Lit here: the caudate nucleus and the putamen, the parts that hold the nucleus accumbens — see each on its own page.
Where it is
It is a region of the basal forebrain, in front of (rostral to) the preoptic area of the hypothalamus; each cerebral hemisphere has its own. [2]
It occupies the lowest part of the striatum, below the internal capsule, and extends back beneath the capsule’s anterior limb as far as the end of the anterior commissure. [1]
It has no clear boundaries: it passes into the putamen laterally and into the caudate nucleus medially and upwards; fibres of the internal capsule surround it from above. [1]
With the olfactory tubercle it forms the ventral striatum; the dorsal striatum is the caudate nucleus and putamen, and together they make the striatum, the main component of the basal ganglia. [2][3]
It has an inner core and an outer shell; the shell, unlike the core, is considered part of the extended amygdala. [2]
What it does
As a whole it has a significant role in the cognitive processing of motivation, aversion, reward (incentive salience, pleasure and positive reinforcement) and reinforcement learning. [2]
The ventral striatum, and the nucleus accumbens in particular, mainly mediates reward, cognition, reinforcement and motivational salience; the dorsal striatum handles motor-related cognition, some executive functions and stimulus-response learning. [3]
Part of its core is centrally involved in bringing on slow-wave sleep, and the core encodes new motor programs that help win a reward in the future. [2]
A small “hedonic hotspot” in the medial shell is responsible for the “liking” of some intrinsic rewards. [2]
It plays a lesser role in processing fear, impulsivity and the placebo effect. [2]
Connections
Glutamate inputs come from the prefrontal cortex, the basolateral amygdala, the ventral hippocampus, the midline and intralaminar thalamic nuclei and the ventral tegmental area (VTA). [2]
Dopamine arrives from the ventral tegmental area through the mesolimbic pathway. [2][3]
Its output neurons project to the ventral pallidum, which projects to the medial dorsal nucleus of the thalamus and from there to the prefrontal cortex; other outputs reach the VTA, the substantia nigra and the reticular formation of the pons. [2]
Inside it
Mostly medium spiny neurons using GABA, carrying mainly D1-type or D2-type dopamine receptors; neurons in the core have more dendritic spines and branches than those in the shell. [2]
Other names
Abbreviated NAc or NAcc; also the accumbens nucleus, and formerly the nucleus accumbens septi, Latin for “nucleus adjacent to the septum”. [2]
Size
The model has no shape for the nucleus accumbens itself, so it is not measured here. The left caudate nucleus that holds it measures about 64 mm front to back, 37 mm top to bottom and 32 mm side to side on this model (the box it fits in, not its volume). [4]
The model has no shape for the nucleus accumbens itself, so it is not measured here. The left putamen that holds it measures about 43 mm front to back, 26 mm top to bottom and 18 mm side to side on this model (the box it fits in, not its volume). [4]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.