Nucleus Accumbens

dopamine

Striatum

The nucleus [noo-klee-uhsaccumbens [uh-cum-benz] is a collection of neurons within the striatum, a component of the forebrain (prosencephalon). It is thought to play an important role in reward, pleasure, laughter, addiction, aggression, fear, and the placebo effect.

Each half of the brain has one nucleus accumbens, which, along with the olfactory tubercle collectively form the ventral striatum, which is part of the basal ganglia, part of the cerebrum vital to movement. The nucleus accumbens plays a role in rhythmic timing and is considered to be of central importance to the limbic-motor interface.

The principal neuronal cell type found in the nucleus accumbens is the medium spiny neuron. The neurotransmitter produced by these neurons is gamma-aminobutyric acid (GABA), one of the main inhibitory neurotransmitters of the central nervous system. These neurons are also the main projection or output neurons of the nucleus accumbens. Major inputs to the nucleus accumbens include prefrontal association cortices, basolateral amygdala, and dopaminergic neurons located in the ventral tegmental area (VTA), which connect via the mesolimbic pathway. Thus the nucleus accumbens is often described as one part of a cortico-striato-thalamo-cortical loop.

Dopaminergic input from the VTA is thought to modulate the activity of neurons within the nucleus accumbens. These terminals are also the site of action of highly-addictive drugs such as cocaine and amphetamine, which cause a manifold increase in dopamine levels in the nucleus accumbens. In addition to cocaine and amphetamine, almost every recreational drug has been shown to increase dopamine levels in the nucleus accumbens.

Although the nucleus accumbens has traditionally been studied for its role in addiction, it plays an equal role in processing many rewards such as food and sex. Interestingly, the nucleus accumbens is selectively activated during the perception of pleasant, emotionally arousing pictures and during mental imagery of pleasant, emotional scenes. A recent study found that it is involved in the regulation of emotions induced by music, perhaps consequent to its role in mediating dopamine release.

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