Nucleus accumbens

	Email		Print
	Bookmark		Link

Nucleus accumbens

The nucleus accumbens (NAcc), also known as the accumbens nucleus or as the nucleus accumbens septi (Latin for nucleus
Nucleus (neuroanatomy)

In neuroanatomy, a nucleus is a brain structure consisting of a relatively compact cluster of neurons. It is one of the two most common forms of nerve cell organization, the other being layered structures such as the cerebral cortex or cerebellum....
leaning against the septum
Septum

A septum is a partition separating two cavities or spaces. Examples include:*Nasal septum: the cartilage wall separating the nostrils of the human nose....
), is a collection of neuron

Neuron

Neurons are responsive cell in the nervous system that process and transmit information by electrochemical Signal . They are the core components of the brain, the vertebrate spinal cord, the invertebrate ventral nerve cord, and the peripheral nerves....
s within the forebrain. It is thought to play an important role in reward

Reward

A reward may refer to:*Bounty , a reward, often money, offered as an incentive*Reward website, a website that offers rewards for performing tasks...
, laughter

Laughter

Laughter is an audible expression , or appearance of merriment or happiness, or an inward feeling of joy and pleasure . It may ensue from jokes, tickling, and other stimuli....
, pleasure

Pleasure

Pleasure is commonly conceptualized as a positive experience, happiness, entertainment, enjoyment, ecstasy , and Euphoria . However, it is a difficult concept to define as the experience of pleasure differs from individual to individual....
, addiction

Addiction

The term "addiction" is used in many contexts to describe an obsession, compulsion, or excessive physical dependence or psychological dependence, such as: drug addiction, video game addiction, crime, alcoholism, compulsive overeating, problem gambling, computer addiction, pornography addiction, etc....
, fear

Fear

Fear is an emotional response to threats and danger. It is a basic survival mechanism occurring in response to a specific stimulus, such as pain or the threat of pain....
, and the placebo effect

Placebo effect

Placebo effect may refer to:* Placebo, the tendency of any medication or treatment, even an inert or ineffective one, to exhibit results simply because the recipient believes that it will work...
.

Each half of the brain has one nucleus accumbens. It is located where the head of the caudate

Caudate nucleus

The caudate nucleus is a nucleus located within the basal ganglia of the brains of many animal species. The caudate, originally thought to primarily be involved with control of voluntary movement, is now known to be an important part of the brain's learning and memory system....
and the anterior portion of the putamen

Putamen

The putamen is a round structure located at the base of the forebrain . The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that comprises the basal ganglia....
meet just lateral to the septum pellucidum

Septum pellucidum

The septum pellucidum is a thin, triangular, vertical membrane separating the lateral ventricles of the brain. It separates the anterior horn of the left and right lateral ventricles....
. The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum, which is part of the basal ganglia

Basal ganglia

The basal ganglia are a group of Nucleus in the brain interconnected with the cerebral cortex, thalamus and brainstem. Mammalian basal ganglia are associated with a variety of functions: motor control, cognition, emotions, and learning....
.

The nucleus accumbens can be divided into two structures -- the nucleus accumbens core and the nucleus accumbens shell.

Discussion

Ask a question about 'Nucleus accumbens'

Start a new discussion about 'Nucleus accumbens'

Answer questions from other users

Full Discussion Forum

Encyclopedia

Neuron

Reward

A reward may refer to:*Bounty , a reward, often money, offered as an incentive*Reward website, a website that offers rewards for performing tasks...
, laughter

Laughter

Laughter is an audible expression , or appearance of merriment or happiness, or an inward feeling of joy and pleasure . It may ensue from jokes, tickling, and other stimuli....
, pleasure

Pleasure

Addiction

Fear

Fear is an emotional response to threats and danger. It is a basic survival mechanism occurring in response to a specific stimulus, such as pain or the threat of pain....
, and the placebo effect

Placebo effect

Caudate nucleus

Putamen

Septum pellucidum

Basal ganglia

Cell types

The principal neuronal cell type found in the nucleus accumbens is the medium spiny neuron

Medium spiny neuron

The medium spiny neurons are a special type of inhibitory cells representing approximately 90% of the neurons within the corpus striatum of the basal ganglia....
. The neurotransmitter

Neurotransmitter

Neurotransmitters are chemistry which relay, amplify and modulate signals between a neuron and another cell . Neurotransmitters are packaged into vesicles that cluster beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to receptors in the membrane on the postsynaptic side of...
produced by these neurons is gamma-aminobutyric acid

Gamma-aminobutyric acid

γ-Aminobutyric acid is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays an important role in regulating neuronal excitability throughout the nervous system....
(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.

While 95% of the neurons in the nucleus accumbens are medium spiny GABA-ergic projection neurons, other neuronal types are also found such as large aspiny cholinergic

Cholinergic

A receptor is cholinergic if it uses acetylcholine as its neurotransmitter.Cholinergic means related to the neurotransmitter acetylcholine, and is typically used in a neurological perspective....
interneuron

Interneuron

An interneuron is a multipolar neuron which connects afferent neurons and efferent neurons in neural pathways. Like motor neurons, interneuron cell body are always located in the central nervous system ....
s.

Output and input

The output neurons of the nucleus accumbens send axon projections to the ventral analog of the globus pallidus

Globus pallidus

The globus pallidus is a sub-Cerebral cortex structure of the brain. It is a major element of the basal ganglia system. In this system, it is a major constituent of the basal ganglia core, which consists of the striatum and its direct targets: globus pallidus and substantia nigra....
, known as the ventral pallidum (VP). The VP, in turn, projects to the mediodorsal (MD) nucleus of the dorsal thalamus

Thalamus

The thalamus is a pair and symmetric part of the brain. It constitutes the main part of the diencephalon....
, which projects to the prefrontal cortex

Prefrontal cortex

The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the primary motor cortex and premotor cortex areas....
. Other efferents from the nucleus accumbens include connections with the substantia nigra

Substantia nigra

The substantia nigra is a brain structure located in the mesencephalon that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", as parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in dopaminergic neurons....
and pontine reticular formation. Major inputs to the nucleus accumbens include prefrontal association cortices, basolateral amygdala

Amygdala

The are almond-shaped groups of neurons located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotions, the amygdalae are considered part of the limbic system....
, and dopaminergic neurons located in the ventral tegmental area (VTA), which connect via the mesolimbic pathway

Mesolimbic pathway

The mesolimbic pathway is one of the dopaminergic pathways in the brain. The pathway begins in the ventral tegmentum of the mesencephalon and connects to the limbic system via the nucleus accumbens, the amygdala, and the hippocampus as well as to the prefrontal cortex....
. 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

Recreational drug use

Recreational drug use is the use of psychoactive drugs for recreational purposes rather than for employment, Medicine or Spirituality purposes, although the distinction is not always clear ....
such as cocaine

Cocaine

Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine....
and amphetamine

Amphetamine

Amphetamine and related drugs such as methamphetamine are a group of drugs that act by increasing levels of norepinephrine, serotonin, and dopamine in the brain....
, which cause a manifold increase in dopamine

Dopamine

Dopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the human brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors ? D1, D2, D3, D4 and D5, and their variants....
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.

Research

In the 1950s, Olds and Milner implanted electrodes into the septal area of the rat and found that the rat chose to press a lever which stimulated it. It continued to prefer this even over stopping to eat or drink. This suggests that the area is the 'pleasure center' of the brain.

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. A recent study found that it is involved in the regulation of emotions induced by music

Music

Music is an art form whose media is sound organized in time. Common elements of music are pitch , rhythm , dynamics , and the sonic qualities of timbre and texture ....
, perhaps consequent to its role in mediating dopamine release. The Nucleus Accumbens plays a role in rhythmic timing and is considered to be of central importance to the limbic-motor interface (Mogensen).

In April 2007, two research teams reported on having inserted electrodes into the nucleus accumbens in order to use deep brain stimulation

Deep brain stimulation

In neurotechnology, deep brain stimulation is a surgery treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain....
to treat severe depression

Clinical depression

Major depressive disorder is a mental disorder characterized by a pervasive depression , low self-esteem, and anhedonia in normally enjoyable activities....
.

Additionally, in July 2007, researcher Jon-Kar Zubieta published findings that the nucleus accumbus is central to the machinery of the placebo effect

Placebo effect

Placebo effect may refer to:* Placebo, the tendency of any medication or treatment, even an inert or ineffective one, to exhibit results simply because the recipient believes that it will work...
. He and his colleagues found that people who showed greater activation of the NAcc during a reward-expectation task also showed a greater anticipation of effectiveness of a placebo

Placebo

The placebo effect is a phenomenon in medicine where the results of a medical treatment are affected by their symbolism, and not just their medical value....
.

Additional images

External links

Part of "The Brain From Top to Bottom." at thebrain.mcgill.ca