Anatomy & Organs

Nucleus accumbens – structure, function & diseases

Nucleus accumbens

The nucleus accumbens is a relatively small part of the brain . It provides a connection between the putamen and the caudate nucleus . Its main task is to regulate the reward system.

What is nucleus accumbens?

The nucleus accumbens is assigned to the mesolimbic system . The mesolimbic system is the reward system for positive stimuli. In it, positive emotions are localized and identified by external stimuli.

Corresponding reactions to the stimuli are planned and carried out in this brain region. The triggering stimuli can be based on events that have been experienced, but can also be triggered by the ingestion of substances. For this reason, the nucleus accumbus is considered to be the region that plays an essential role in the development of addiction.

The nucleus accumbens is part of the putamen. The putamen provides an important function in controlling voluntary motor function. Together with the caudate nucleus, the plutamen forms the striatum. The striatum is part of the basal ganglia. These take over part of the motor, cognitive and limbic functions. The nucleus accumbens is a section of this region that causes motivational intention to be translated into action. The perceived emotion is converted into a so-called locomotion by the influence of the nucleus accumbens. The nucleus accumbens is the instance that represents the transition from the motivational system to the activation system.

Anatomy & Structure

The nucleus accumbens is considered the inner core of the telencephalon . This is the cerebrum . The nucleus accumbens is part of the corpus striatum . It is a nucleus in the basal ganglia that contains a group of cerebral and diencephalic nuclei.The nucleus accumbens forms a small region in the ventrorostral part of the striatum. The striatum is a switching point in the extrapyramidal motor system. The nucleus accumbens is the area where the caudate nucleus and plutamen fuse together. Its fibrous connections are similar to those of the rest of the striatum.

In the area of ​​the limbic system, it is characterized by a particularly afferent fiber structure. For this reason, this part of the basal ganglia is a special relay point for the implementation of motivation and emotion. The nucleus accumbens is thus a link between the basal ganglia and the limbic or psychomotor system. Type D2 dopamine receptors are located in the nucleus accumbens . These receptors receive signals from the neurotransmitter dopamine. This has an exciting effect.

Function & Tasks

The nucleus accumbens plays an important role in social behavior. Functionally, the nucleus accumbens represents a relay point between the emotional and locomotor systems. This means that the perceived emotions give rise to actions that are regulated by the nucleus accumbens.

The dopamine receptors present in the nucleus accumbens trigger positive feelings. These include feelings of happiness, the experience of success or euphoria . Substances such as opiates or amphetamines also affect the receptors and trigger the same positive emotions. The synaptic transmission therefore works with experienced as with artificially induced emotions. The nucleus accumbens represents the reward center. It thus plays an important role in classical conditioning. This includes learning simple stimulus-response patterns. For example, conditioning causes salivation at the sight of food.

The nucleus accumbens is the region of the brain where addiction develops. This can be an addiction to substances such as cocaine , amphetamines or opiates. But addiction to milder substances such as tobacco or nasal spray also originates in the nucleus accumbens.

From the nucleus accumbens, efferents enter the limbic system and the hypothalamus . The incoming information is processed cognitively and psychologically in this brain region. The processing process causes the vegetative response of the feeling of happiness.

Diseases

Lesions and damage to the nucleus accumbens have a direct impact on the perception of positive emotions as a result of reward. Impairments can result from cerebral hemorrhage , inflammation or after accidents. Damage to the nucleus accumbens is also possible after surgical interventions or in the case of tumor diseases .In the case of lesions of the nucleus accumbens, the distribution of so-called feelings of happiness can no longer be regulated via feedback mechanisms. The D2 type dopamine receptor mediates positive and negative symptoms of schizophrenia . Thus, all diseases are influenced by schizophrenia via the nucleus accumbens.

Dysfunction of the nucleus accumbens can negatively impact the functionality of the reward system. A dysfunction in diseases such as depression can therefore have an important influence. The disease can be intensified or depressive episodes can be triggered.

Bipolar affective disorder is characterized by a disturbed experience of emotions. Sick people suffer from an interplay of positive and negative feelings. The nucleus accumbens plays a crucial role here. Its influence can weaken or intensify the experience of emotions. Impaired functioning of the nucleus accumbens can make it impossible to learn classical conditioning. This limits the ability to react to stimuli. Many anxiety disorders are stored in the brain through classical conditioning. Damage to the nucleus accumbens can cause learned anxiety to be minimized. Fear conditioning must have occurred prior to the nucleus accumbens lesion.

Addiction is essentially influenced by the activity of the nucleus accumbens. This is a chronic condition in which persistent elevations in dopamine levels cause insensitivity to the substance in question. Discontinuation of the substance leads to severe withdrawal symptoms.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.