Nucleus accumbens: anatomy and functions

By all it is already known that the different regions of the brain, although for their functioning they are precise of their coordinated action with the rest of the brain, they tend to specialize in some functions.

This article aims to show the importance of the nucleus accumbens., a part of the brain not well known by the majority of the population, but of great relevance to humans due to its involvement in the brain's reward system and the integration of motivation and action.

Where is the nucleus accumbens?

The nucleus accumbens is a subcortical brain structure, located at the point where the caudate nucleus and putamen meet the septum. This nucleus is part of the ventral area of ​​the striatum, being one of the nuclei that make up the basal ganglia.

The nucleus accumbens is also part of the brain's reward circuit, having a great influence when it comes to integrating cognitive and motivational aspects and motors, and being one of the main nuclei that allows the will to be translated into action, allowing the performance of pleasure-seeking behaviors.

Parts of this structure

The nucleus accumbens has traditionally been divided into two sections, central zone and cortex, due to its different connections with other brain areas and its greater link to the emotional or to the motor.

1. Bark (Shell)

This part of the nucleus accumbens is characterized by its high number of connections with the limbic system and the hippocampus, receiving both dopamine and serotonin Y glutamate of various brain areas.

It is therefore the most linked to emotions of this structure. It also has many connections coming from the front, sending the nucleus accumbens the collected information to the thalamus and receiving back to the central area of ​​the nucleus accumbens.

2. Central zone (Core)

The central area of ​​the nucleus accumbens has functions mainly related to motor skills, being connected to the basal ganglia, the substantia nigra and the motor cortex. ANDThis area is largely activated when performing actions with emotional significance directed to a specific goal.

Principal functions

The location of this structure and the connections it maintains with different brain areas makes the nucleus accumbens a very important structure. However, to be able to see the importance of this structure and its implications, it is necessary to visualize in a more direct way which processes it participates in.

Although many of them are shared by the rest of the basal ganglia, Some of these processes in which the nucleus accumbens has a special participation are the following.

1. Emotion-motivation-action integration

One of the main functions of the nucleus accumbens is to transmit information about the subject's motivation and translate it into a motor action in order to meet the objectives of the body. This integration comes from their connections with both the prefrontal as with the basal ganglia. Thus, it allows us to do instrumental behaviors, directed to a specific purpose.

In a sense, this function of the brain amygdala has to do with a very important type of memory: the emotional memory. This capacity is on the border between mental processes linked to emotion and psychological processes superiors, since on the one hand it works with emotions and on the other it influences decision-making and the creation of concepts.

2. Influences behavior planning

The connections of the nucleus accumbens with the with the frontal lobe have allowed to see how this structure participates in the ideation and planning of behavior, being as we have said an important point of integration between the motivational aspects of behavior and its implementation.

3. Assessment of the situation

The participation of this structure is also given an evaluative level, by integrate emotional information with adaptive assessment performed by the front. In this way, it is possible to associate a stimulus with a subjective assessment through a process that also has to do with emotional memory.

4. Role in addiction

The nucleus accumbens plays an important role in the addictive processas it is linked to rewarding experimentation. This brain nucleus is part of the mesolimbic pathway, forming part of the brain's reward center. Specifically, it is in this area where stimulant drugs act, producing an increase in the levels of dopamine cerebral.

5. Getting pleasure

Although it is not the only brain structure linked to the experience of pleasure, the nucleus accumbens is closely linked to its achievement. And it is that different experiments have shown that although its inhibition does not eliminate the desire to obtain a reinforcer, does produce a decrease or suppression of the behaviors necessary to obtain the object of wish. The observed data show that the participation of the nucleus accumbens occurs in addictive processes, as well as in food and sex.

6. Learning and memory

The aforementioned points show that the nucleus accumbens has great relevance when establishing automation and learning of behaviors aimed at obtaining a reward. He also participates in the habituation process.

7. Aggression and risky behaviors

An overactivity in the nucleus accumbens can lead to aggressive behaviors. Faced with a very high presence of dopamine and other alterations that hinder behavioral inhibition, it can lead to seeking personal satisfaction without assessing the risks.

In fact, studies conducted in people who have psychopathy seem to indicate that these people have, among other alterations, a severe imbalance in the nucleus accumbens, suffering from a hyperreactivity to dopamine that could induce to seek one's own reward with indifference to the consequences for the others.

Bibliographic references:

• Fernández-Espejo, E. (2000). How does the nucleus accumbens work? Rev. Neurol. 30: 845-9.

• Kandel, E. R. (2001). Principles of Neuroscience. 1st edition. McGraw-Hill.

• Salamone, J.D.; Correa, M.; Mingote, S. & Weber, S.M. (2003). Nucleus Accumbens Dopamine and the Regulation of Effort in Food-Seeking Behavior: Implications for Studies of Natural Motivation, Psychiatry and Drug Abuse. Journal of Pharmacology and Experimental Therapeutics, 305 (1). 1-8.