Nucleus accumbens: anatomy and functions

It is well known that different regions of the brain, although their functioning requires coordinated action with the rest of the brain, tend to specialize in certain functions.

This article aims to show the importance of the functioning of the nucleus accumbens, A part of the brain not too well known to the majority of the population, but of great importance to humans because of its involvement in the brain 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 with the septum. This nucleus is part of the ventral area of ​​the corpus striatum, Being one of the nuclei that make up the basal ganglia.

The nucleus accumbens is also part of the brain reward circuit, having a great influence in the integration of cognitive, motivational and motor aspects, and being one of the main nuclei which allows to translate will into action, allowing to perform pleasure-seeking behaviors.

Parts of this structure

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

1. Shell

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

It is therefore the part most linked to the emotions of this structure. It also has many connections coming from the front, send the nucleus accumbens the information gathered in 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 primarily related to motor skills, being connected to the basal ganglia, substantia nigra and motor cortex. Ithis area is largely activated when performing actions of emotional significance aimed at a specific objective.

main duties

The location of this structure and the connections it maintains with different areas of the brain make 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 more directly the processes in which it participates.

While 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 as follows.

1. Emotion-motivation-action integration

One of the main functions of the nucleus accumbens is to convey information about the subject’s motivation and translate it into motor action in order to fulfill the objectives of the organism. This integration comes from its connections to the prefrontal and basal nuclei. Thus, it allows us to make instrumental behaviors, aimed at a specific goal.

In a way, this function of the cerebral amygdala has to do with a very important type of memory: emotional memory. This ability is at the border between emotional processes linked to emotion and higher psychological processes, because on the one hand it works with emotions and on the other hand it influences decision-making and the creation of concepts.

2. Influence behavior planning

The connections of the nucleus accumbens with that with the frontal lobe made it possible to see how this structure participates in ideation and behavior planning, Being as we 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 assigned an evaluative level, in the integrate emotional information with adaptive assessment who performs the frontal. In this way, it is possible to associate a stimulus with a subjective evaluation through a process which also concerns emotional memory.

4. Role in drug addiction

The nucleus accumbens plays an important role in the addiction process, As it is related to reward experimentation. This brain nucleus is part of the mesolimbic pathway, forming part of the brain’s reward center. Specifically, this is where stimulant drugs work, producing increased levels of dopamine in the brain.

5. Get pleasure

While this is not the only brain structure linked to the experience of pleasure, the nucleus acumbens if it maintains a close link with its realization. And it is that different experiments have shown that if its inhibition does not eliminate the desire to obtain an enhancer, it produces a decrease or a suppression of the behaviors necessary to obtain the object of the desire. The observed data show that participation of the nucleus accumbens occurs in addiction processes, as well as in food and sex.

6. Learning and memory

The above points show that the nucleus accumbens has great relevance in establishing automation and learning conduct aimed at obtaining a reward. It also participates in the habituation process.

7. Aggression and risky behavior

Overactivity in the nucleus accumbens can lead to aggressive behavior. Faced with a very strong presence of dopamine and other alterations making behavioral inhibition difficult, it can lead to the search for personal satisfaction without evaluating the risks.

Indeed, studies in people with psychopathy seem to indicate that these people present, among other disorders, a severe imbalance at the level of the nucleus accumbens, suffering from an hyperreactivity to dopamine which can lead to seek their own reward whatever in be the consequences for others.

Bibliographical references:

  • Fernández-Mirall, I. (2000). How does the nucleus accumbens work? Tower. Neurol. 30: 845-9.

  • Kandel, ER (2001). Principles of neuroscience. 1st edition. McGraw-Hill.

  • Salamone, JD; Correa, M .; Mingote, S. and Weber, SM (2003). Dopamine Nucleus Accumbens and the regulation of exertion in foraging behavior: implications for studies in natural motivation, psychiatry, and addiction. Journal of Pharmacology and Experimental Therapeutics, 305 (1). 1-8.

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