Accumbens nucleus: anatomy and functions
By all it is already known that the different regions of the brain, although its operation requires its coordinated action with the rest of the brain, tend to specialize in some functions.
This article aims to show the importance of the functioning of the nucleus accumbens , a part of the brain not well known by the majority of the population, but of great relevance for the human being due to its participation 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 the septum. This nucleus is part of the ventral area of the striated body , 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 when it comes to integrating cognitive, motivational and motor aspects, and being one of the main nuclei that allows the will to be translated into action, allowing the performance of behaviors of pleasure search.
Parts of this structure
The nucleus accumbens has traditionally been divided into two sections, the central zone and the cortex, due to its different connections with other brain areas and its greater connection to the emotional or the motor.
1. Crust (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 and glutamate from various brain areas.
It is therefore the part most linked to the emotions of this structure. It also has many connections coming from the front, sending the nucleus accumbens the information collected to the thalamus and receiving back to the central zone of the nucleus accumbens.
2. Central zone (Core)
The central zone of the nucleus accumbens has functions mainly linked to the motor, being connected to the basal ganglia, the substantia nigra and the motor cortex. ANDThis area is activated to a great extent at the moment of performing actions with emotional meaning directed to a specific goal.
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 in which processes 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 special participation are the following .
1. Emotion-motivation-action integration
One of the main functions of the nucleus accumbens is to transmit the information about the subject's motivation and translate it into a motor action in order to comply with the organism's objectives. This integration comes from its connections with both the prefrontal and the basal ganglia. Thus, it allows us to do instrumental behaviors, directed to a specific purpose.
In a certain sense, this function of the cerebral amygdala has to do with a very important type of memory: emotional memory. This capacity is on the border between mental processes linked to emotion and higher psychological processes, 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 one with the frontal lobe have allowed to see how this structure has a stake in the ideation and planning of behavior , being as we have said an important point of integration between the motivational aspects of the behavior and its implementation.
3. Evaluation of the situation
The participation of this structure is also given an evaluative level, integrate emotional information with adaptive assessment that makes the front. In this way it is possible to associate a stimulus to a subjective evaluation 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 process , since it is linked to reward experimentation. This brain nucleus is part of the mesolimbic pathway, forming part of the brain reward center. Specifically, it is in this area where stimulant drugs act, producing an increase in brain dopamine levels.
5. Obtaining pleasure
Although it is not the only brain structure linked to the experimentation of pleasure, the nucleus accumbens maintains a close link with its achievement.And is that different experiments have shown that although its inhibition does not eliminate the desire to obtain a reinforcer, it does produce a decrease or suppression of the necessary behaviors to obtain the object of desire. 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 above mentioned points show that the nucleus accumbens It has a great relevance when it comes to establishing automation and learning of behaviors aimed at obtaining a reward. It also participates in the habituation process.
7. Aggressiveness and risky behavior
An overactivity in the nucleus accumbens can lead to aggressive behavior . Faced with a very high presence of dopamine and other alterations that hinder behavioral inhibition, it can lead to personal satisfaction without assessing the risks.
In fact, the 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 them to seek their own reward with indifference to the consequences for the others.
- Fernández-Espejo, E. (2000). How does 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.