The human nervous system is made up of millions of neurons, which connect to each other to form complex neural networks.
Different networks are usually responsible for transmitting different information, allowing the operation of different systems with different functions. One of the most important pathways for our survival is the mesolimbic pathway, Which we turn to analyze throughout this article.
The mesolimbic tract: one of the main dopaminergic pathways
Mesolimbic is understood to be one of the main dopaminergic circuits in the brain, Which connects the midbrain to the limbic system from the ventral tegmental area to the nucleus accumbens, connecting to other structures such as the amygdala and even the prefrontal cortex.
The mesolimbic pathway has been identified with the brain reward mechanism, Including most of the structures that are part of it. It is therefore a circuit of great importance for the development and functioning of human beings, being fundamental to capturing and experiencing feelings of pleasure and gratification.
This allows us to address stimulation, for example allowing us to want to eat or maintain relationships because of the experience of satisfaction. In the same way. its proper functioning of this path allows us to learn by reinforcing our behavior, seeking to repeat the same actions in these stimulus situations similar to those that caused their activation of feelings of gratification. Along with this, it allows us to a large extent to learn and condition behavior. It also has an important role in aspects such as the management of emotions and the physiological reactions that arise from them, behavioral control, impulsivity and motivation.
Main structures involved
The mesolimbic pathway is not a structure in itself, but a collection of these that work together to form a network through which information flows.
There are many cortical and subcortical structures that are part of this pathway, resulting in the following among the most notable.
1. Ventral tegmental zone
This brain region is the starting point of the mesolimbic pathway, located in the brainstem. It is one of the areas that has the most dopaminergic receptors, participating in both the mesolimbic and mesocortical pathways. The ventral tegmental zone plays an important role in maintaining motivation, emotion and cognition, as well as in pleasant experimentation. Neurons in this area modulate the release of dopamine in other areas of the mesolimbic pathway.
2. Nucleus accumbens
Part of the basal ganglia, the nucleus accumbens is one of the most important structures in the brain reward circuit and the mesolimbic pathway. And it is that this nucleus largely controls the release of dopamine in the brain. It is in this area that most drugs work, as well as one of the most linked to the processes of addiction and acquisition of addictions. It participates in the integration of emotion and motivation to transform them into actions, as well as in the management of aggression, memory and behavior planning (by its connection to the prefrontal).
The amygdala complex is an important part of the mesolimbic tract, linking emotion to physiological responses. and behavioral specific to their experimentation. This is the main core that deals with emotional management, especially in the case of fear (which partly explains the feelings of fear generated by hallucinations in schizophrenic subjects) and aggression. It also influences sexuality and the feeling of satiety.
The hippocampus is one of the regions of the limbic system most associated with memory and learning, allowing the formation and retrieval of memories and associating them with the emotional evaluation that is made of the experience.
5. Core of terminal striae
As part of the limbic system, this nucleus brings together all the fibers that connect the thalamus and the amygdala. It is linked to stress management and sexuality (there are differences between genders and gender identities in this area).
6. Prefrontal cortex
The prefrontal cortex is one of the areas that govern the cognitive aspects of behavior, Allow the use of skills such as impulse planning and inhibition. The mesolimbic pathway also connects to this part of the cerebral cortex.
Role in different disorders
Mesolimbic pathway dysfunction, either due to hyperfunction or hypofunction thereof, Has been frequently linked to experiences with different mental and behavioral disorders. Specifically, some of the disorders to which this pathway has been most linked are as follows.
1. Schizophrenia and other psychotic disorders
The main disorder with which it is associated, in schizophrenia, it has been observed that the presence of hyperactivation of the mesolimbic pathway due to excess dopamine is linked to the onset of hallucinations and other positive symptoms such as restlessness, impulsivity and chaotic and disorganized behavior.
But not only in schizophrenia, but it has also been found to associate this pathway with symptoms of other psychotic disorders such as chronic delusional disorder, schizophreniform disorder, or acute psychotic disorder, among others. The mesolimbic pathway is actually the primary focus of most neuroleptics, and working with it is essential to solving problems of a psychotic nature.
2. Drug addiction and abstinence
As noted above, the mesolimbic pathway is also part of the brain reward circuit, so it is associated with feelings of pleasure. In this sense, it emphasizes its importance in explaining the addictive process of drug addicts, which is due to the facilitation and agonism of dopamine which tend to generate a large number of substances.
In abstinence, the level of dopamine produced naturally by the brain, as opposed to that in schizophrenia, It is insufficient to maintain normative functioning, so that symptoms such as discomfort appear and the urge or desire for consumption is generated.
3. Eating disorders
As a fundamental part of the brain reward circuit, the mesolimbic pathway is also involved in the feeding process. and is related to the sensations of pleasure we experience when we eat. Activation of this pathway is closely related to the presence of eating disorders leading to loss of impulse control, as with binge eating in binge eating and binge eating.
Although obesity per se is not a mental disorder, excessive food consumption despite being full or in response to perceived anxiety and stress is also largely due to the pleasure gained through the activation of this way.
4. Other disorders
Mesolimbic pathway dysfunction has also been linked to the presence of problems related to aggression and pulse control. In general, it is also linked to compulsive behavior, and this pathway can be affected by other disorders such as OCD or paraphilias.
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