Ventral tegmental area: anatomy, functions and disorders
The ventral tegmental area is a region of the mesencephalon , also known as the middle brain, which is very important because of its involvement in the reinforcement circuit, responsible for the sensations of pleasure and motivated behavior. In addition, it is involved in other diverse functions when sending projections to cortical and subcortical areas.
In this article we will describe the anatomical characteristics, the main functions and the disorders that associate to the ventral tegmental area . We will focus mainly on the role played by this structure in the brain reward system.
- Related article: "Parts of the human brain (and functions)"
Anatomy of the ventral tegmental area
The concept "ventral tegmental area" refers to a set of neurons that are located at the base of the mesencephalon, the intermediate region of the brainstem. In Latin the word "tegmentum" means "covering" or "covering"; therefore, the name highlights the fact that this area constitutes a layer of neurons that covers the mesencephalon.
Four nuclei of main cells have been identified in the ventral tegmental area: the paranigral nucleus, the parabrachial pigmentosa area, the retroflexa parafascicular area and the rostromedial tegmental nucleus. The dopaminergic neurons characteristic of this region of the brain are located mainly in the first two.
Together with the substantia nigra and the retrorubral field, also located in the mesencephalon, the tegmental area contains most dopaminergic neurons of the brain. Dopamine is a neurotransmitter of the class of catecholamines that is involved in the increase of heart rate and learning by operant conditioning, among other aspects.
- Maybe you're interested: "Mesencephalon: characteristics, parts and functions"
Functions of this structure
The dopaminergic neurons of the ventral tegmental area are part of the mesocortical and mesolimbic systems . While the mesocortical system connects this region with the frontal lobes, the mesolimbic sends projections to the nucleus accumbens, a fundamental structure of the cerebral reward system, just like the ventral tegmental area.
The mesocortical path plays a fundamental role in cognition ; in particular it allows the arrival in the frontal lobes of information about emotion and motivation. After receiving these inputs, the superior brain structures generate the responses that will be executed as a consequence.
However, the main functions of the ventral tegmental area are associated with its involvement in the cerebral reward system, also known as reinforcement circuit, which starts with the dopaminergic projections of the neurons of this region. This path is intimately related to the mesolimbic system.
The brain reward system
The ventral tegmental area is a key structure of the cerebral reward system, the biological basis of pleasure and behavioral motivation, since the appetitive stimuli activate this region . In this way, the reward circuit is involved in multiple behaviors, such as those related to food, sex or addictions.
When the organism detects pleasurable stimulation, the ventral tegmental area sends dopaminergic projections to the nucleus accumbens. The increase in the concentration of the neurotransmitter in this area has a reinforcing effect on the behavior associated with obtaining pleasure or satisfaction.
When these inputs reach the cerebral cortex, the information obtained through the reinforcement circuit can be integrated and managed by the higher cognitive functions. It is important highlight the reciprocity of connections in the ventral tegmental area , which allows continuous feedback between this structure and those to which it sends eferences.
Associated disorders
Scientific research has identified several disorders that occur with alterations in the dopaminergic pathways of which the ventral tegmental area is part. In general, these types of disorders involve both mesolimbic and mesocortical pathways, which are closely linked.
The neuropsychological disorders most frequently attributed to structural and / or functional problems in the transmission of dopamine they are Parkinson's disease, attention deficit hyperactivity disorder and schizophrenia.
In the latter case, positive symptoms, such as hallucinations and delusions, are associated with alterations in the mesolimbic pathway. Failures in the mesocortical system produce negative symptoms, consisting of cognitive, emotional and motivational deficits.
On the other hand, the ventral tegmental area and the nucleus accumbens are the two regions of the nervous system in which the drugs and other potentially addictive substances they have a more significant effect.
Alcohol, nicotine, cocaine, amphetamine and heroin, among others, have agonist effects on dopamine; this explains the physiological, motor and psychological consequences of the use of these substances, both in the short and long term, including addiction.
Bibliographic references:
- Halliday, G .; Reyes, S. & Double, K. (2012). Substantia nigra, ventral tegmental area, and retrorubral fields. In Mai, J. K. & Paxinos, G. (Eds.), "The human nervous system", 439-55. New York: Academic Press.
- Holstege, G .; Georgiadis, J. R .; Paans, A. M .; Meiners, L. C .; Van Der Graaf, F. H. & Reinders, A.A. (2003). Brain activation during human male ejaculation. The Journal of Neuroscience: The official journal of the Society for Neuroscience, 23 (27): 9185-93.
- Ranaldi, R. (2014). Dopamine and reward seeking: the role of ventral tegmental area. Reviews in the Neurosciences, 25 (5): 621-30.
