Ventral tegmental zone: anatomy, functions and disorders

The ventral tegmental area is a region of the midbrain, Also known as the midbrain, which is very important for its involvement in the reinforcement circuit, responsible for feelings of pleasure and motivated behaviors. It is also involved in various other functions by sending projections to the cortical and subcortical areas.

In this article we will describe the anatomical features, the main functions and disorders associated with the ventral tegmental area. We will mainly focus on the role that this structure plays in the brain’s reward system.

    Anatomy of the ventral tegmental zone

    The concept of “ventral tegmental zone” refers to a set of neurons located at the base of the midbrain, the intermediate region of the brainstem. In Latin, the word “tegmentum” means “coating” or “coating”; therefore, the name emphasizes the fact that this area constitutes a layer of neurons that covers the midbrain.

    Four main cell nuclei have been identified in the ventral tegmental area: the paranigral nucleus, the pigmented parabrachial area, the retroflex parafascicular area and the rostromedial tegmental nucleus. The dopaminergic neurons characteristic of this region of the brain are located mainly in the first two.

    Along with the substantia nigra and the retroubral field, also located in the midbrain, the tegmental zone contains most dopaminergic neurons of the brain. Dopamine is a catecholamine class neurotransmitter which participates, among other things, in increasing heart rate and in training by conditioning.

      Functions of this structure

      Dopaminergic neurons in the ventral tegmental area they are part of the mesocortical and mesolimbic systems. While the mesocortical system connects this region to the frontal lobes, the mesolimbic sends projections to the nucleus accumbens, a fundamental structure of the brain reward system, just like the ventral tegmental area.

      The mesocortical pathway plays a key role in cognition; in particular, it allows information on emotion and motivation to arrive in the frontal lobes. After receiving these inputs, the higher brain structures generate the responses which will be executed accordingly.

      However, the main functions of the ventral tegmental zone are associated with their involvement in the brain reward system, also known as the reinforcement circuit, which begins with dopaminergic projections from neurons in this region. This path is closely related to the mesolimbic system.

      The brain’s reward system

      The ventral tegmental area is a key structure of the brain reward system, the biological basis of pleasure and behavioral motivation, as appetitive stimuli activate this region. Thus, the reward circuit is involved in multiple behaviors, such as those related to food, sex or addictions.

      When the body detects a pleasant stimulation, the ventral tegmental area sends dopamine projections to the nucleus accumbens. Increasing 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 higher cognitive functions. It is important highlight the reciprocity of the connections of the ventral tegmental zone, This allows continuous feedback between this structure and those to which it sends references.

      associated disorders

      Scientific research has identified several disorders that occur with alterations in the dopaminergic pathways of which the ventral tegmental area is a part. Usually, these types of disorders involve both the mesolimbic and mesocortical pathways, which are closely related.

      The most common neuropsychological disorders attributed to structural and / or functional problems in the transmission of dopamine 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 of the mesocortical system produce negative symptoms, consisting of cognitive, emotional and motivational deficits.

      On the other hand, the ventral tegmental zone 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 dopamine agonist effects; this explains the physiological, motor and psychological consequences of the use of these substances, in the short and long term, including drug addiction.

      Bibliographical references:

      • Halliday, G .; Reyes, S. and Double, K. (2012). Dark matter, ventral tegmental zone and retroubral fields. In Mai, JK and Paxinos, G. (Eds.), “The Human Nervous System”, 439-55. New York: Academic Press.
      • Holstege, G .; Georgiadis, JR; Paans, AM; Meiners, LC; Van Der Graaf, FH and Reinders, AA (2003). Activation of the brain 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 the search for rewards: the role of the ventral tegmental zone. Opinion in Neurosciences, 25 (5): 621-30.

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