Brain Anti-reward Circuit: What It Is And How It Works
In neuroscience, the idea of the reward circuit is widely known. It is the neurological basis behind carrying out pleasurable behaviors, playing an important role in the development of addictions.
However, it seems that there is a similar mechanism that is contrary to this, a set of brain areas that are involved in producing unpleasant sensations when performing a certain behavior.
This set of areas has been called the anti-reward circuit And, although it must be said that research is still being done on which specific areas are involved and what exactly it is used for, below we are going to talk about this peculiar mechanism.
One of the most well-known concepts in neurophysiology is the idea of the reward circuit. This consists of a set of brain mechanisms that are attributed to associating certain situations with sensations of pleasure.
Thus, The brain learns to associate substances, behaviors or any other aspect with positive emotions, satisfaction and well-being It is thanks to this system that we feel motivated to carry out actions or consume substances that we know will give us pleasure, being a very important neurological component in motivation.
As a counterpart to this system, the existence of another circuit has been proposed whose function would be to serve, in one way or another, as a regulator of behavior and mood. This is the anti-reward circuit, which consists of a network of brain regions that gives rise to negative physical and emotional emotions when faced with certain events, substances and behaviors. That is, in the same way that the reward system makes us feel pleasure, the anti-reward system makes us feel unhappy or, at the very least, less satisfied.
Neurophysiological bases
The idea of the anti-reward circuit is quite recent, and this is evidenced by the fact that today little is known about how it works and what specific areas are involved in its activation. However, we do know some brain regions that are suspected to be involved, in addition to other biochemical bases that could explain their activation.
These areas would be certain regions of the amygdala and the stria terminalis, close to the thalamus Among the neurotransmitters involved we would have corticotropin, a substance that has a lot to do with the amygdala since it seems that this structure is an important point in the corticotropin release system. In addition to this neurotransmitter, others involved in the anti-reward circuit are dynorphin, norepinephrine, neuropeptide Y and nociceptin.
These neurobiological bases of the anti-reward circuit can be related to some ideas discussed by Dean Burnett in his book “The Happy Brain” (2018). In that book he comments that several investigations have detected abnormally high levels of corticotropin in the cerebrospinal fluid of people who have committed suicide. Furthermore, it is also commented that Dynorphins have often been linked to negative emotions, stress and depression
Emotional regulator?
Dynorphin and corticotropin are two neurotransmitters that cause the opposite effect to euphoria, that is, dysphoria. These two substances present in the brain and involved in the anti-reward circuit induce negative emotions and anxious-depressive symptoms. Given that our brain has the neuronal bases for this system and that it is not something acquired or the product of a disorder or neuropathology, What adaptive function does this peculiar circuit have?
Added to this mystery, it is worth mentioning the fact that it seems that the anti-reward circuit is activated together with the reward circuit. That is, our brain activates two systems that seem to be antagonistic, which awakens even more mystery about why this system exists, since it means that we feel pleasure and dissatisfaction at the same time. Why does our brain need to activate two things that contradict each other?
The main function that the anti-reward circuit would have would be to regulate our mood. That is, when something activates our reward system, it is normal to feel satisfaction, euphoria and positive feelings, which if too exaggerated could translate into an episode of hypomania. To avoid this, the anti-reward system is activated by reducing pleasure, preventing us from getting too carried away and committing irresponsible acts
The other function would be to keep the reward system operational. In our body there are multiple systems that carry out various functions and that, to adjust and regulate, require an antagonistic system to act as a counterbalance. For example, the sympathetic and parasympathetic nervous systems perform opposing but coordinated functions that help the body maintain its homeostasis (e.g., inhibiting or stimulating digestive activity). If one of the two failed, our body would go into crisis and we could manifest diseases.
So that, the anti-reward circuit would act to ensure that the other system is functioning properly, in addition to regulating behavior and adaptations of the individual to certain behaviors, substances and environmental events. By activating one and making the other rest, the cells are kept alive, avoiding overstimulation of one of the systems and, consequently, the decay of the organism.
And when does the imbalance occur? Both the reward system and its counterpart are closely related to addictions. The balance that both systems maintain is compromised when drugs are consumed in excess. A key element of addictions is the development of a negative emotional state during withdrawal. The neurophysiological basis of this negative emotional state derives from two processes: on the one hand, a reduction in activity in the reward system, and on the other, increased activity in the anti-reward circuit.
When we have been consuming an addictive substance for a long time, be it tobacco, alcohol or simply caffeine, it is normal that we end up developing a tolerance to certain quantities. This means that to receive a kick, a “high”, we need to increase consumption. If we stop consuming suddenly or take less doses than our body is used to, we begin to feel negative emotions such as depression, apathy, irritability, in addition to other symptoms associated with withdrawal syndrome.
People addicted to substances have the problem that their reward system is no longer activated when consuming a certain amount of the drug, since it is hyposensitized. The problem is that if they stop taking the drug, since the anti-reward system is hypersensitized, if they do not take the drug or take less than they need, they begin to feel very bad, which makes them more prone to consume again to avoid suffering. This is one of the explanations for why addictions occur and how difficult they are to abandon.
It should be said that, although more and more research is being done on the anti-reward circuit, the hypotheses behind why its peculiar functioning and how it counteracts the effects of the reward system are very tentative. It is not known to what extent both systems, balanced, function in the brain of a healthy person without addiction, and it is also worth mentioning that the theories applied to people with drug dependence are in their infancy. Likewise, it seems that it is an emotional regulator, or more specifically, a satisfaction regulator.
