The brain’s anti-reward circuit: what it is and how it works

Let's see what the brain's anti-reward circuit is like and what it is for.

In neuroscience, the idea of the reward circuit is widely known. It is the neurological basis behind the performance of pleasurable behaviors, playing an important role in the development of addictions.

However, it seems that there is a similar and contrary mechanism, a set of brain areas that are involved in producing unpleasant sensations when performing a certain behavior.

This set of areas has been termed the anti-reward circuitry and, although it must be said that research is still being done on which areas are involved and what exactly they are used for, we are going to talk about this peculiar mechanism.

The anti-reward circuit

One of the best known concepts in neurophysiology is the idea of the reward circuit. This consists of a set of brain mechanisms that are attributed with associating certain situations with sensations of pleasure.

Thus, the brain learns to associate certain situations with sensations of pleasure, 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 produce pleasure, being a very important neurological component in motivation.

As a counterpart to this system, it has been proposed the existence of another circuit whose function would be to serve, in one way or another, as a regulator of behavior and mood. This is the anti-reward circuitry, which consists of a network of brain regions that give rise to negative physical and emotional emotions to certain events, substances and behaviors. In other words, in the same way that the reward system makes us feel pleasure, the anti-reward system makes us feel unhappy or, at least, less satisfied.

Neurophysiological basis

The idea of the anti-reward circuit is quite recent, and this is evidenced by the fact that to date little is known about how it works and which specific areas are involved in its activation. However, some brain regions that are suspected to be involved are known, as well as other biochemical bases that could explain its 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, other neurotransmitters 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 elevated levels of corticotropin in the cerebrospinal fluid of people who have committed suicide. In addition, it also comments 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, i.e. 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 neural basis for this system and that it is neither acquired nor the product of a disorder or neuropathology, what is the adaptive function of this peculiar circuit? what is the adaptive function of this peculiar circuit?

Adding to this unknown is the fact that it seems that the anti-reward circuit is activated together with the reward circuit. In other words, our brain activates two systems that seem to be antagonistic, which arouses even more mystery as to 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 of the anti-reward circuit 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 taking too much revenge and committing irresponsible acts..

The other function would be to keep the reward system operational. In our organism there are multiple systems that carry out various functions and which, in order to adjust and regulate themselves, need an antagonistic system to act as a counterbalance. For example, the sympathetic and parasympathetic nervous systems perform opposite but coordinated functions, which help the organism to maintain its homeostasis (e.g., inhibit or stimulate digestive activity). If one of the two were to fail, our organism would enter into crisis and we could manifest diseases.

Thus, the anti-reward circuit would act to make sure that the other system functions properly, as well as regulating the individual's behavior and adaptations to certain 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 the 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 overused. 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 tolerance to certain quantities. This means that in order to get a kick, a "high", it is necessary to increase consumption. If we stop using suddenly or take less dosage 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.

People addicted to substances have the problem that their reward system is no longer activated when consuming a certain amount of the drug, as it is hyposensitized.because it is hyposensitized. The problem is that if they stop taking the drug, as the anti-reward system is hypersensitized, in case they do not take the drug or take less than they need, they start to feel very bad, so they are more likely to use again to avoid suffering. This is one of the explanations why addictions are so difficult to quit.

It must be said that, although more and more research is being done on the anti-reward circuit, the hypotheses behind why it works in a peculiar way 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, non-addicted person, and it is also worth noting that 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.