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They discover how the brain regulates fear

07/19/2021 at 5:38 PM CEST

Scientists from the University of Bern and the Friedrich Miescher Institute in Basel have identified a group of neurons located in the central amygdala that are capable of regulating our responses to fear. Under certain conditions, they can reduce the negative impact of fear, which leads to various psychosocial disorders, such as anxiety.

The afraid It is a primary emotion that is generated in the presence of a possible danger, and that in certain situations can be positive to keep us safe. However, it can also be motivated by distorted perceptions of reality, which produce extreme anguish without a real and concrete basis. In these cases, the person can fall into deep anxiety attacks and even reach depression.

In Europe, about 15 percent of the population is affected by anxiety disorders, generated from exaggerated responses to fear that cause trauma, stress and other psychological problems. Therapies are often ineffective, because a detailed neurobiological understanding of fear and its consequences is lacking.

The role of the amygdala

Now, the Swiss researchers in charge of the new study have found that neurons in the central amygdala They are highly adaptable and essential for suppressing fear: they form neural microcircuits that can amplify or reduce responses related to fear, such as stress or anxiety.

The brain amygdala is made up of a set of neurons deeply related to each other: they act as a whole and give rise to an anatomically differentiable structure. Its shape is similar to an almond and it integrates the limbic system, a group of structures that direct emotions and behavior.

Although it is already known that the amygdala plays a central role in emotional responses such as fear, the specific neurons that could stop it and in the area of ​​this structure in which they were located had not been identified so far. The discovery provides further insight into the brain mechanisms underlying fear-induced responses.

Related topic: We get to the brain core of fear.

Neurons in dispute

In the research, which was published in the journal Nature Communications, specialists studied the system of Neural “showdown” regulating fear: a “push and pull” mechanism by which some neurons activate the feeling linked to fear and others suppress it. When the system works in harmony, fear only appears when it is really necessary, but problems arise if the mechanism becomes unbalanced.

According to a press release, scientists found in animal models that there are neuronal microcircuits “specialized” in fear in the central area of ​​the amygdala. If these circuits are repressed or overridden, they lead to long-lasting and pathological fear behavior. However, when they are activated, the behavior returns to normal and fear only appears if necessary.

The researchers made this discovery through a technique called optogenetics, which makes it possible to control some neuronal reactions by applying pulses of light. In this way, they were able to identify a population of neurons within the central amygdala that generates a specific enzyme, destined to regulate sensations linked to fear.

Taking into account that in humans the imbalance of this system can lead to psychosocial illnesses such as anxiety or panic attacks, the next step for this group of specialists will be to check whether the mechanism verified in animals can be transferred to the human environment. If so, you could initiate a series of new, more effective treatments against this type of pathologies.

Reference

Central amygdala micro-circuits mediate fear extinction. Nigel Whittle, Jonathan Fadok, Kathryn P. Macpherson, Robin Nguyen, Paolo Botta, Steffen BE Wolff, Christian Müller, Cyril Herry, Philip Tovote, Andrew Holmes, Nicolas Singewald, Andreas Lüthi and Stephane Ciocchi. Nature Communications (2021) .DOI: https: //doi.org/10.1038/s41467-021-24068-x

Photo: Alexandra Gorn on Unsplash.

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