Tuesday, December 7

Discover the brain circuits that control responses to fear

Discover the brain circuits that control responses to fear

Discover the brain circuits that control responses to fear

A new study by scientists at the Sainsbury Wellcome Center at University College London has identified a series of brain circuits that can control responses to fear. The mechanism manages to nullify or enhance the defense instincts in the face of a potential threat, according to previous experiences or knowledge and the analysis of the current situation. It could be useful for new treatments for anxiety and post-traumatic stress.

According to a Press release, research has succeeded in determining that certain brain circuits in the ventral lateral geniculate nucleus (vLGN), an inhibitory structure found at the entrance to the thalamus and important to visual systems, can function as fear regulators. Although the study is based on rodents, it could have important implications for understanding the same mechanisms in humans.

Responses to fear

When we act in a dangerous situation or we feel threatened, usually two aspects come into play that determine our responses. On the one hand, if we live similar situations in the past and what record do we have of those experiences. And, at the same time, what assessment do we make of the apparent danger at the precise moment in which we go through it.

A combination of these two pieces of information, received mostly from the senses and from memory, will end up helping us decide whether to remain calm, flee, seek help, or prepare to defend ourselves from an attack. Now, a new study published recently in the journal Neuron has discovered what the brain circuits that are activated or extinguished when facing these kinds of situations.

Fear neurons

By subjecting rodents to a simulated threatening experience, which consisted of casting a giant shadow over them, pretending the arrival of a possible predator, they observed that a group of vLGN neurons they were in charge of coordinating the responses of the animals. In some situations they favored the development of defensive attitudes, while in others they promoted their cancellation.

The identification of this mechanism could be achieved by techniques of optogenetic stimulation, which consist of the use of light-sensitive ions to allow the activation or inhibition of certain neurons, making it possible to manipulate neuronal activity in real time.

In general terms, the researchers verified that when the activity of the vLGN neurons Mice were more likely to seek safety and escape perceived danger. On the contrary, if the indicated neurons were activated, the escape responses were completely neutralized in the face of imminent threats.

Related topic: They discover how the brain regulates fear.Related topic: They discover how the brain regulates fear.

Applications in psychosocial disorders

Specialists believe that vLGN works as a “Inhibitory gate”, establishing a threshold that motivates the greater or lesser sensitivity to a threat or danger, depending on the knowledge of the animal. If the rodent underwent similar traumatic experiences or feels that the current threat is strong and real, the inhibitory mechanism will kick in, the vLGN neurons will suppress their activity, and the animal will take a defensive attitude.

In the future, scientists believe their discovery may shed light on disorders such as anxiety or post-traumatic stress disorder, in which the feelings of danger and the afraid they are oversized until they negatively impact the quality of life of those affected. They even think that it could be possible to develop new treatments for these pathologies, which act on the identified brain mechanisms.


Flexible inhibitory control of visually evoked defensive behavior by the ventral lateral geniculate nucleus. Alex Fratzl, Alice M. Koltchev, Nicole Vissers, Yu Lin Tan, Andre Marques-Smith, A. Vanessa Stempel, Tiago Branco and Sonja B. Hofer. Neuron (2021).DOI:https://doi.org/10.1016/j.neuron.2021.09.003

Video: Sainsbury Wellcome Centre / YouTube.

Photo: Alexander Krivitskiy en Unsplash.


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