The human brain reacts almost instantaneously to certain stimuli considered threatening: parts of the brain such as the tonsil or the ventromedial prefrontal cortex would intervene in this “circuit of fear” that is responsible for protecting us at threats.

But what happens when our brain remains on alert for too long, when the stress response is too intense? Anxiety and depression disorders could be related to a Overload in the brain detection of threatening stimuli.

The fear circuit and stress response to the threat

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Breathing accelerates for provide more oxygen to The musclesthe heart rate rises to more effectively manage this oxygen, Adrenaline rises in the bloodthe skin becomes less sensitive by constraining the blood vessels of it so that there is the least possible bleeding in case of wound. In parallel, The immune system is also alertadhering the white blood cells to the walls of the blood vessels so that they are prepared at a possible injury.

This Physiological response in which different components of our body intervene is launched before the detection of a threat, and does so coordinated To prepare our body in a situation of great demand: it is the stress response to the threat.

Forks The brain who acts as director of this physiological orchestra. But, what part of the brain perceives the threat in the first place, which part feels fear before any other? Neuroscience puts the focus, first of all, in the amygdala that would act as a generator in this circuit of fear.

A study published in 2016 in the magazine Nature Neuroscience and in which professionals from several Spanish entities such as the Polytechnic University and the Clinical Neuroscience Laboratory, both in Madrid, intervened, both in Madrid, analyzed the fast or “shortcut” that sends an almost instantaneous response to the amygdalathe key area that would process fear and other primary emotions.

This almond -shaped mass that we have in the brain It is common to all mammals And it would have had a fundamental importance in the evolution of species, particularly in ours, being the critical structure involved in emotions: the tonsil would coordinate the primary responses to fear and would have “saved life” to numerous of our ancestors. As? Through the aversive memory storage that would depend on the modulation of the activity of the hippocampus by the amygdala.

That is, thanks to the intervention of various brain areas, For thousands of years the human brain and the rest of mammals is storing aversive memory and threatening stimuli so that it allows automatic reactions to those stimuli that our aversive memory considers potentially harmful.

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This is the reason why we react almost instantaneously and put ourselves on alert to certain situations, Like the presence of a poisonous animal. And this would be the explanation of some apparently indecipherable primary fears such as tripophobia.

This immediate response of the brain coordinated by the tonsil was analyzed by the aforementioned study published in Nature Neuroscience finding almost snapshot responses from the amygdala: This area reacted in 74 milliseconds – a reaction “ultra -grape”– To an alleged threat, recreated in the form of images with faces of fear exposed to the volunteers of the study.

However, and due to the location of the amygdala In the deep structure of the brain What complicates its analysis by common methods such as functional resonances, leads some experts to assess other brain areas in the management of threats and primary emotions such as fear.

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In this sense, the Ventral prefrontal cortexlocated above the eyes, it could also have a key role. And it is that the evolution of the human being has led us to a more sophisticated management of fear than other mammalsplacing each threat in context, allowing a more elaborate reaction in which more brain areas would intervene.

Thus, as this study points out, the ventromedial prefrontal cortex would react to negative visual events in approximately 100 and 150 milliseconds connecting its response with other regions responsible for relevant cognitive processes in making decisions on how to face a negative event, for example, it itself Planning of the response action to the stimulus.

Thus, that circuit of fear that puts us in relation to our ancestors and that would have evolved more sophisticated with respect to other mammals would be the maximum responsible for ensure our survival requesting a stress response to activate our body, as well as generate ultra -grape cognitive reactions.

But what happens when that stress response remains active for a longer time, When the alert level is sustained by a (supposed) threatening stimulus that does not disappear? Then the immediate physiological response that life would save us in a specific context can condemn us in another.

Chronic stress and continuous alert: When we see giants where there are only mills

Representation of the scene of Los Molinos de Don Quijote on a wall of tiles – Source: Depositphotos

The physiological response to a threat is of great demand for our physique, but also for our psychic facet. That is the reason why We feel a “downturn” after a situation of enormous stress. The body needs to recharge from energy, requires rest to recover from the maximum alert you have lived. We are not designed to live permanently in alarm.

However, in certain situations, our brain feels a permanent threat, even if it is not such. I may intervene our aversive memory in which a certain psychological trauma emergesa phobia to a more or less concrete situation or the appearance of cognitive biases that prioritize threatening stimuli against those who are not really.

Be that as it may, the stress response that supposed an adaptive advantage when it occurs for a short period of time, It turns against us when it becomes chronic stress.

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And this is how certain anxiety disorders that would be the consequence of the detection of a permanent threat that may exist or not from an objective point of view can arise: that is, We perceive the threat, but the threat does not exist outside us: Don Quixote giants.

What if a “short circuit” occurs in our fear circuit? How would our brain react to an overload in the detection of threatening stimuli? An article by neurologist Eduardo Benarroch can have the answer, in relation to the activity of the amygdala with various psychiatric disorders.

Thus, for example, anxious individuals They show a high activity of the amygdala in response to stimuli associated with the threat – as the fament face – but Also before stimuli not associated with threat. On the other hand, functional magnetic resonance studies suggest that the amygdala can be a substrate for the generation of negative affection that characterizes depression.

Thus, when the threatening stimuli proliferate, The brain could “disconnect” emotionally from realityto the point that the amygdala ceases to properly coordinate emotional responses so that positive or neutral events can be interpreted negatively: we are in the prelude to depression, Everything looks grayeven in the most “sunny.”