Surprise, fear, anguish, affection, love, joy, excitement… All these words denote different emotions that we all feel in our daily lives .

These are reactions that we have to stimuli that can come both from the outside (for example, seeing a spider, a baby, or being told about your long-awaited ascent) and from inside the person himself (a thought or memory that makes you suffer or feel happy). These reactions, at a cerebral level, depend on a series of circuits that are capable of organizing and connecting perception and emotion, the main system in charge of this being the limbic system, and within this system being the amygdala one of the main nuclei.

In this article we will focus on this structure, the amygdala, in order to visualize what it is and some of its main functions .

What is the amygdala?

The amygdala is a subcortical structure located on the inside of the medial temporal lobe . This element has connections with the vast majority of the brain, being a nucleus of special relevance that can affect the whole nervous system and the functionality of the organism.

It is a key element for survival, because its main function is to integrate emotions with the response patterns corresponding to them , provoking a response at a physiological level or the preparation of a behavioural response. Likewise, it is in charge of coordinating the areas that notice the somatic expression of the emotion and the cerebral cortex in charge of the conscious feeling, with which it has a very relevant role in the assessment of the emotional meaning of the experiences.

The amygdala is therefore the main control nucleus of emotions and feelings in the brain, controlling also the responses of satisfaction or fear. Its connections not only produce an emotional reaction but because of its link to the frontal lobe it also allows the inhibition of behaviour.

Now, the amygdala is not just a “piece” of the human brain, with a predictable and well-known pattern of functioning. In fact, none of the structures of the brain are like this, but in the case of the amygdala this is even more evident, bearing in mind that is related to many other areas of the central nervous system . It is a complex structure, being an almond-shaped structure located in the limbic system of the brain. It is configured by different parts, which is why it is sometimes also called an amygdalin complex.

Parts of the amygdalin complex

As we have said, the amygdala is not a uniform structure, but it is divisible into several subelements . Among them, the following stand out:

Corticomedial nucleus

This part of the amygdalin complex is heavily involved in pheromone uptake, participating to a large extent in the control of both male and female sexual behavior. It is also involved in hormonal control and the satiation response during ingestion.

Basolateral cores

Its main participation is in the control of intake through the feeling of satiety . Likewise, it is essential to involve them in the realization and learning of learned emotional responses, such as reactions to different stimuli.

Central core

This nucleus is the one that has the greatest participation in the expression of the emotional response , affecting both on a physiological level, producing the sensations and physical reactions that emotions provoke and having a great participation in the autonomic nervous system, as well as behavioural by allowing the performance of behaviours that respond to the sensations that perceptions produce.

Likewise, this nucleus also affects the genesis and maintenance of feelings, which differ from emotions in that they are thought patterns and psychophysiological reactivity maintained over time and less specific to a particular situation.

Functions of the amygdalin complex

As mentioned, the amygdala is a complex structure vital for survival, participating and being linked in a great number of psychological and physiological phenomena . Let us now look at some of them:

Integration of emotions and autonomous responses

The amygdala manages with great precision the emission or inhibition of emotional responses both at a conscious and unconscious level, its function being the most studied and one of the most relevant. It allows us to associate feelings of gratification or aversion to the experiences we live. It participates both in positive emotions such as reactions of joy or happiness and in other emotions of a more adaptive nature, as we will see in the next point.

2. Fear management and fight/run reaction

In this aspect, one of the main functions of the amygdala and the fact that it is a key part of survival is fear management . At a phylogenetic level, this nucleus has allowed the survival of our species, given that it is the one that allows us to react after perceiving a potentially threatening stimulus for physical integrity, stimulating or inhibiting the fight/run away response. In fact, lesions in the amygdala can cause extremely aggressive reactions and the loss of fear, with all the repercussions that the absence of this feeling can entail.

3.Emotional learning

Associative and conditioned learning is also largely influenced by the action of the amygdala . This structure allows the choice of strategies to be applied in the presence of stimuli, as well as detecting situations in which these strategies are also applicable. This is due to the link between emotion and cognition, as well as in the maintenance of motivation by linking the objectives themselves to specific feelings.

4. Memory

In addition to the learning process, the amygdala also affects the structuring of memories . This is due to the association of memories with emotional states, which allow a greater connection and fixation of the material to be remembered, allowing its consolidation.

In fact, even when the hippocampus fails to store certain memories, the amygdala allows a certain emotional recollection of a situation to be preserved, so it is possible, for example, to be very afraid of dogs (emotional memory) without remembering why this happened (because of the stress suffered in a traumatic event with a dog, that “narrative” memory of what happened has not been preserved).

5. Regulation of sexual behaviour

Sexual behavior is also influenced by the performance of the amygdala . In addition to allowing the association of different stimuli with pleasure, the emotional bond between individuals and their association with the maintenance of intimate relationships are due, among other structures, to the amygdala complex.

6. Aggressiveness

The amygdala is also linked to aggressiveness . The studies carried out to date indicate that a malfunctioning of the amygdala can lead to the loss of aggressive and self-defence reactions, while a hyperstimulation of the amygdala complex causes extremely aggressive and violent reactions.

7. Satisfaction response

Another aspect in which the amygdala has some influence is in the control of intake, contributing greatly to the maintenance of body homeostasis through its influence on the perception of satiation.

Bibliographic references:

  • Kandel, E.R.; Schwartz, J.H. & Jessell, T.M. (2001). Principles of neuroscience. Fourth edition. McGraw-Hill Interamerican. Madrid.
  • MĂ©ndez-BĂ©rtolo, C.; Moratti, S.; Toledano, R.; LĂłpez-Sosa, F.; MartĂ­nez-Álvarez, R.; Mah, Y.H.; Vuilleumier, P.; Gil-Nagel, A. & Strange, B.A. (2016). “A fast pathway for fear in human amygdala”, Nature Neuroscience.
  • Nieuwenhuys, Voogd & van Huijzen (2009). The Human Central Nervous System. 4th Edition. Editorial MĂ©dica Panamericana. Madrid.