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Engrams: the traces that experiences leave us in the brain

Engrams: the traces that experiences leave us in the brain

May 4, 2024

We suffered a traffic accident, crashing into our vehicle a red car. This accident generates a series of injuries that we end up recovering from, but at the cost of great suffering and anxiety. The day comes when we pick up the car again, and we notice that in front of any red car, we shudder and get very nervous. The reason for this fact, to the majority, is logical. However, what is not so well known is what generates it at the brain level.

That is, we know that various neurons will be activated that will generate different effects, largely mediated by the limbic system. But how exactly do these neurons relate to react in a concrete way to situations similar to experiences already lived? In this sense there are neural circuits that are formed throughout development and life, and that after forming remain more or less stable: we are talking about the engrams .


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Engrams: what are we talking about?

We understand engram to that stable neuronal structure generated by the stimulation, be it external or internal, and that is linked to the activation of concrete responses are unconscious or conscious. The engram is the group of neurons, or neuronal circuit, which is activated by the perception of certain information .

Another frequent term to refer to this type of structure is the neuronal loop. In summary, it could be understood as the biological basis of a trace or scheme of operation derived from experimentation, such as the set of brain changes resulting from learning and what we memorize. It would be the process of forming concrete neural connections that when activated they reproduce the subjective experience that generated the fact that gave them origin.


The engrams can be both sensory and motor, being in them the basic programming of how to perceive or act upon stimulation. Both may be related. Although the formation of engrams is unconscious, these structures generate and influence both conscious and unconscious processes. They can trigger the generation of thoughts, emotions, movements or activation of physiological mechanisms.

In our brain there are a lot of these structures, the engrams being generic neural structures that participate in a large number of mental and physiological functions . It is a system that generates the synaptic facilitation and connection between different neurons, generating a closed circuit that reacts to the stimulation, awakening in turn other engrams that react and generate different responses.

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Training and psychobiology

The formation of engrams occurs before the coding of the experience and the neuronal activation that it generates. Repeated exposure to certain stimulation or derivatives of this causes neurons or specific nerve pathways to be activated consistently. The information that assets can come from very different ways or sensory modalities.


At the cellular level, the axon of the presynaptic neuron generates the excitation of the postsynaptic neuron repeatedly, which in the long run generates a change in both in such a way that the efficiency of its intercommunication is improved. It also allows more synapses to be established , reinforcing the circuit and connecting with other loops that generate a response to the stimulation.

At the level of neurotransmitter, the communication of neurons that are part of an engram is mainly performed by acetylcholine, although other hormones such as noradrenaline also have some effect.

However, it is necessary to take into account that the engram is fixed it is considered necessary that there is an activation of the limbic system , especially those regions linked to motivation, due to the need to give importance to a fact in order to generate automatisms.

Your role in memory

Engrams have an important role in storing information in a stable manner and remembering previous information: these are stable neuronal structures, which are going to be activated in a certain way and will continue to function in the same way unless changes or births are introduced new synapses

They are fundamental when it comes to allowing the storage of memory , being then the biological basis on which is sustained, for example, the repetition of certain behaviors or ways of reacting to certain situations. Engrams make us sensitive to specific stimulations and make it easier for them to react to them in previously learned ways.

This, for example, causes a person who has suffered some kind of aggression or abuse to have generated changes that cause similar stimuli (for example, the physical contact of someone of the sex of the attacker, although the person who is approaching us is not attacking us. and do not have bad intentions) may react with fear or defensiveness.

Not for that reason we are saying that all engrams correspond to negative or traumatic experiences, but also to those that generate very positive emotions. For example, a child ends up generating engrams that relate to the maternal or paternal figure with feelings of security and protection, which is why he may feel bad if they are not there or look for his closeness in case of discomfort.

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Not only in memory

So far we have mainly talked about the engram as a brain circuit linked to learning and memory . But the truth is that the engrams are not limited to that sphere: if we think of engrams as brain circuits that are activated by information, aspects such as perception, motor skills (how to walk for example), knowledge (including theory) of the mind), language, experience and emotional expression are also determined (although modifications and changes can be introduced) by these structures.

Bibliographic references

  • Cardinali, D.P. (1992). Manual of Neurophysiology. Ediciones Diaz de Santos, S.A. Madrid Spain.
  • González, J.L. (1987). Structure and function of the human mind. Psyche, 346 (8).
  • Lashley, K.S. (1950). In Search of the Engram, Symp.Soc.Exp.Biol., 4: 454-482.
  • Montserrat, J. (s.f.). Neural engrams and theory of the mind. Autonomous University of Madrid. Madrid Spain.

How We Make Memories - Crash Course Psychology #13 (May 2024).


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