DECRYPTION – Feelings, especially the most intense ones, occur at all stages of memorization. Fear is the most “efficient” for remembering an event.
Do you remember that day when, on a bicycle, a car almost ran over you? Even if it was a long time ago, there is a good chance that the fear felt has fixed in you the memory of the incident. Strong emotions are real memory anchors, contrary to what we thought for a long time. In the 19the century, the first experiments conducted to decipher the mechanisms of memory thus sought to isolate it from any emotional contingency. Yet life is rarely a long calm river: it is punctuated by sad, tragic, or happy events. Today, proof is made that from sadness to joy through anger, fear, disgust or surprise, emotions impact all memorization processes, from formation to memory recall.
To appreciate this power, one need only delve into In Search of Lost Time, by Marcel Proust. “We often take the impressions related by the writer as an example of the direct reactivation of memories by sensory impressions, explains Francis Eustache, director of a research unit dedicated to the study of human memory in Caen. But it’s much more complicated. Memory is built around a particular feeling, an indefinable emotion…” As the neurologist Catherine Thomas-Antérion explains, it is an emotional context, the attention of a loving mother offering him tea to warm him up that launches the narrator on the trail of a sweet episode in his life. The sip mixed with the crumbs of the cake makes it “twitch”, gives him a feeling of “delicious pleasure”, and off he went in search of other scraps of memory.
These privileged links between memory and emotions are first explained by the anatomy of our brain. “Emotions are managed in brain regions located just next to the hippocampus, a structure that is the obligatory passage point for memory. “Comments Véronique Lefebvre des Noëttes, psychiatrist for the elderly in Limeil-Brévannes (AP-HP). More precisely, in addition to the hypothalamus (in charge of vital functions such as hunger, thirst or temperature regulation) and the anterior cingulate cortex (with a key role in the evaluation of emotions) which prove to be necessary for the expression of emotions, these are also and above all managed by the amygdala, a small almond-shaped structure which adjoins the hippocampus. “Faced with a situation charged with emotions, the amygdala “tells” the hippocampus that it is important, that it must be memorized! » summarizes Francis Eustache.
Intense memories and stimuli
Thus, we remember much better a story or a detail that disgusted us or on the contrary delighted us than a fact without emotional impact, as many experimental studies have shown: it has been shown , for example, that we retain more words charged with emotions (for example, gift, caress, etc.) than neutral words (scissors, paper, etc.), which activates the amygdala and hippocampus more. But the researchers also found that this facilitation was all the more pronounced when the emotion associated with the stimulus was intense – knowing that it is more often when it is negative.
“In reality, this is only valid up to a certain threshold of emotions, tempers Professor Eustache, because at a level that is too strong and traumatic, the effect is on the contrary disturbing. » In the case of a dramatic event, the encoding of the event can be distorted: the victim of a knife attack will, for example, focus his attention on the weapon pointed at him, and will not print in his memory the face of his attacker. But the impact of emotions can also relate to the consolidation stage of a memory: several days after a given situation, we remember it much better if it frightened us or made us happy than if it left us of marble.
The researchers explain it by the fact that we talk more to those around us about a story that made us shudder with fear or pleasure. At the biological level, this translates into a clever concert between stress hormones, amygdala and hippocampus. A cheerful or disturbing scene will activate the amygdala, then the sympathetic nervous system, and hence the adrenal glands which produce several stress hormones, which in turn stimulate the vagus nerve, then the amygdala, which acts on the hippocampus , and consolidates the memory. This can be verified experimentally: when the influence of norepinephrine (stress hormone) is blocked by a drug (Propranolol) in volunteers, prior to a task where they are asked to memorize an aggressive or neutral story, they don’t remember one better than the other.
Violent stress and memory flies away
If the memories imprint all the better that they are associated with strong emotions, there is a limit beyond which everything changes: from a certain level of activation by the amygdala, the hippocampus is completely inhibited. And if the emotions leave traces that can be reactivated by a sensory stimulus, the contextual elements of the memory will be difficult to access: we will be unable to give details of the scene of an attack, the people who were present, etc.
This retrieval of memories is the last step in which emotions intervene, and as Francis Eustache points out, “we tend to remember more positive events than negative events. It is about consolidating a good self-image”. Such an inclination is even more pronounced in older people, provided they do not suffer from depression or post-traumatic stress disorder. In both cases, the poor self-image leads to focusing on negative events. As for the conscious recall of the details of a traumatic memory, it is difficult, even though this memory may resurface in the form of flashbacks or nightmares which bring the threat back to life in the present.