Dreams and nightmares are useful for the brain
For neuroscientists, dream activity allows us to digest emotions.
Why do we dream? Can our brain make false memories from our dreams? How can we explain that even the most improbable things seem real during our sleep ? It was at the end of the 1950s that a French researcher, Michel Jouvet, identified a particular state in sleepers that he called paradoxical sleep : “It is obvious that our state resembles an awakening, because of the activation cortical which simulates a true active awakening: it would then be a paradoxical awakening since the threshold of awakening increases!”, he says in On Science and Dreams, Memoirs of a Oneirologist (Odile Jacob, 2013). The brain wakes up while the sleeper remains asleep; the situation is indeed paradoxical.
The explanation of this curious mechanism is today provided by very detailed brain imaging studies which make it possible to observe the brain in action. In fact, while some brain regions wake up, others remain deeply asleep. Awake, for example, the image-producing areas of the brain, which explains the very visual nature of dreams. Sleeping, on the other hand, are the structures responsible for placing objects in their context, which can generate scale aberrations (giant strawberry, city in a suitcase, etc.).
“The Guardian of Sleep”
Anomalies which are not necessarily surprising for the dreamer because the parietal and frontal cortex, involved in critical thinking, are deactivated during dreams. In the same way that the sounds perceived by our ears will not necessarily justify the activation of the brain's alert system as long as they are habitual and considered harmless. So, after one or two nights, the church tower no longer wakes up the newcomer to the village. “During paradoxical sleep,” explains Professor Martin Desseilles, who heads the medical psychology department at the University of Namur (Belgium), “a relative quiescence of the attentional network can explain why external stimuli delivered at this moment are either ignored or automatically incorporated into the dream narrative, instead of interrupting the story. Which suggests that dreams are the guardians of sleep.”
But for Professor Ernest Hartmann, the function of dreams is much more fundamental. The dream allows us to assimilate the emotions felt during the waking state. A bit like a piece of white modeling clay that needs to be kneaded so that it blends into a ball already full of different colors. The multi-colored ball representing the unity of emotional thought. “Connections are not made randomly. They are guided by the emotions of the dreamer,” he explains in The Nature and Functions of Dreaming (Oxford University Press, 2011). When an image arouses a strong emotion, which can be repeated from one dream to another, it does not translate, as Freud thought, the expression of a desire, but, according to Hartmann, "the expression emotional concerns of the dreamer.
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