- Why do we keep only a tiny part of what we learn? The memory has not yet revealed all its secrets.
- Neuroscience, however, gives us more and more information about the functioning of our brain, especially the hippocampus, a key organ for memorization.
- Thanks to the sixth science podcast on memory and this interview with Géraldine Rauchs, researcher at Inserm, we are trying to find out a little more.
Why do we remember better holidays 25 years ago than yesterday? Neuroscience teaches us more and more about the mysteries of our brain and its development. On the occasion of the Sixth Science podcast, organized by 20 minutes in partnership with Science and Future, we wanted to know a little more about how the
memory, and in particular its links with the
Géraldine Rauchs, researcher at
Inserm and for the brain imaging platform
Cycéron, Caen, enlightened our lantern on memory, sleep … and
To listen to the episode of our Sixth Science podcast, "How to improve your memory?":
What are the phases of memory?
There are three: encoding, that is, learning information to create connections between different elements. Then comes the consolidation: this learning is stored in the long-term memory. It intervenes during waking, but is optimized during sleep. Third step is the reminder, for example the class control of the next day during which information must be highlighted.
How does sleep intervene in our memorization?
Initially, it was thought that there was only paradoxical sleep, during which one dreams, which was important for memorization. But studies have shown that deep slow sleep is also involved in learning. Deep slow sleep has long been opposed, important for episodic memory, that is to say all the information of the day, and REM sleep, which played a role for procedural memory, when one learns to ski. or violin. But in fact, today, we know that all stages of sleep are important for the different parts of our memory. If we disrupt the architecture of the sleep cycles, we disturb the learning.
You did a study on sleep deprived students. What can we conclude?
Students were taught to learn words to remember and forget. Some returned home for the night, others were deprived of sleep. The next morning, all the students came back to the lab, and we had a memory test. All these students had equivalent performances on the words to remember. On the other hand, paradoxically, those who had been deprived of sleep remembered more terms to forget than others. This is why sleep plays a considerable role in memorization: it consolidates the relevant information, but also eliminates those that are useless. Forgetting is often seen as a malfunction of our brain, but in fact, if we do not forget, we can not learn properly.
Can we boost our memory at night?
For now, these are only experiments in laboratory conditions that tend to show that sounds, electrical stimulations or smells reactivate the connections during sleep. From there to boost your memory during the night, which makes a lot of fantasy, we are not there! So listen to the recording of his course all night before an exam, for now, it does not work. Especially since it goes against the rules of hygiene of sleep. During certain stages of sleep, our brain is working, so it needs to be in a quiet environment.
You also focus your research on Alzheimer's disease, a subject obviously related to memory …
We work on the link between duration and quality of sleep and brain and cognitive impairment. What's new enough, but it's a hypothesis, is that sleep would cleanse the brain, which eliminates metabolic waste. This is a very interesting track for all neurodegenerative diseases, related to the accumulation of certain proteins in the brain. Maybe poor sleep increases the production of these proteins or prevents cleansing. And suddenly increases the risk of developing Alzheimer's disease.
Why is this research on sleep and Alzheimer's disease important?
For the moment, no effective drug has been found to control this disease once it has settled. Hence the importance of better prevention, especially in a context of aging population. Especially since one adult in two complains of his sleep! We test two techniques, imagery to support, to see if meditation on one side, learning a new language on the other, can improve the quality of sleep, and thus limit the impact of brain related to aging.
Why do older people who lose their memory forget more recent events than memories of their childhood?
When you live an event, the memory will be preserved after a long reorganization in your brain. Short-term memory solicits your hippocampus, a key structure of memory. It labels the memories but does not store them, it's the table of contents in a way. A memory will be stored in different areas of the brain: a smell in the olfactory cortex, an image in the visual cortex … During the consolidation of this memory, we will strengthen the connections between the different areas of the brain and we will no longer necessarily need to go through the hippocampus to reactivate it. In the case of Alzheimer's disease, the hippocampus is deficient, so we will remember more childhood than the visit of the neighbor the day before. A memory is better encoded when there is a strong emotion, positive or negative. Now, the beginning of adult life, its marriage, the birth of its children does not have the same emotional richness as the tea of the day before …