Thanks to a unique system that decodes brain activity during sleep, a research team has succeeded in deciphering the neural mechanisms of memory consolidation.
- The researchers succeeded in decoding the brain activity during sleep of participants by combining artificial intelligence, MRI and EEG.
- They found that certain areas of the brain activate and communicate with each other during sleep, which strengthens the bond between neurons.
- They also found that our brain selected the “good” memories more, and that these were therefore more easily consolidated.
What does our brain do during the long hours we are asleep? It draws our dreams… But also consolidates our memory, reveals a new study conducted by scientists from the University of Geneva (UNIGE) and published in NatureCommunicationswhich for the first time opens a window into the dormant human mind.
A combination of artificial intelligence, MRI and EEG
The researchers explain that they have developed an artificial intelligence capable of decoding brain activity during sleep. By combining functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), it shows that during our deep sleep, our brain sorts through thousands of pieces of information processed during the day. During deep sleep, our brain no longer receives external stimuli and can evaluate all these memories to retain only the most useful. To do this, it establishes an internal dialogue between its various regions, in particular the hippocampus (the region of the brain that stores temporary traces of recent events) and the cerebral cortex.
To better understand this process, researchers have developed a decoder “able to decipher brain activity in deep sleep and what it corresponds to, explains Virginie Sterpenich, researcher and co-author of the study. In particular, we wanted to see to what extent positive emotions play a role in this process”.
To carry out their experiment, the scientists placed volunteers in an MRI in the early evening and had them play two video games: a face recognition game similar to “Who is that?” and a 3D maze to find the exit. These games were rigged without the knowledge of the volunteers so that only one of the two games could be won so that the brain associates the won game with a positive emotion.
The volunteers then slept in the MRI for one or two hours – the length of a sleep cycle – and their brain activity was recorded again. “We combined EEG, which measures sleep states, and functional MRI, which takes a picture of brain activity every two seconds, and then used a neural decoder to determine whether the observed brain activity during the game period reappeared spontaneously during sleep”explains Sophie Schwartz, who led the work.
Memorized rewards during sleep
By comparing MRI scans of the waking and sleeping phases, the scientists observed that during deep sleep, patterns of brain activation were very similar to those recorded during the gaming phase. “And, very clearly, the brain was reliving the game won and not the game lost by reactivating the regions used during wakefulness. As soon as we fall asleep, the brain activity changes. Gradually, our volunteers began to ‘think ‘ to both games, then almost exclusively to the game they won when they went into deep sleep”explains Virginie Sterpenich.
Two days later, the volunteers performed a memory test on the two games. Again, the more gaming-related brain regions were activated during sleep, the better the memory performance. Thus, reward-associated memory is higher when spontaneously reactivated during sleep. With this work, the Geneva team opens a new perspective in the study of the sleeping brain and the incredible work it does every night.
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