The human brain uses dreams to replay recent events and help form memories – and experts have had the first glimpse of this process in action, one study reported.
When we sleep, our brains replay the firing patterns that our neurons underwent when awake – a process that experts call “replay offline”.
Offline rereading is believed to underlie so-called memory consolidation, the way in which recent memories acquire a more permanent representation in the brain.
Although re-diffusion has been previously seen in animals, it has never been seen before in humans.
Using implanted electrodes, American researchers were able to show that people’s brains replay neural activity from a memory game while they sleep.
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The human brain uses dreams to replay recent events and help form memories – and experts have first glimpse of this process in action, study finds
The study was led by psychologist Jean-Baptiste Eichenlaub from Massachusetts General Hospital, neuroscientist Beata Jarosiewicz from BrainGate and colleagues.
BrainGate is a research consortium that works to develop implantable brain calculation interfaces, with the aim of helping people with severe motor disabilities to be able to mentally manipulate computer cursors, robotic arms and other devices.
“This is the first direct evidence that in humans we also see a replay during rest after learning which could help to consolidate these memories,” said Dr. Jarosiewicz.
“The study is unprecedented. All the mechanisms of memory consolidation linked to re-reading that we have studied in animals during all these decades could also be generalized to humans.
In their study, the team asked two participants to take naps before and after playing a sequence copy game – one similar to the 80s classic “ Simon ”, which included four colored panels that s ‘lit up in different patterns so players could repeat them.
Instead of hitting the colored panels with their hands, however, the volunteers were asked to play the game with their minds, instead – visualizing themselves by moving a cursor on a screen to select each colored target in turn as quickly as possible.
Throughout the experiment, the researchers used an implanted array of electrodes to monitor how the pair’s neurons got rich while they slept and played.
In their study, the team asked two participants to take naps before and after playing a sequence copy game – one similar to the classic 80s “ Simon ” illustrated, which included four colored panels. which were lit in different patterns so that players could rehearse.
“There are not many scenarios in which a person would have a multi-electrode array placed in their brain, where the electrodes are small enough to be able to detect the firing activity of individual neurons,” said the Dr. Jarosiewicz.
“This is why this study is unprecedented,” she added.
The electrodes approved for medical purposes – such as, for example, the treatment of epilepsy or Parkinson’s disease – are too large to be able to follow the activity of individual neurons.
However, those used in BrainGate’s experimental trials can record brain activity at a much higher resolution.
When they analyzed the neural data from the electrode implants, the team discovered that the study participants’ brains repeatedly displayed the same patterns of activity when they slept after play as they did when they slept. were playing.
This provided researchers with the first concrete evidence that offline replay occurs in our brains while we sleep like in animals.
With this initial study completed, the researchers said the next step would be to prove that offline replay has indeed a direct role in the process of memory consolidation.
This could be done, for example, by testing the relationship between the intensity of neural activity during offline replay with the strength of memory recall after sleep.
Either way, experts are convinced, from various previous animal and human tests, that sleep plays an essential role in learning and memory consolidation.
This is why getting a good night’s sleep “before a test and before important interviews” leads to better performance, said Dr. Jarosiewicz.
“We have good scientific evidence that sleep is very important in these processes.”
The full results of the study were published in the journal Cell reports.
HOW A FAMOUS AMNESIAC LEARNED US HOW WE FORM LONG-TERM MEMORIES
From the 1950s, studies of the famous amnesiac patient Henry Molaison revealed that the hippocampus is essential for forming new long-term memories.
Molaison, whose hippocampus was damaged during an operation to control his seizures, is no longer able to store new memories after the operation.
However, he could still access certain memories that had formed before the surgery.
This suggests that long-term memories of specific events are stored outside the hippocampus.
Scientists believe that these memories are stored in the neocortex, the part of the brain also responsible for brain functions such as attention and planning.