Science has not been able to determine why we need sleep and why we die if we are deprived of sleep, but what it has proven are the many benefits of restful sleep to enjoy good health and prevent diseases, from obesity to dementia, among many others. Sleeping well is also key to mental health and emotional well-being, and now a group of scientists from the University of California San Francisco (UCSF) have shown that motor memory – associated with our abilities to perform a task – is consolidated during sleep. sleep when our brain processes what we have learned during the day to make the physical act of doing something subconscious.
The example that researchers have given to better understand this phenomenon is that when Steph Curry of the Golden State Warriors – a professional basketball team in the United States – scores a free throw, his brain resorts to motor memory and, according to their findings, the brain does this by reviewing the trial and error of a given action. In the analogy, that means sorting out every free throw Curry has ever taken, deleting the memory of all actions except those that hit the mark, or that the brain deemed “good enough.” The result is the ability to take the free kick with a high degree of accuracy without having to think about the physical movements involved.
“Even elite athletes make mistakes, and that’s what makes the game interesting,” said Dr. Karunesh Ganguly, a professor of neurology and a member of the UCSF Weill Institute for Neurosciences. “Motor memory is not about perfect performance. It’s all about predictable misses and hits. As long as the errors are stable from day to day, the brain says: Let’s block this memory.
Like the NBA players, the rats mastered a skill based on a mental model of how the world works, which they developed from their physical experience.
What these researchers have discovered is that the “locking-in” process involves surprisingly complex communication between different parts of the brain and takes place during deep restorative sleep known as non-REM sleep. Sleep is important because our conscious brains tend to focus on mistakes, said Ganguly, who had previously identified sleep-associated brain waves that influence skill retention. “During sleep, the brain is able to filter the information it has received and present the patterns that were successful,” he said.
How motor skills are learned
Before it was believed that learning motor skills only depended on the motor cortex, but it has since been observed that it is something more complex. Ganguly’s team wanted to closely observe this process and gave rats the task of reaching for granules while they studied their brain activity in three regions during non-REM sleep: the hippocampus, the area responsible for memory and navigation, the cortex motor and prefrontal cortex (PFC), a region associated with planning cognitively complex tasks.
They first verified that, in a process called “rapid learning”, the PFC coordinated with the hippocampus, which probably allowed the rodent to perceive its movement with respect to the space around it and its location in said space. The brain seemed to be exploring and comparing all the actions and patterns created while performing the task.
Second, in a process called slow learning, the PFC appeared to make value judgments, likely driven by reward centers that kicked in when the task was successful. It engaged in crosstalk with the motor cortex and hippocampus, turning down signals associated with failures and increasing those associated with successes. Finally, as the electrical activity of the areas became synchronized, the role of the hippocampus was reduced and the requests that the brain had marked as rewarding came to the fore, where they were stored in what we call “motor memory”.
At first, when the rats were learning the task, their brain signals were disorganized, but as time went on the researchers were able to watch the signals sync up, until the animals got it about 70% of the time. After that point, the brain seemed to ignore the errors and maintained the motor memory while the level of success remained stable; that is, the brain begins to expect a certain level of error and does not update motor memory.
The study, which has been published in Nature, has shown that, like NBA players, the rats mastered a skill based on a mental model of how the world works, which they developed from their physical experience with gravity. , space and other signs. However, this type of motor learning would not easily transfer to a situation where the signals and the physical environment were different. “If all of that were to change, for example, if Steph Curry was in the world of Avatar, he might not seem so skilled at first,” Ganguly notes.
The researchers posed the question: What if Curry hurt his finger and had to learn to shoot baskets a little differently? And they found an answer: “It is possible to unlearn a task, but to do that, you have to stress the situation to the point where you are making mistakes,” explains Ganguly. So when they introduced slight variations to the rats’ pellet-getting task, the rats made more errors and the scientists saw more noise in the animals’ brain activity, even though the change was so minimal that the rodents didn’t have to go back to the beginning. beginning of your learning, but only to the “breaking point” and relearning the task from there.
Ganguly points out that because motor memory is established as a set of movements that occur over time, changing motor memory in a complex movement like throwing a basketball may require changing a movement that is used to initiate the entire sequence. . If Curry usually bounces a basketball twice before shooting it, according to Ganguly: “It would be better to retrain the brain by just bouncing it once or three times. That way, you’d start from scratch.”
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