"Nature" During sleep, brain regions synchronize motor memories

When Golden State Warriors' Steph Curry makes a free throw, his brain uses motor memory
.
Now, researchers at the University of California, San Francisco (UCSF) have shown how this type of memory is consolidated during sleep, when the brain processes daytime learning, making the physical act of doing something subconscious
.

The study, published December 14, 2022 in the journal Nature, shows that the brain does this
by reviewing the trial and error of a given action.
Metaphorically, that means sorting through all the free throws Curry has made and erasing the memory of all actions, except those that hit the target or those that the brain thinks are "good enough
.
" The result is the ability to make free throws with great precision
, without taking into account the body movements involved.

Karunesh Ganguly, MD, professor of neurology at the Weill Institute for Neuroscience at UCSF, said: "Even elite athletes make mistakes, and that's where
the game is interesting.
Motor memory is not perfect
.
It's about foreseeable mistakes and foreseeable successes
.
As long as the error remains stable day after day, the brain says, 'Let's
lock up this memory.
'" ’”

Ganguly and his team found that the "lockdown" process, which involves some surprisingly complex communication between different parts of the brain, occurs during
deep restorative sleep known as non-REM sleep.
Sleep is important because our conscious brains tend to focus on failure, says Ganguly, who previously found that sleep-related brain waves affect skill retention
.
"During sleep, the brain is able to sift through all instances it accepts and suggest patterns
of success.
"

Motor skills on Earth don't work on the planet Pandora in Avatar, and it was once thought that learning motor skills only required the motor cortex
.
But in recent years, more complex situations have emerged
.

To dig deeper into the process, Ganguly asked mice to fetch food
.
The team then looked at their brain activity in three regions during non-REM sleep: the hippocampus, which is responsible for memory and navigation, the motor cortex, and the prefrontal cortex (PFC).

Over the course of 13 days, a pattern
emerged.

First, in a process known as "rapid learning," PFCs coordinate with the hippocampus, potentially enabling the animal to sense its movement relative to the surrounding space and its position
in that space.
At this stage, the brain seems to be exploring and comparing all the movements and patterns
produced while practicing tasks.

Second, in a process known as slow learning, PFC appears to make value judgments, which may be driven
by reward centers that are activated when the task succeeds.
It crosses with the motor cortex and hippocampus, turning off signals related to failure and turning on signals
related to success.

Finally, when the electrical activity in these regions becomes synchronized, the role of the hippocampus is weakened, and reward events recorded by the brain appear, which are stored in
what we call "motor memory.
"

When rats initially learned the task, their brain signals were noisy and chaotic
.
Over time, Ganguly could see signal synchronization until the rats reached a 70 percent
success rate.
After that, as long as the degree of success is stable, the brain seems to ignore the error and maintain motor memory
.
In other words, the brain begins to anticipate a certain degree of error without updating motor memory
.

Just like NBA players, rats have mastered a skill in mental models based on how the world works, created from physical experiences of gravity, space, and other cues
.
But this motor learning is not easily transferable to situations where
cues and physical environments are different.

"If everything had changed, for example, if Stephen Curry had been in the world of Avatar, he might have seemed less skilled at first
," Ganguly said.

The best way to break a habit

What if Curry hurts his finger and has to learn to shoot differently? This study provides an answer
.

"It's possible to forget a task, but to do that you have to emphasize the situation to the point
where you make a mistake," Ganguly said.

When the researchers made slight changes to the rats' task of acquiring pellets, the rats made more mistakes, and the researchers saw more noise
in the rats' brain activity.

This change is small enough that rats don't need to go all the way back to where they started where they started, just to the "breakpoint" and then relearn the task
from there.

But Ganguly said that because motor memory is a set of actions that follow each other in time, changing motion memory in a complex action, such as a free throw, may require changing an action
that initiates the entire sequence.

Ganguly said that if Curry usually bounces the ball twice before pitching, "it's best to retrain the brain
by only bouncing once or three times.
" This way, you can start from scratch
.
”