Most of us know that a good night’s sleep is crucial to happiness and productivity and, conversely, a bad night’s sleep can have negative effects on our daytime results. Yet a new research manages to identify precisely the region of the brain that is responsible for learning new skills and shows how poor sleep quality can impact it.
A team of researchers from the University of Zurich (UZH) and the Swiss Federal Technology Institute (ETH) in Zurich, both in Switzerland, set out to investigate the impact of a disrupted deep sleep period on the brain’s ability to learn new information.
More precisely, the latest research – published in the journal Nature Communications – looks at the capacity of the brain to alter and adjust in response to the feedback it receives from the environment, or neuroplasticity, in the motor cortex and how deep sleep affects it.
The motor cortex is the brain region responsible for learning and regulating motor skills, and the deep sleep period-also known as slow-wave sleep-is essential to memory development and recovery as well as helping the brain recover after a day of activity.
Manipulating the motor cortex during deep sleep
The research included six women and seven men who were asked to perform motor activities during the day after a night of unperturbed sleep, and after a night that had disrupted their deep sleep.
The tasks included studying a series of finger motions and the researchers were able to precisely identify the region of the brain that was responsible for understanding motion.
The researchers tracked the participants ‘brain activity as they were sleeping using an electroencephalogram.
The participants were able to sleep without interruption on the first day of the experiment-after the first movement learning session.
But the researchers manipulated the sleep quality of the participants on the second night. Researchers have been able to concentrate on the motor cortex and interrupt their deep sleep, exploring the effect that bad sleep has on the neuroplasticity involved in the development of new motions.
The participants did not realize that they had tampered with their deep sleep process. For them the consistency of their sleep on both occasions was approximately the same.
Poor sleep keeps synapses excited, blocks the brain’s ability to learn
First, the researchers measured the willingness of participants to learn new moves. As predicted the learning output of the subjects was at its best in the morning.
They managed to make more and more errors as the day progressed though. This has been anticipated, once again.
After a restorative sleep night the learning performance of the participants increased again. But their learning performance hasn’t changed as dramatically after their night of controlled sleep. In reality, the morning after a manipulated sleep night the output of the participants was as low as on the previous day’s evening.
According to the researchers, the reason this occurs is that during the induced deep sleep the synapses of the neurons did not “rest” as they usually would during restorative sleep.
Our synapses get excited in the course of the day as a reaction to the stimuli that surround us. However, during sleep, these synapses repair themselves and “normalize” their behavior. Without this restorative time, the synapses remain excited to the limit for too long. Such a state inhibits neuroplasticity, meaning it’s no longer possible to learn new things.
“Learning output was concentrated in the highly excited area of the brain and could no longer be modified, which hindered the learning of motor skills,” explains co-lead author Nicole Wenderoth, professor at the ETH Zurich Department of Health Sciences and Technology.
The researchers repeated the experiment by performing the same assignment but stimulating a different region of the brain to ensure they found the correct brain area responsible for deep sleep.
Which resulted in no changes to the performance of the participants.
This is the first time a study has shown the causal link between deep sleep and the efficacy of learning.
Reto Huber, professor at University Children’s Hospital Zurich and child and adolescent psychiatry professor at UZH, commented on the study’s significance:
“We have developed a method that lets us reduce the sleep depth in a certain part of the brain and therefore prove the causal connection between deep sleep and learning efficiency […] Many diseases manifest in sleep as well, such as epilepsy. Using the new method, we hope to be able to manipulate those specific brain regions that are directly connected with the disease.”