A team of scientists from the University of Zurich and the Swiss Federal Institute of Technology in Zurich, both in Switzerland, examined the effect of poor sleep and insomnia on the brain’s ability to learn new things.
The study – published in the journal Nature Communications – looks at the brain’s ability to change and adjust in response to the stimuli that it receives from the environment in the motor cortex and how it is affected by deep sleep.
The motor cortex is the brain area responsible for developing and controlling motor skills, and the deep sleep phase is important for memory formation and processing, as well as for helping the brain to restore itself after a day of activity.
Manipulating the motor cortex during deep sleep
The study involved six women and seven men who were asked to perform movement tasks during the day following a night of uninterrupted sleep, and after a night during which their deep sleep had been disturbed.
The tasks involved learning a series of finger movements, and using an electroencephalogram, the scientists monitored the brain activity of the participants while they were sleeping.
On the first day of the experiment the participants were able to sleep without disturbance.
On the second night, however, the researchers manipulated the participants’ sleep quality. They were able to focus on the motor cortex and disrupt their deep sleep. The participants did not know that their deep sleep phase had been tampered with. To them, the quality of their sleep was about the same on both occasions.
Poor sleep keeps the brain connections excited, blocks the brain’s ability to learn
Next, the researchers evaluated the participants’ ability to learn new movements. In the morning, the subjects’ learning performance was at its highest, as expected.
However, as the day progressed, they continued to make more and more mistakes. Again, this was expected.
After a night of good sleep, the participants’ learning efficiency spiked again. But after their night of poor sleep, their learning efficiency did not improve as significantly, and performance was in fact as low as on the evening of the previous day.
The reason this happens, according to the researchers, is that during the manipulated deep sleep, the neurons’ synapses did not “rest” as they normally would during restorative sleep.
During the day, our synapses get excited as a response to the stimuli that surround us. During sleep, however, these synapses relax and restore themselves, and their activity “normalizes.” Without this, learning new things is no longer possible.
“In the strongly excited region of the brain, learning efficiency was saturated and could no longer be changed, which inhibited the learning of motor skills,” explains co-lead author Nicole Wenderoth.
This is the first time that a study has proven the causal connection between deep sleep and learning efficiency.
Reto Huber, professor at the University Children’s Hospital Zurich and of child and adolescent psychiatry, comments on the significance of the study:
“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.”