Deep sleep maintains the learning efficiency of the brain

May 22, 2017, University of Zurich
Credit: CC0 Public Domain

For the first time, researchers of the University of Zurich and Swiss Federal Institute of Technology in Zurich have demonstrated the causal context of why deep sleep is important to the learning efficiency of the human brain. They have developed a new, non-invasive method for modulating deep sleep in humans in a targeted region of the brain.

Most people know from their own experience that just a single sleepless night can lead to difficulty in mastering mental tasks the next day. Researchers assume that deep sleep is essential for maintaining the learning efficiency of the in the long term. While we are awake, we constantly receive impressions from our environment, whereby numerous connections between the nerve cells - so-called synapses - are excited and intensified at times. The excitation of the synapses does not normalize again until we fall asleep. Without a recovery phase, many synapses remain maximally excited, which means that changes in the system are no longer possible: Learning efficiency is blocked.

Causal connection between deep sleep and learning efficiency

The connection between deep sleep and learning efficiency has long been known and proven. Now, researchers at the University of Zurich (UZH) and the Swiss Federal Institute of Technology (ETH) in Zurich have been able to demonstrate a causal connection within the human brain for the first time. Reto Huber, professor at the University Children's Hospital Zurich and of Child and Adolescent Psychiatry at UZH, and Nicole Wenderoth, professor in the Department of Health Sciences and Technology at the ETH Zurich, have succeeded in manipulating the deep sleep of test subjects in targeted areas. "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," says Reto Huber.

Subjective sleep quality was not impaired

In the two-part experiment with six women and seven men, the test subjects had to master three different motoric tasks. The concrete assignment was to learn various sequences of finger movements throughout the day. At night, the brain activity of the test subjects during sleep was monitored by EEG. While the test subjects were able to sleep without disturbance after the learning phase on the first day, their sleep was manipulated in a targeted manner on the second day of the experiment - using acoustic stimulation during the deep sleep phase. To do so, the researchers localized precisely that part of the brain responsible for learning the abovementioned finger movements, i.e., for the control of motor skills (motor cortex). The test subjects were not aware of this manipulation; to them, the sleep quality of both experimental phases was comparable on the following day.

Deep sleep disturbances impair learning efficiency

In a second step, researchers tested how the manipulation of affected the motoric learning tasks on the following day. Here, they observed how the learning and performance curves of the test subjects changed over the course of the experiment. As expected, the participants were particularly able to learn the motoric task well in the morning. As the day went on, however, the rate of mistakes rose. After sleep, the learning efficiency considerably improved again. This was not the case after the night with the manipulated sleep phase. Here, clear performance losses and difficulties in learning the finger movements were revealed. Learning efficiency was similarly as weak as on the evening of the first day of the experiment. Through the manipulation of the motor cortex, the excitability of the corresponding synapses was not reduced during sleep. "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," Nicole Wenderoth explains.

In a controlled experiment with the same task assignment, researchers manipulated another region of the brain during sleep. In this case, however, this manipulation had no effect on the learning of the .

Use in clinical studies planned

The newly gained knowledge is an important step in researching human sleep. The objective of the scientists is to use this knowledge in clinical studies. "Many diseases manifest in sleep as well, such as epilepsy," Reto Huber explains. "Using the new method, we hope to be able to manipulate those specific regions that are directly connected with the disease." This could help improve the condition of affected patients.

Explore further: Finding traces of memory processing during sleep

More information: Sara Fattinger et al, Deep sleep maintains learning efficiency of the human brain, Nature Communications (2017). DOI: 10.1038/ncomms15405

Related Stories

Finding traces of memory processing during sleep

May 17, 2017
Sleep helps us to retain the information that we have learned during the day. We know from animal experiments that new memories are reactivated during sleep. The brain replays previous experience while we sleep – and this ...

Researchers use smartphones and machine learning to measure sleep patterns

April 20, 2017
Despite spending at least one quarter to one third a day sleeping, good sleep can elude many people, and the diagnosis and treatment of sleep disorders remains primitive. Osaka University researchers have designed new technology ...

Analysing the way children sleep could help us to understand autism

March 28, 2017
On average, humans spend roughly a third of their lives asleep. This might sound like quite a long time, but sleep has been shown to be vital for "normal" human functioning. Without enough sleep, things go downhill for most ...

Mice offer a window into sleep's role in memory

March 24, 2017
Sleep provides essential support for learning and memory, but scientists do not fully understand how that process works on a molecular level. What happens to synapses, the connections between neurons, during sleep that helps ...

Developing brain regions in children hardest hit by sleep deprivation

October 4, 2016
A team of researchers from the University of Zurich has studied the effects of acute sleep deprivation in children for the first time. They discovered that the brain in five to 12-year-olds responds differently to sleep deprivation ...

Learning to play the piano? Sleep on it!

August 21, 2014
According to researchers at the University of Montreal, the regions of the brain below the cortex play an important role as we train our bodies' movements and, critically, they interact more effectively after a night of sleep. ...

Recommended for you

New neurons in the adult brain are involved in sensory learning

February 23, 2018
Although we have known for several years that the adult brain can produce new neurons, many questions about the properties conferred by these adult-born neurons were left unanswered. What advantages could they offer that ...

Do you see what I see? Researchers harness brain waves to reconstruct images of what we perceive

February 22, 2018
A new technique developed by neuroscientists at the University of Toronto Scarborough can, for the first time, reconstruct images of what people perceive based on their brain activity gathered by EEG.

Neuroscientists discover a brain signal that indicates whether speech has been understood

February 22, 2018
Neuroscientists from Trinity College Dublin and the University of Rochester have identified a specific brain signal associated with the conversion of speech into understanding. The signal is present when the listener has ...

Study in mice suggests personalized stem cell treatment may offer relief for multiple sclerosis

February 22, 2018
Scientists have shown in mice that skin cells re-programmed into brain stem cells, transplanted into the central nervous system, help reduce inflammation and may be able to help repair damage caused by multiple sclerosis ...

Biomarker, clues to possible therapy found in novel childhood neurogenetic disease

February 22, 2018
Researchers studying a rare genetic disorder that causes severe, progressive neurological problems in childhood have discovered insights into biological mechanisms that drive the disease, along with early clues that an amino ...

A look at the space between mouse brain cells

February 22, 2018
Between the brain's neurons and glial cells is a critical but understudied structure that's been called neuroscience's final frontier: the extracellular space. With a new imaging paradigm, scientists can now see into and ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.