Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sleep may help clear the brain for new learning

06.04.2009
A new theory about sleep's benefits for the brain gets a boost from fruit flies in this week's Science. Researchers at Washington University School of Medicine in St. Louis found evidence that sleep, already recognized as a promoter of long-term memories, also helps clear room in the brain for new learning.

The critical question: How many synapses, or junctures where nerve cells communicate with each other, are modified by sleep? Neurologists believe creation of new synapses is one key way the brain encodes memories and learning, but this cannot continue unabated and may be where sleep comes in.

"There are a number of reasons why the brain can't indefinitely add synapses, including the finite spatial constraints of the skull," says senior author Paul Shaw, Ph.D., assistant professor of neurobiology at Washington University School of Medicine in St. Louis. "We were able to track the creation of new synapses in fruit flies during learning experiences, and to show that sleep pushed that number back down."

Scientists don't yet know how the synapses are eliminated. According to theory, only the less important connections are trimmed back, while connections encoding important memories are maintained.

Many aspects of fly sleep are similar to human sleep; for example, flies and humans deprived of sleep one day will try to make up for the loss by sleeping more the next day. Because the human brain is much more complex, Shaw uses the flies as models for answering questions about sleep and memory.

Sleep is a recognized promoter of learning, but three years ago Shaw turned that association around and revealed that learning increases the need for sleep in the fruit fly. In a 2006 paper in Science, he and his colleagues found that two separate scenarios, each of which gave the fruit fly's brain a workout, increased the need for sleep.

The first scenario was inspired by human research linking an enriched environment to improved memory and other brain functions. Scientists found that flies raised in an enhanced social environment—a test tube full of other flies—slept approximately 2-3 hours longer than flies raised in isolation.

Researchers also gave male fruit flies their first exposure to female fruit flies, but with a catch—the females were either already mated or were actually male flies altered to emit female pheromones. Either fly rebuffed the test fly's attempts to mate. The test flies were then kept in isolation for two days and exposed to receptive female flies. Test flies that remembered their prior failures didn't try to mate again; they also slept more. Researchers concluded that these flies had encoded memories of their prior experience, more directly proving the connection between sleep and new memories.

Scientists repeated these tests for the new study, but this time they used flies genetically altered to make it possible to track the development of new synapses, the junctures at which brain cells communicate.

"The biggest surprise was that out of 200,000 fly brain cells, only 16 were required for the formation of new memories, " says first author Jeffrey Donlea, a graduate student. "These sixteen are lateral ventral neurons, which are part of the circadian circuitry that let the fly brain perform certain behaviors at particular times of day."

When flies slept, the number of new synapses formed during social enrichment decreased. When researchers deprived them of their sleep, the decline did not occur.

Donlea identified three genes essential to the links between learning and increased need for sleep: rutabaga, period and blistered. Flies lacking any of those genes did not have increased need for sleep after social enrichment or the mating test.

Blistered is the fruit fly equivalent to a human gene known as serum response factor (SRF). Scientists have previously linked SRF to plasticity, a term for brain change that includes both learning and memory and the general ability of the brain to rewire itself to adapt to injury or changing needs.

The new study shows that SRF could offer an important advantage for scientists hoping to study plasticity: unlike other genes connected to plasticity, it's not also associated with cell survival.

"That's going to be very helpful to our efforts to study plasticity, because it removes a large confounding factor," says co-author Naren Ramanan, Ph.D., assistant professor of neurobiology. "We can alter SRF activity and not have to worry about whether the resulting changes in brain function come from changes in plasticity or from dying cells."

Shaw plans further investigations of the connections between memory and sleep, including the question of how increased synapses induce the need for sleep.

"Right now a lot of people are worried about their jobs and the economy, and some are no doubt losing sleep over these concerns," Shaw says. "But these data suggest the best thing you can do to make sure you stay sharp and increase your chances of keeping your job is to make getting enough sleep a top priority."

Donlea JM, Ramanan N, Shaw PJ. Use-dependent plasticity in clock neurons regulates sleep need in Drosophila.

Science, April 3, 2009.

Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.

Michael C. Purdy | EurekAlert!
Further information:
http://www.wustl.edu

More articles from Studies and Analyses:

nachricht The Great Unknown: Risk-Taking Behavior in Adolescents
19.01.2017 | Max-Planck-Institut für Bildungsforschung

nachricht A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>