Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Memory Relies on Astrocytes, the Brain's Lesser Known Cells

30.07.2014

Salk scientists show that the little-known supportive cells are vital in cognitive function.

When you’re expecting something—like the meal you’ve ordered at a restaurant—or when something captures your interest, unique electrical rhythms sweep through your brain.


Salk Institute for Biological Studies

Salk scientists discover link between astrocytes and memory.

These waves are called gamma oscillations and they reflect a symphony of cells—both excitatory and inhibitory—playing together in an orchestrated way. Though their role has been debated, gamma waves have been associated with higher-level brain function, and disturbances in the patterns have been tied to schizophrenia, Alzheimer’s disease, autism, epilepsy and other disorders.

Now, new research from the Salk Institute shows that little known supportive cells in the brain known as astrocytes may in fact be major players that control these waves.

In a study published July 28 in the Proceedings of the National Academy of Sciences, Salk researchers report a new, unexpected strategy to turn down gamma oscillations by disabling not neurons but astrocytes. In the process, the team showed that astrocytes, and the gamma oscillations they help shape, are critical for some forms of memory.

“This is what could be called a smoking gun,” says co-author Terrence Sejnowski, head of the Computational Neurobiology Laboratory at the Salk Institute for Biological Sciences and a Howard Hughes Medical Institute investigator. “There are hundreds of papers linking gamma oscillations with attention and memory, but they are all correlational. This is the first time we have been able to do a causal experiment, where we selectively block gamma oscillations and show that it has a highly specific impact on how the brain interacts with the world.”

A collaboration among the labs of Salk professors Sejnowski, Inder Verma and Stephen Heinemann found that activity in the form of calcium signaling in astrocytes immediately preceded gamma oscillations in the brains of mice. This suggested that astrocytes, which use many of the same chemical signals as neurons, could be influencing these oscillations.

To test their theory, the group used a virus carrying tetanus toxin to disable the release of chemicals released selectively from astrocytes, effectively eliminating the cells’ ability to communicate with neighboring cells. Neurons were unaffected by the toxin.

After adding a chemical to trigger gamma waves in the animals’ brains, the researchers found that brain tissue with disabled astrocytes produced shorter gamma waves than in tissue containing healthy cells. And, after adding three genes that would allow the researchers to selectively turn on and off the tetanus toxin in astrocytes at will, they found that gamma waves were dampened in mice whose astrocytes were blocked from signaling. Turning off the toxin reversed this effect.

The mice with the modified astrocytes seemed perfectly healthy. But after several cognitive tests, the researchers found that they failed in one major area: novel object recognition. As expected, healthy mouse spent more time with a new item placed in its environment than it did with familiar items. In contrast, the group’s new mutant mouse treated all objects the same.

“That turned out to be a spectacular result in the sense that novel object recognition memory was not just impaired, it was gone—as if we were deleting this one form of memory, leaving others intact,” Sejnowski says.

The results were surprising, in part because astrocytes operate on a seconds- or longer timescale whereas neurons signal far faster, on the millisecond scale. Because of that slower speed, no one suspected astrocytes were involved in the high-speed brain activity needed to make quick decisions.

“What I thought quite unique was the idea that astrocytes, traditionally considered only guardians and supporters of neurons and other cells, are also involved in the processing of information and in other cognitive behavior,” says Verma, a professor in the Laboratory of Genetics and American Cancer Society Professor.

It’s not that astrocytes are quick—they’re still slower than neurons. But the new evidence suggests that astrocytes are actively supplying the right environment for gamma waves to occur, which in turn makes the brain more likely to learn and change the strength of its neuronal connections.

Sejnowski says that the behavioral result is just the tip of the iceberg. “The recognition system is hugely important,” he says, adding that it includes recognizing other people, places, facts and things that happened in the past. With this new discovery, scientists can begin to better understand the role of gamma waves in recognition memory, he adds.

Collaborators included Hosuk Sean Lee of the Department of Life Sciences in Sogang University in Seoul, South Korea; Andrea Ghetti, Gustavo Dziewczapolski and Juan C. Piña-Crespo of the Molecular Neurobiology Laboratory at Salk; António Pinto-Duarte of the Institute of Pharmacology and Neurosciences, Faculty of Medicine and the Institute of Molecular Medicine Neurosciences Unit at the University of Lisbon in Portugal; Xin Wang of Salk’s Computational Neurobiology Laboratory; Francesco Galimi of Salk and the Department of Biomedical Sciences/Istituto Nazionale di Biostrutture e Biosistemi, University of Sassari Medical School in Sassari, Italy; and Salvador Huitron-Resendiz and Amanda J. Roberts of the Mouse Behavioral Assessment Core at the Scripps Research Institute, in La Jolla, California.

The work was supported by a Salk Innovation Grant, Kavli Innovative Research Awards, a Calouste Gulbenkian Foundation Fellowship, a Life Sciences Research Foundation Pfizer Fellowship, the Brain and Behavior Research Foundation, the Bundy Foundation, Jose Carreras International Leukemia Foundation, the Pew Charitable Trusts, National Science Foundation, Howard Hughes Medical Institute, the Office of Naval Research, and the National Institutes of Health.

About the Salk Institute for Biological Studies:
The Salk Institute for Biological Studies is one of the world's preeminent basic research institutions, where internationally renowned faculty probe fundamental life science questions in a unique, collaborative and creative environment. Focused both on discovery and on mentoring future generations of researchers, Salk scientists make groundbreaking contributions to our understanding of cancer, aging, Alzheimer's, diabetes and infectious diseases by studying neuroscience, genetics, cell and plant biology, and related disciplines.

Faculty achievements have been recognized with numerous honors, including Nobel Prizes and memberships in the National Academy of Sciences. Founded in 1960 by polio vaccine pioneer Jonas Salk, MD, the Institute is an independent nonprofit organization and architectural landmark.

Kristina Grifantini | newswise

Further reports about: Cells Medicine Neurobiology astrocytes neurons oscillations waves

More articles from Life Sciences:

nachricht Biology in a twist -- deciphering the origins of cell behavior
31.03.2015 | National University of Singapore

nachricht Speech dynamics are coded in the left motor cortex
31.03.2015 | Universitätsmedizin Göttingen - Georg-August-Universität

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Experiment Provides the Best Look Yet at 'Warm Dense Matter' at Cores of Giant Planets

In an experiment at the Department of Energy's SLAC National Accelerator Laboratory, scientists precisely measured the temperature and structure of aluminum as...

Im Focus: Energy-autonomous and wireless monitoring protects marine gearboxes

The IPH presents a solution at HANNOVER MESSE 2015 to make ship traffic more reliable while decreasing the maintenance costs at the same time. In cooperation with project partners, the research institute from Hannover, Germany, has developed a sensor system which continuously monitors the condition of the marine gearbox, thus preventing breakdowns. Special feature: the monitoring system works wirelessly and energy-autonomously. The required electrical power is generated where it is needed – directly at the sensor.

As well as cars need to be certified regularly (in Germany by the TÜV – Technical Inspection Association), ships need to be inspected – if the powertrain stops...

Im Focus: 3-D satellite, GPS earthquake maps isolate impacts in real time

Method produced by UI researcher could improve reaction time to deadly, expensive quakes

When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure--and lives--can be saved.

Im Focus: Atlantic Ocean overturning found to slow down already today

The Atlantic overturning is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. Also known as the Gulf Stream system, it is responsible for the mild climate in northwestern Europe. 

Scientists now found evidence for a slowdown of the overturning – multiple lines of observation suggest that in recent decades, the current system has been...

Im Focus: Robot inspects concrete garage floors and bridge roadways for damage

Because they are regularly subjected to heavy vehicle traffic, emissions, moisture and salt, above- and underground parking garages, as well as bridges, frequently experience large areas of corrosion. Most inspection systems to date have only been capable of inspecting smaller surface areas.

From April 13 to April 17 at the Hannover Messe (hall 2, exhibit booth C16), engineers from the Fraunhofer Institute for Nondestructive Testing IZFP will be...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference On Regenerative Medicine 2015: Registration And Abstract Submission Now Open

25.03.2015 | Event News

University presidents from all over the world meet in Hamburg

19.03.2015 | Event News

10. CeBiTec Symposium zum Big Data-Problem

17.03.2015 | Event News

 
Latest News

Biology in a twist -- deciphering the origins of cell behavior

31.03.2015 | Life Sciences

Wrapping carbon nanotubes in polymers enhances their performance

31.03.2015 | Materials Sciences

Research Links Two Millennia of Cyclones, Floods, El Niño

31.03.2015 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>