Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Genetic tags reveal secrets of memories' staying power in mice

25.02.2008
A better understanding of how memory works is emerging from a newfound ability to link a learning experience in a mouse to consequent changes in the inner workings of its neurons. Researchers, supported in part by the National Institutes of Health's National Institute of Mental Health (NIMH), have developed a way to pinpoint the specific cellular components that sustain a specific memory in genetically-engineered mice.

"Remarkably, this research demonstrates a way to untangle precisely which cells and connections are activated by a particular memory," said NIMH Director Thomas Insel, M.D. "We are actually learning the molecular basis of learning and memory."

For a memory to last long-term, the neural connections holding it need to be strengthened by incorporating new proteins triggered by the learning. Yet, it's been a mystery how these new proteins -- born deep inside a neuron -- end up becoming part of the specific connections in far-off neuronal extensions that encode that memory.

By tracing the destinations of such migrating proteins, the researchers located the neural connections, called synapses, holding a specific fear memory. In the process, they discovered these synapses are distinguished by telltale molecular tags that enable them to capture the memory-sustaining proteins.

Mark Mayford, Ph.D., and Naoki Matsuo, Ph.D., of the Scripps Research Institute, report on their findings in the February 22, 2008, issue of the journal Science.

The Scripps researchers have been applying their new technique in a series of studies that focus on progressively finer details of the molecular machinery of memory.

"Inside neurons involved in a specific memory, we're tracing molecules activated by that learning to see how it ultimately changes neural connections," explained Mayford.

In a study published in the August 31, 2007, Science, Mayford and colleagues showed the same neurons activated by a learning experience are also activated when that memory is retrieved. The more neurons involved in the learning, the stronger the memory.

The researchers determined this by genetically engineering a strain of mice with traceable neurons in the brain's fear center, called the amygdala. Inserted genes caused activated neurons to glow red when the animals learned to fear situations where they received shocks, in a process known as fear conditioning -- and to glow green when the memory was later retrieved. The researchers then chemically prevented further expression of those neurons, so that resulting neural and behavioral changes could be confidently attributed to that learning experience at a later time. The study revealed which circuits and neurons were involved in the specific learning experience.

In the new study, Mayford and Matsuo adapted this approach to discover how fear learning works at a deeper level -- inside neurons of the brain's memory hub, called the hippocampus.

Evidence suggested that proteins called AMPA receptors strengthen memories by becoming part of the synapses encoding them. To identify these synapses, the researchers genetically engineered a strain of mice to express AMPA receptors traceable by a green glow. After fear conditioning had triggered new AMPA receptors deep in the neuron's nucleus, they chemically suppressed any further expression of the proteins. This allowed time for the receptors to migrate to their appointed synapses. Hours later, green fluorescence revealed the fate of the specific AMPA receptors born in response to the learning.

As expected, the newly synthesized AMPA receptors had traveled and become part of only certain hippocampus synapses -- presumably the ones holding the memory. Synaptic connections are made onto small nubs on the neuron called spines. These spines come in three different shapes called thin, stubby and mushroom. While little was known about the function of these differently shaped spines, the fact that they are altered in various forms of mental retardation, like Fragile-X syndrome, suggests a critical importance in mental function.

The researchers discovered the synapses that received the AMPA receptors with memory were limited to the mushroom type. The mushroom spines also figured prominently in the same neurons when the fear conditioning was reversed by repeatedly exposing the animals to the feared situation without getting shocked -- a procedure called extinction learning. This indicated that the same neurons activated when a fear is learned are also activated when it is lost. The surge in mushroom spine capture of the receptors appeared within hours of learning and was gone after a few days, but appeared to be critical for cementing the memory.

Jules Asher | EurekAlert!
Further information:
http://www.nih.gov
http://www.nimh.nih.gov

Further reports about: AMPA Mayford Neuron Receptors connections mushroom neural spine synapses

More articles from Life Sciences:

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Periodic ventilation keeps more pollen out than tilted-open windows

29.03.2017 | Health and Medicine

Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems

29.03.2017 | Earth Sciences

OLED production facility from a single source

29.03.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>