Navigation Links
Genetic tags reveal secrets of memories' staying power in mice
Date:2/21/2008

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.


'/>"/>

Contact: Jules Asher
NIMHpress@nih.gov
301-443-4536
NIH/National Institute of Mental Health
Source:Eurekalert  

Related biology news :

1. U-M researchers release most detailed global study of genetic variation
2. Total, genetically-based recall
3. Genetic corridors are next step to saving tigers
4. Researchers decode genetics of rare photosynthetic bacterium
5. Researchers decode genetics of rare photosynthetic bacteria
6. Europes most common genetic disease is a liver disorder
7. Is political orientation transmitted genetically?
8. Ecological genetics of freshwater bacteria surveyed
9. Environmental epigenetics has potential for preventing and treating disease
10. Scientists achieve major genetics breakthrough
11. Genetic material under a magnifying glass
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Genetic tags reveal secrets of memories' staying power in mice
(Date:3/31/2016)... , March 31, 2016 ... ) ("LegacyXChange" or the "Company") LegacyXChange is ... users of its soon to be launched online site ... https://www.youtube.com/channel/UCyTLBzmZogV1y2D6bDkBX5g ) will also provide potential shareholders ... of DNA technology to an industry that is notorious ...
(Date:3/29/2016)... , March 29, 2016 LegacyXChange, ... LegacyXChange "LEGX" and SelectaDNA/CSI Protect are pleased to announce ... used in a variety of writing instruments, ensuring athletes ... originally created collectibles from athletes on LegacyXChange will be ... of the DNA. Bill Bollander , ...
(Date:3/22/2016)... , March 22, 2016 ... report "Electronic Sensors Market for Consumer Industry by Type ... Others), Application (Communication & IT, Entertainment, Home ... Global Forecast to 2022", published by MarketsandMarkets, ... expected to reach USD 26.76 Billion by ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... ... June 23, 2016 , ... ClinCapture, ... Pennsylvania Convention Center and will showcase its product’s latest features from June 26 ... presenting a scientific poster on Disrupting Clinical Trials in The Cloud during the ...
(Date:6/23/2016)... ... June 23, 2016 , ... ... of intelligent tools designed, tuned and optimized exclusively for Okuma CNC machining centers ... The result of a collaboration among several companies with expertise in toolholding, cutting ...
(Date:6/23/2016)... India , June 23, 2016 ... media market research report to its pharmaceuticals section ... profiles, product details and much more. ... spread across 151 pages, profiling 15 companies and ... available at http://www.reportsnreports.com/reports/601420-global-cell-culture-media-industry-2016-market-research-report.html . ...
(Date:6/22/2016)... Research and Markets has announced the addition of the "Biomarkers: ... The global biomarkers market has grown ... market is expected to grow at a five-year compound annual growth ... billion in 2015 to $96.6 billion in 2020. ... 2020) are discussed. As well, new products approved in 2013 and ...
Breaking Biology Technology: