最新医学新闻 | Study Sheds Light on Molecular Encoding of Memory

Written by Catharine Paddock PhD

Published: Fri 18 December 2015 at 3am PST

Abstract

A new study supports the idea that chemical tagging of DNA - a process known as DNA methylation - may be how memories are encoded in the brain.

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The study, by researchers from the German Center for Neurodegenerative Diseases (DZNE) in Göttingen and Munich, is published in Nature Neuroscience.

There is still a lot we do not know about how the brain deals with memory and learning - the ability to draw conclusions from memories.

A widely held theory is that memories are encoded by changing the connections between brain cells. This is the idea behind brain “plasticity” - the way the brain changes through life.

The study shows that epigenetic changes involved in memory formation also occur in non-neuronal cells.

The forming, strengthening and weakening of the connections in the brain is controlled by changes in gene expression, a process that occurs at the molecular level by adding and removing chemical tags.

This process of altering the expression of genes in DNA - such as turning them on and off - without altering the DNA itself is called “epigenetics.”

The epigenetic changes are made to the backbone of the DNA - by adding or removing chemical markers or tags at specific sites - this is called DNA methylation.

Changes in histones - the proteins that package the DNA into cell nuclei - can also occur.

DNA methylation helps control brain plasticity

Thus, the epigenetic theory of memory suggests that if you had two brains with identical DNA and exposed them to different experiences, their DNA would still be the same afterward, but they would carry different epigenetic markers.

Coauthor Dr. Magali Hennion, a researcher in computational systems biology, says:

“Research on epigenetic changes that are related to memory processes is still at an early stage.”

To see what happens at the molecular level when long-term memory is encoded, the researchers trained mice to recognize a specific test environment and then looked for epigenetic changes in the DNA of their brain cells.

They found evidence of both types of epigenetic changes - DNA methylation, or chemical markers on the DNA backbone - and histone alterations.

However, they also found other details that could be important for future research into memory and diseases associated with memory and learning.

One discovery is that histone modification appears to have little effect on the genes involved in brain plasticity.

The other discovery is that the epigenetic changes involved in memory formation occur not only in neurons, the primary signaling cells, but also in non-neuronal cells - the glial cells that support neurons and vastly outnumber them.

The researchers plan to look more closely at the involvement of non-neuronal cells in memory. Meanwhile, they conclude that their study provides evidence that DNA methylation helps control brain plasticity and may be an important molecular process for long-term memory.

They suggest methylation could be a potential treatment target for conditions such as Alzheimer’s disease that impair memory. The team intends to focus on this aspect in future research, as Dr. Hennion explains:

“We look at such features, not only for the purpose of a better understanding of how memory works. We also look for potential targets for drugs that may counteract memory decline. Ultimately, our research is about therapies against Alzheimer’s and similar brain diseases.”

Meanwhile, Medical News Today recently learned how playing 3D video games may help boost memory. New research from the University of California-Irvine shows playing such games can improve memory performance by around 12%, suggesting it could be a way to preserve memory function as we age.