Researchers unravel mystery behind long-lasting memories

Aug 11, 2009

A new study by researchers at Wake Forest University School of Medicine may reveal how long-lasting memories form in the brain.

The researchers hope that the findings, now available online and scheduled to appear in an upcoming issue of Neuroscience, may one day help scientists develop treatments to prevent and treat conditions such as post-traumatic stress disorder.

"Although many things are known about memories that form from repeat experiences, not much is known with regard to how some memories form with just one exposure," said Ashok Hegde, Ph.D., an associate professor of neurobiology and anatomy and the lead investigator on the study.

Scientists do know that people tend to remember extremely happy or sad occasions vividly because of the emotional connection, Hegde said. Extreme emotions trigger the release of a chemical in the brain called norepinephrine, which is related to adrenaline. That norepinephrine somehow helps memories last a long time - some even a lifetime.

For example, he said, when a person asks, "Where were you when the 9/11 attacks happened?" most people can recall immediately where they were and what they were doing when they heard the news. They remember the moment as if it just happened because a national tragedy arouses emotion and emotion somehow makes memories last for a long time, Hegde explained.

For the current study, Hegde and colleagues looked at how norepinephrine helps female mice remember the scent of their male partners after being exposed to it just once during mating.

The researchers studied the in the accessory olfactory bulb, the part of the brain where of the male partner's scent is stored. They found that norepinephrine, released in mice while mating, activates an enzyme called Protein Kinase C (PKC), specifically, the "alpha" of PKC, in the accessory olfactory bulb. The PKC enzyme has about a dozen forms, or isoforms, that exist in the brains of mammals, including humans.

"The fact that PKC-alpha is activated through the release of norepinephrine is an important discovery," Hegde said. "It explains how strong memories form for specific sensory experiences."

In female mice, the information about the partner's scent is carried by a chemical called glutamate and the fact that mating has occurred is conveyed by the release of norepinephrine, Hegde explained. Previous studies have found that glutamate and norepinephrine together, but not individually, cause strong memory formation for the male's scent.

"No one knew how this happened," Hegde said. "Our findings indicate that the PKC-alpha enzyme tells the nerve cells in the brain that these two chemicals have arrived together. PKC-alpha is like the bouncer who lifts the rope blocking the entrance to an exclusive club for strong memories when glutamate and norepinephrine arrive together. If they arrive alone, they can't get past the velvet rope."

Hegde explained that, when memory is stored in the brain, the connections between nerve cells, called synapses, change. Strong memories are formed when synapses become stronger through structural changes that occur at the synapse. PKC-alpha works with glutamate and to create those changes.

Hegde said that the next step in this line of research is to learn exactly how PKC-alpha can turn genes on in . Understanding the precise sequence of molecules that are activated by PKC-alpha will help researchers block the function of these molecules and test whether they block memory formation. This future research will not only explain strong pleasant memories, but also how strong unpleasant memories form in instances like .


Join PhysOrg.com on Facebook!
Follow PhysOrg.com on Twitter!

Source: Wake Forest University Baptist Medical Center (news : web)

Explore further: When bad news are good news for neurodegenerative diseases

add to favorites email to friend print save as pdf

Related Stories

Researchers make new finding about how memory is stored

Apr 23, 2008

Researchers at Wake Forest University School of Medicine are the first to show that the location of protein-destroying “machines” in nerve cells in the brain may play an important role in how memories are formed – a ...

Recommended for you

Know the brain, and its axons, by the clothes they wear

Apr 18, 2014

(Medical Xpress)—It is widely know that the grey matter of the brain is grey because it is dense with cell bodies and capillaries. The white matter is almost entirely composed of lipid-based myelin, but ...

Turning off depression in the brain

Apr 17, 2014

Scientists have traced vulnerability to depression-like behaviors in mice to out-of-balance electrical activity inside neurons of the brain's reward circuit and experimentally reversed it – but there's ...

Rapid whole-brain imaging with single cell resolution

Apr 17, 2014

A major challenge of systems biology is understanding how phenomena at the cellular scale correlate with activity at the organism level. A concerted effort has been made especially in the brain, as scientists are aiming to ...

User comments : 0

More news stories

Scientists make critical end-stage liver discovery

(Medical Xpress)—A team of researchers in the University of Arizona's College of Pharmacy has discovered a molecular pathway that could be key to creating new therapeutics that would slow or even reverse ...

Atom probe assisted dating of oldest piece of earth

(Phys.org) —It's a scientific axiom: big claims require extra-solid evidence. So there were skeptics in 2001 when University of Wisconsin-Madison geoscience professor John Valley dated an ancient crystal ...