Researchers unravel mystery behind long-lasting memories

August 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)

Related Stories

Recommended for you

Brain activity buffers against worsening anxiety

November 17, 2017
Boosting activity in brain areas related to thinking and problem-solving may also buffer against worsening anxiety, suggests a new study by Duke University researchers.

Investigating patterns of degeneration in Alzheimer's disease

November 17, 2017
Alzheimer's disease (AD) is known to cause memory loss and cognitive decline, but other functions of the brain can remain intact. The reasons cells in some brain regions degenerate while others are protected is largely unknown. ...

Neuroscience research provides evidence the brain is strobing, not constant

November 17, 2017
It's not just our eyes that play tricks on us, but our ears. That's the finding of a landmark Australian-Italian collaboration that provides new evidence that oscillations, or 'strobes', are a general feature of human perception.

Study may point to new treatment approach for ASD

November 17, 2017
Using sophisticated genome mining and gene manipulation techniques, researchers at Vanderbilt University Medical Center (VUMC) have solved a mystery that could lead to a new treatment approach for autism spectrum disorder ...

Neuroscientists find chronic stress skews decisions toward higher-risk options

November 16, 2017
Making decisions is not always easy, especially when choosing between two options that have both positive and negative elements, such as deciding between a job with a high salary but long hours, and a lower-paying job that ...

Paraplegic rats walk and regain feeling after stem cell treatment

November 16, 2017
Engineered tissue containing human stem cells has allowed paraplegic rats to walk independently and regain sensory perception. The implanted rats also show some degree of healing in their spinal cords. The research, published ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.