(Press-News.org) A study by Johns Hopkins researchers has shown that a widely accepted model of long-term memory formation — that it hinges on a single enzyme in the brain — is flawed. The new study, published in the Jan. 2 issue of Nature, found that mice lacking the enzyme that purportedly builds memory were in fact still able to form long-term memories as well as normal mice could.
"The prevailing theory is that when you learn something, you strengthen connections between your brain cells called synapses," explains Richard Huganir, Ph.D., a professor and director of the Johns Hopkins University School of Medicine's Department of Neuroscience. "The question is, how exactly does this strengthening happen?"
A research group at SUNY Downstate, led by Todd Sacktor, Ph.D., has suggested that key to the process is an enzyme they discovered, known as PKM-zeta. In 2006, Sacktor's group made waves when it created a molecule that seemed to block the action of PKM-zeta — and only PKM-zeta. When the molecule, dubbed ZIP, was given to mice, it erased existing long-term memories. The molecule caught the attention of reporters and bloggers, who mused on the social and ethical implications of memory erasure.
But for researchers, ZIP was exciting primarily as a means for studying PKM-zeta. "Since 2006, many papers have been published on PKM-zeta and ZIP, but no one knew what PKM-zeta was acting on," says Lenora Volk, Ph.D., a member of Huganir's team. "We thought that learning the enzyme's target could tell us a lot about how memories are stored and maintained."
For the current study, Volk and fellow team member Julia Bachman made mice that lacked working PKM-zeta, so-called genetic "knockouts." The goal was to compare the synapses of the modified mice with those of normal mice, and find clues about how the enzyme works.
But, says Volk, "what we got was not at all what we expected. We thought the strengthening capacity of the synapses would be impaired, but it wasn't." The brains of the mice without PKM-zeta were indistinguishable from those of other mice, she says. Additionally, the synapses of the PKM-zeta-less mice responded to the memory-erasing ZIP molecule just as the synapses of normal mice do.
The team then considered whether, in the absence of PKM-zeta, the mouse brains had honed a substitute synapse-building pathway, much in the way that a blind person learns to glean more information from her other senses. So the researchers made mice whose PKM-zeta genes functioned normally until they were given a drug that would suddenly shut the gene down. This allowed them to study PKM-zeta-less adult mice that had had no opportunity to develop a way around the loss of the gene. Still, the synapses of the so-called conditional knockout mice responded to stimuli just as synapses in normal mice did.
What this means, the researchers say, is that PKM-zeta is not the key long-term memory molecule previous studies had suggested, although it may have some role in memory. "We don't know what this ZIP peptide is really acting on," says Volk. "Finding out what its target is will be quite important, because then we can begin to understand at the molecular level how synapses strengthen and how memories form in response to stimuli."
INFORMATION:
Other authors on the paper are Richard Johnson and Yilin Yu, both of the Johns Hopkins University School of Medicine.
This study was supported with funds from the National Institute of Neurological Disorders and Stroke (grant number NS36715), the National Institute of Mental Health (grant number T32MH15330) and the Howard Hughes Medical Institute.
Related stories:
Q&A with Richard Huganir on the Future of Neuroscience and Lifelong Learning: http://www.hopkinsmedicine.org/institute_basic_biomedical_sciences/about_us/scientists/rick_huganir.html
Getting a Grip on Memories: http://www.hopkinsmedicine.org/news/media/releases/getting_a_grip_on_memories
Johns Hopkins Scientists Reveal Molecular Sculptor of Memories: http://www.hopkinsmedicine.org/news/media/releases/johns_hopkins_scientists_reveal_molecular_sculptor_of_memories
Johns Hopkins Researchers Discover How to Erase Memory: http://www.hopkinsmedicine.org/news/media/releases/johns_hopkins_researchers_discover_how_to_erase_memory
HHMI Investigator profile of Richard Huganir: http://www.hhmi.org/research/investigators/huganir_bio.html
END
Astronomers have used the ALMA telescope to get their first glimpse of a fascinating stage of star formation in which planets forming around a young star are helping the star itself continue to grow, resolving a longstanding mystery. The young system, about 450 light-years from Earth, is revealing its complex gravitational dance to the ever-sharpening vision of the Atacama Large Millimeter/submillimeter Array (ALMA), scheduled for completion this year.
As young stars gather material from their surrounding clouds of gas and dust, the incoming material forms a flat, spinning ...
Enormous outflows of charged particles from the centre of our Galaxy, stretching more than halfway across the sky and moving at supersonic speeds, have been detected and mapped with CSIRO's 64-m Parkes radio telescope.
Corresponding to the "Fermi Bubbles" found in 2010, the recent observations of the phenomenon were made by a team of astronomers from Australia, the USA, Italy and The Netherlands, with the findings reported in today's issue of Nature.
"There is an incredible amount of energy in the outflows," said co-author Professor Lister-Staveley-Smith from The University ...
With policymakers and political leaders increasingly unable to combat global climate change, more scientists are considering the use of manual manipulation of the environment to slow warming's damage to the planet.
But a University of Iowa law professor believes the legal ramifications of this kind of geo-engineering need to be thought through in advance and a global governance structure put in place soon to oversee these efforts.
"Geo-engineering is a global concern that will have climate and weather impacts in all countries, and it is virtually inevitable that some ...
Even the best medicines in the world can be rendered ineffective if they are not taken as prescribed. The problem known as medication "non-adherence" is a major health issue in the United States, contributing to worse outcomes for people who have diabetes and other chronic diseases.
Now a study led by researchers at the University of California, San Francisco (UCSF), San Francisco General Hospital and Trauma Center (SFGH) and the Kaiser Permanente Division of Research has identified a significant factor that contributes to poor drug adherence – ineffective communication.
Described ...
January 2, 2013 -- Bisexual men are less likely to disclose and more likely to conceal their sexual orientation than gay men. In the first study to look at the mental health of this population, researchers at Columbia University's Mailman School of Public Health found that greater concealment of homosexual behavior was associated with more symptoms of depression and anxiety.
The study published in the American Psychological Association's Journal of Consulting and Clinical Psychology, examined bisexual men "on the down low," a subgroup of bisexual men who live predominantly ...
In order to study the effectiveness or cost effectiveness of treatments for recurrent cancer, you first have to discover the patients in medical databases who have recurrent cancer. Generally studies do this with billing or treatment codes – certain codes should identify who does and does not have recurrent cancer. A recent study published in the journal Medical Care shows that the commonly used data determinants of recurrent cancer may be misidentifying patients and potentially leading researchers astray.
"For example, a study might look in a database for all patients ...
Following a three-year study using more than 2,800 mice, a University of Missouri researcher was not able to replicate a series of previous studies by another research group investigating the controversial chemical BPA. The MU study is not claiming that BPA is safe, but that the previous series of studies are not reproducible. The MU study, published in the Proceedings of the National Academy of Sciences, also investigated an estrogenic compound found in plants, genistein, in the same three-year study.
"Our findings don't say anything about the positive or negative effects ...
This press release is available in Spanish.
U.S. Department of Agriculture (USDA) scientists are developing strategies to help livestock producers control stable flies, the most damaging arthropod pests of cattle in the United States.
An economic impact assessment by scientists at the Agricultural Research Service (ARS) Agroecosystem Management Research Unit (AMRU) in Lincoln, Neb., looked at four sectors of cattle production: dairy, cow/calf, pastured and range stocker, and animals on feed. They found that stable flies cost the U.S. cattle industry more than $2.4 ...
A new ray of hope has broken through the clouded outcomes associated with Alzheimer's disease. A new research report published in January 2013 print issue of the FASEB Journal by scientists from the National Institutes of Health shows that when a molecule called TFP5 is injected into mice with disease that is the equivalent of human Alzheimer's, symptoms are reversed and memory is restored—without obvious toxic side effects.
"We hope that clinical trial studies in AD patients should yield an extended and a better quality of life as observed in mice upon TFP5 treatment," ...
BOSTON – A small percentage of men in a prostate cancer study complained that their penis seemed shorter following treatment, with some saying that it interfered with intimate relationships and caused them to regret the type of treatment they chose.
Complaints were more common in men treated with radical prostatectomy (surgical removal of the prostate) or male hormone-blocking drugs combined with radiation therapy, according to the study by researchers from Dana-Farber/Brigham and Women's Cancer Center (DF/BWCC). No men reported a perceived shortening of their penis following ...
