Researchers find a brain enzyme that plays integral role in the maintenance of long-term memory

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Super molecule enhances, erases memory

Researchers find a brain enzyme that plays integral role in the maintenance of

long-term memory

By Welsh, LiveScience Staff Writer

Taking the memory-erasing ability shown in the 2004 movie " Eternal Sunshine of

the Spotless Mind " a step further, scientists have found a molecule that not

only erases but also augments and strengthens memories, months after the fact.

" If you take coffee or amphetamines that make the brain more excitable, your

initial learning can be a little better, as any student would know, " said

researcher Todd Sacktor of SUNY Downstate Medical Center. " What never had been

done before was to be able to, after you learn something, wait days to weeks

later, and then do something that would be able to enhance those previously

stored memories. "

Previous studies of memory-modulating compounds have mainly been focused on

treatment during periods of learning or remembering. Sacktor's research has

pinpointed a brain enzyme that plays an integral role in the maintenance of

long-term memory.

Where memories are made

Sacktor and co-researcher Yadin Dudai of the Weizmann Institute of Science in

Israel conditioned rats to associate a taste with feeling sick to their

stomachs, much like humans after a particularly nasty batch of food poisoning.

This memory becomes encoded in the brain and for months after the nauseating

experience the rats avoid any similar-tasting foods.

To change the rats' memories the researchers first trained them to associate

certain foods with bellyaches, then injected them with a non-illness-inducing

virus made specifically to express a memory-altering enzyme. The enzyme is

called protein kinase M zeta, or PKMzeta for short. The virus made either the

working version of the protein or a mutant form that blocked the activity of

even the naturally expressed protein.

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They saw that the increased enzyme levels enhanced the rat's ability to

remember, while the activity-blocking mutant wiped out the memory.

PKMzeta appears to work in a different way than other memory enhancers, which

seem to boost our brain's natural means of consolidating, or turning everyday

experiences into lasting memories. But scientists didn't know the mechanism that

keeps these long-term memories accessible after consolidation.

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Dudai and his team believe that PKMzeta is integral in this " sustainability " of

memories. " People used to think that memory maintenance is a passive process,

that there wasn't much to put into it, that you just change the wiring, " Karim

Nader, a researcher at McGill University in Canada who wasn't involved in the

study, said. " This suggests that the mechanisms of memory maintenance are

actively maintained, and even manipulated. "

Next memory-boosting drug?

In the future, it's possible this protein could be the target of memory-changing

drugs. Such drugs could treat Alzheimer's patients, by strengthening their

memories, or individuals with post-traumatic stress disorder (PTSD) as well as

phobia patients, by decreasing their memory of fear-inducing moments. Different

memories could be targeted by changing PKMzeta in different brain areas.

" There are other molecules that have been implicated in memory maintenance, "

Glanzman of UCLA, who wasn't involved in the study, told LiveScience. " But

it's clear that PKMzeta is a sort of master molecule. "

Even after having their memory of the nauseating taste wiped out, the rats could

still relearn to dislike it, similar to (spoiler alert!) the reunion of the

“Spotless Mind†characters after their first memory wipe. " That area of the

brain is still capable of learning new things, " Dudai said. " We didn't damage it

to such a degree that we interfered with this ability. "

This study will be published in the March 4 issue of the journal Science.