Brain researchers discover key gene necessary for capturing memories

October 07, 1994|By Newsday

COLD SPRING HARBOR, N.Y. -- Two teams of scientists working to sort out how the brain works have found a specific gene needed for making memories. Without it, animals end up handicapped, unable to remember what happened just a short time ago.

In three research papers to be published in today's issue of the scientific journal Cell, researchers at the Cold Spring Harbor Laboratory on Long Island report that the gene called CREB must be working properly or memories won't last. The gene plays the same role -- consolidating long-term memory -- in creatures as varied as mice and fruit flies, and probably in humans, too.

"We are trying to uncover the physiological bases of learning and memory," said neuroscientist Alcino Silva. And "clearly, we'd like to look at the impact of this new information in human memory studies."

Behavioral geneticist Tim Tully said work in his laboratory with fruit flies has also shown that there are two distinct genetic systems that work separately to make memories permanent. In other words, permanent memories can be established through two parallel systems.

Dr. Silva noted that "learning and memory are so central to an organism's function that there are many safeguards" built into the brain. "There is never a complete loss of memory. In the CREB mutants, it's not complete; with intensive training they do learn something. There's no such thing as an all-or-none phenomenon."

Both teams involved in the three papers focused on the CREB gene, which is thought to serve as one link among many in a chain of molecular events that leads from an experience -- when something must be learned -- to the "consolidation" of a memory among brain cells. It is the consolidation step that seems to be blocked when the CREB gene is damaged. Without CREB, a temporary memory cannot become permanent.

"The mutant mice are profoundly deficient in long-term memory," Dr. Silva said. But, "strikingly, short-term memory -- lasting between 30 and 60 minutes -- appears to be intact" in the `D animals.

It has long been known that long-term memory can be blocked by drugs, electric shocks or other treatments soon after an animal has had a training experience.

But the exact chemistry and biology involved have been elusive.

It is known, however, that certain genes must be activated to make proteins, if a memory is to become permanent.

The CREB gene seems to be one of them.

Dr. Tully also noted that disruption of another gene, called radish, can erase the other form of long-term memory. Scientists working with fruit flies have a tradition of giving their mutant flies whimsical names, such as rutabaga, radish, stuck and shot-full-of-holes.

The experiments by the Tully and Silva teams fit the idea that long-term memory is a phenomenon that depends on structural changes being made in nerve cells. These changes appear to solidify or strengthen the connections between nerve cells, making the passage of signals easier.

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