People learned better when a key part of their brains got mild zaps of electricity, a finding that may someday help Alzheimer's patients keep more of their memories.

In a small but tantalizing study, participants played a video game in which they learned the locations of stores in a virtual city. They recalled the locations better if they learned them while receiving a painless boost from tiny electrodes buried deep inside their brains.

A brain MRI with an arrow showing where researchers applied deep-brain stimulation during tests on learning. A brain MRI with an arrow showing where researchers applied deep-brain stimulation during tests on learning. (Fried Lab/UCLA/Associated Press)

In the future, that strategy might help curb memory loss for people in the early stages of Alzheimer's disease, suggested Dr. Itzhak Fried, a neurosurgeon at the University of California, Los Angeles. But he cautioned that the results were preliminary.

Using implanted electrodes to treat brain disease is hardly new. Such "deep-brain stimulation" has been used for about a decade for Parkinson's disease and some other disorders. Researchers are also testing it for depression.

Some 80,000 or more people worldwide have had stimulation units implanted, mostly for Parkinson's.

Alzheimer's damage in mice cleared

Mice with early Alzheimer's disease had their symptoms reverse after taking a cancer drug.

The drug Bexarotene is used to treat T-cell lymphoma.

Researchers cautioned against people trying to use it for Alzheimer's because it hasn't been tested in people for that purpose.

Many successful drugs in mice often fail to pan out as safe and effective in humans.

In the study, published in Friday's issue of the journal Science, researchers at Case Western Reserve University in Ohio were investigating ways of reducing levels of beta-amyloid plaque in the brain. The plaques are tied to impaired memory and cognition problems.

More than half of the rodents' plaques had been cleared within 72 hours of being given the drug.

Currently, the best treatment for Alzheimer's disease in mice takes months to reduce plaque in the brain, the researchers said.

"This is a particularly exciting and rewarding study because of the new science we have discovered and the potential promise of a therapy for Alzheimer's disease," said study author Professor Gary Landreth.

"We need to be clear; the drug works quite well in mouse models of the disease. Our next objective is to ascertain if it acts similarly in humans. We are at an early stage in translating this basic science discovery into a treatment."

Fried and colleagues reported the new work in Thursday's issue of the New England Journal of Medicine. It was financed by the federal government and the Dana Foundation.

"I think it's a terrific paper," said Dr. Andres Lozano, a professor of neurosurgery at the University of Toronto, who didn't participate in the work but is studying the approach in Alzheimer's patients. The new work shows stimulation can modify the workings of brain circuits that control memory in people, he said.

But like Fried, he cautioned that the research was still in the early stages.

"Whether it will translate into something useful, we do not know," he said, noting that years of additional study would be needed.

"You don't want to do brain surgery on people unless you have a pretty clear idea you're going to make them better," Lozano said.

Deep-brain electrodes are implanted through holes drilled in the skull.

The study participants were seven epilepsy patients who had the electrodes implanted to help surgeons identify the source of their seizures. Fried and colleagues took advantage of that to stimulate a part of the brain that's key to learning. The patients could not feel the stimulation.

The patients played the video game on a laptop at their beds. Using a joystick, they took the role of taxi drivers in a small town consisting of four blocks by four blocks. They searched for passengers and dropped them off at any of six stores they were asked to find. The electrical stimulation was turned on while they learned the locations of some stores, but not others.

Testing showed that the stimulation made a difference. When given a store to find, the patients took a more direct route to it, and got there faster, if they had learned its location during a time of stimulation. When researchers looked at how much extra wandering they did beyond the shortest possible path, they found that stimulation reduced this excess by an average of 64 per cent.

The patients were tested only a few minutes after learning the store locations, so it's not yet clear how long the effect can last, Fried said. Researchers will also have to see if stimulation helps for other kinds of knowledge, he said.