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Canadian researchers have stumbled upon what may be a promising key to improving memory in patients by stimulating electrodes in the brain, a major discovery that could lead to a breakthrough in the treatment of Alzheimer's disease and other memory disorders.

Using a procedure known as deep brain stimulation, in which electrodes are implanted in the brain, researchers have found they can activate a patient's memory circuits, provoke images and enhance memory performance over a long period of time.

While DBS is already used to help patients with Parkinson's disease and other movement disorders, this is believed to be the first time the procedure has been found to have an effect on memory.

The findings, published today in the American Neurological Association's Annals of Neurology journal, could represent a landmark development in therapies to help people with memory disorders.

"What we're hoping to do is to provide some symptomatic relief, changes in memory function, that in the long run may actually preserve independence and quality of life for a longer period," said Mary Pat McAndrews, a neuropsychologist at Toronto Western Hospital and one of the study's investigators.

An increasing number of researchers around the world are exploring whether DBS can be used to treat a growing range of psychiatric problems and brain disorders, including depression and obsessive-compulsive disorder.

In the new study, a team of researchers at Toronto Western Hospital discovered the link between DBS and memory improvement by chance.

They had been conducting an experimental study to determine whether they could treat a 50-year-old morbidly obese man by stimulating appetite suppressant sites in the hypothalamus, the part of the brain responsible for hunger, thirst and other bodily functions.

But when researchers turned on the electrode stimulator, the patient, who was awake during surgery, immediately said he recalled a past vision of being in the park with friends when he was about 20 years old. When the stimulator's intensity was increased, his visions became more vivid and detailed.

"We knew that was somewhat of a eureka moment because we knew that this was something quite unusual," said Andres Lozano, the study's principal investigator and Canada Research Chair in neuroscience.

Excited by the findings, Dr. Lozano and his team shifted their focus to the man's memory circuits and discovered they could reproduce the effects in a more rigorous study setting.

"We have now direct evidence that by stimulating in this area, we are driving activity in the memory circuit," said Dr. Lozano, who is also a neurosurgery professor at the University of Toronto.

Researchers also believe the procedure has a long-lasting effect on memory based on psychological tests that were conducted before and after DBS surgery. While most aspects of the patient's tests remained the same after surgery, he demonstrated a substantial boost in his memory scores.

"Selectively, only his memory functions seem to have improved and they've improved quite significantly," Dr. Lozano said.

The discovery represents a major breakthrough for scientists, who have an extremely limited understanding of which parts of the brain are responsible for memory in humans.

This finding demonstrates that it's possible to access and influence memory circuits to improve their function, which may lead to the development of new treatments and therapy for tens of thousands of people with Alzheimer's disease and other memory problems, Dr. Lozano said.

"Specifically, it may be possible to access these circuits in patients who have memory deficits and to try to enhance them and bring them to a more normal level of function," he said.

In order to do this, Dr. Lozano and the team at Toronto Western Hospital have launched a new study involving a group of Alzheimer's patients to determine whether this type of DBS surgery is safe and can improve memory function.

"If this is reliable, which means we can replicate it and show it again and again, it could be quite profound," Dr. McAndrews said.

So far, researchers have performed the surgery on three out of six patients with early Alzheimer's disease and while they can't yet discuss the data, Dr. Lozano said the results look "promising."

If the study is successful, Dr. Lozano said they can begin considering larger trials to determine whether DBS surgery is a realistic treatment option for Alzheimer's patients.

He said it's possible that eventually DBS surgery for people with memory disorders could become as widespread as it has for the treatment of Parkinson's disease.

Patients who undergo DBS surgery have electrodes implanted in their brains that can be connected through wires under the skin to a replaceable battery unit implanted beneath the collarbone that delivers electrical signals to the brain.