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Patient Robert Linton displays the battery pack implanted in his chest used to power an electrode in his brain during a press conference at Toronto Western Hospital. Deep brain stimulation aims to slow the progression of his Alzheimer's disease. ((Darren Calabrese/Canadian Press))

An experimental brain surgery called deep brain stimulation may slow the progression of early Alzheimer's, scientists in Toronto have found.

The purpose of the experiment on six participants was to implant electrodes in the brain's hippocampus, which plays a role in long-term memory. The electrical conductor acts as a pacemaker-like device in the head just beneath the skin. It is connected to a battery pack in the chest.

Deep brain stimulation has been around for decades. When Dr. Andres Lozano, a neurosurgeon at Toronto's University Health Network, used it in similar experiments on people with Parkinson's disease in 2006, the positive effects didn't last.

An international ethics tribunal decided the electrodes were safe enough to try on people with Alzheimer's disease.

"What we're looking for is a therapy that might delay the illness and improve the quality of life in the patients," said Lozano.

The six patients tested had an average age of 61 and all continued to take Alzheimer's medication.

Of the six, half still experienced mental decline that is typical for the disease. But the other three saw the degenerative effects slow down in standard cognitive function tests known as the mini-mental state exam.

When surgeons tested the electrodes on Robert Linton, 64, he recalled vivid memories of a day spent fishing.

"I'm with my son," Linton recalled to reporters at Toronto Western Hospital. "I could see that muskie coming right at me as I was sitting in the chair, in Technicolor," Linton said as the former city counselor from Brampton, Ont. mimicked the motion of reeling in a fish.

"That's the power of touching a spot in your brain. I'm sold on it."

The research was published in Wednesday's online issue of journal Annals of Neurology.

While it is an "intriguing paper and warrants additional investigations," it remains to be seen whether deep brain stimulation stops progression of the disease or modifies symptoms as Alzheimer's drugs do, said Dr. Ronald Petersen, director of the Mayo Clinic's Alzheimer disease research centre.

Lozano's team is ready to move to a Phase II study. They are recruiting about 50 people to get the stimulator, with half having it activated immediately and the others waiting about six months. None of the participants will know if theirs was activated.

It will be years before the outcome of that study will be known.

The treatment costs between $15,000 and $20,000 per patient, and the batteries last up to five years, Lozano said.

With files from The Canadian Press