The technique here is known as deep brain stimulation -- applying electricity directly to regions of the brain. It has been used in tens of thousands of patients with Parkinson's as well as having an emerging role in Tourette's Syndrome and depression.

　　The study at the University of Toronto took six patients with the condition. Deep brain stimulation was applied to the fornix -- a part of the brain which passes messages onto the hippocampus.

　　Lead researcher Prof Andres Lozano said you would expect the hippocampus to shrink by five per cent on average in a year in patients with Alzheimer's.

　　After 12 months of stimulation, he said one patient had a five per cent increase and another had an eight per cent increase.

　　Prof Lozano told BBC: "This is the first time that brain stimulation in a human being has been shown to grow an area of your brain."

　　"It was an amazing finding for us," he said.

　　The findings were presented at the Society for Neuroscience conference in November but they have yet to be published in an academic journal.

　　To test whether this is really working, rather than being a fluke result, the researchers are going to perform a larger trial.