Passing an electric current through areas deep within the brain could improve memory, research suggests.

A team of Canadian doctors stumbled upon the finding while attempting to treat a morbidly obese man through deep brain stimulation (DBS).

The electrical stimulation caused the patient to experience vivid memories and feelings of déjà vu, which the doctors were not expecting. The findings, reported in the US journal Annals of Neurology, could lead to new treatments for degenerative disorders such as Alzheimer’s disease.

Andres Lozano, of the Toronto Western Hospital, the lead researcher, said: “This is a single case that was totally unexpected. We knew immediately this was important. We are sufficiently intrigued to see if this could help people with memory disorders.”

The team had been trying to help a 50-year-old obese man with type 2 diabetes and sleeping disorders. He had previously failed to respond to diet, medication and psychological help. He had refused gastric surgery and doctors decided that deep brain stimulation, although experimental, was his best option.

The procedure involves electrodes being implanted in the brain under local anaesthesia. They are then stimulated by a “pacemaker” device stitched into the chest that sends electrical pulses to the brain to interfere with neural activity at a particular site.

The technique has been used for more than a decade to treat tremors, and more recently for Parkinson’s disease, chronic pain and depression. Side effects of DBS have included apathy, hallucinations, depression, and even compulsive gambling – although these have mostly been temporary. In tests on animals it has also been found to limit appetite, but it has not been widely tested as a treatment for obesity in people.

In this case the electrodes were implanted in an area of the limbic system called the hypothalamus, which is thought to control appetite. When the electrodes were stimulated by electrical impulses the patient began to experience sudden feelings of déjà vu. He had a perception of being in a park with friends when he was 20 years old. As the intensity of the stimulation increased, details in the scene became more vivid.

Later, when the electrodes were stimulated for a second time, he experienced a similar effect. After three weeks of constant electrical stimulation, the patient also performed better in memory tests.

A year later he again performed well in memory tests when the electrodes were stimulated, but less well when they were switched off. The results suggest that it could be possible to use deep brain stimulation directly to boost memory.

“We hopefully have found a circuit in the brain which can be modulated by stimulation, and which might provide benefit to patients with memory disorders,” Professor Lozano said. He will now lead a pilot study into whether deep brain stimulation can help six patients with early Alzheimer’s disease.

Susanne Sorensen, of the Alzheimer’s Society, said: “As it is difficult to experiment on the living human brain, big leaps in understanding have occasionally been made [when we have had] unexpected results while treating something unrelated or [we have made] observations from rare genetic diseases and unusual lesions.

“The observation made of memories being recovered during this attempt to treat extreme obesity, could be just such a stroke of luck.”

Rebecca Wood, chief executive of the Alzheimer’s Research Trust, welcomed the findings but said that further work was clearly needed. “It will be interesting to see whether this method offers any benefit to people with Alzheimer’s,” she said.

“With the number of people with Alzheimer’s forecast to double within a generation, we urgently need to find ways to tackle this awful disease, but research is hugely underfunded.”

Stimulating memory

1. Patient put under local anaethesia and surgeon carries out a craniotomy – lifting a section of the skull – to access the brain

2. Surgeon implants electrodes deep within the brain into the hypothalamus

3. Electrodes are stimulated by a “pacemaker” device stitched into the chest, which sends electrical pulses to the brain to interfere with neural activity at a particular site, with the effect of triggering memories

Side-effects

How people remember things is still little understood by scientists

Short-term memory Recall from several seconds to a minute later is thought to be supported by transient patterns of communication between brain cells, dependent on regions of the frontal lobe and the parietal lobe

Long-term memory On the other hand, this is maintained by more stable and permanent changes in neural connections widely spread throughout the brain

Hypothalamus The apparent role of the hypothalmus in triggering memory is intriguing, as this complex region was previously associated with controlling body temperature, hunger, thirst, fatigue, anger and sleep patterns

— However, the history of medicine is littered with accidental and chance discoveries. These include penicillin, X-rays and Viagra

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