Scientists performing experimental brain surgery on a man aged 50 have stumbled across a mechanism that could unlock how memory works.
The accidental breakthrough came during an experiment originally intended to suppress the obese man’s appetite, using the increasingly successful technique of deep-brain stimulation. Electrodes were pushed into the man’s brain and stimulated with an electric current. Instead of losing appetite, the patient instead had an intense experience of déjà vu. He recalled, in intricate detail, a scene from 30 years earlier. More tests showed his ability to learn was dramatically improved when the current was switched on and his brain stimulated.
Scientists are now applying the technique in the first trial of the treatment in patients with Alzheimer’s disease. If successful, it could offer hope to sufferers from the degenerative condition, which affects 450,000 people in Britain alone, by providing a “pacemaker” for the brain.
Three patients have been treated and initial results are promising, according to Andres Lozano, a professor of neurosurgery at the Toronto Western Hospital, Ontario, who is leading the research.
Professor Lozano said: “This is the first time that anyone has had electrodes implanted in the brain which have been shown to improve memory. We are driving the activity of the brain by increasing its sensitivity – turning up the volume of the memory circuits. Any event that involves the memory circuits is more likely to be stored and retained.”
The discovery had caught him and his team “completely by surprise”, Professor Lozano said. They had been operating on the man, who weighed 190kg (30st), to treat his obesity by locating the point in his brain that controls appetite. All other attempts to curb his eating had failed and brain surgery was the last resort.
The treatment for obesity was unsuccessful. But, while the researchers were identifying potential appetite suppressant points in the hypothalamus, the part of the brain associated with hunger, the man suddenly began to say that memory was flooding back.
“He reported the experience of being in a park with friends from when he was around 20 years old and, as the intensity of stimulation increased, the details became more vivid. He recognised his girlfriend [from the time] … The scene was in colour. People were wearing identifiable clothes and were talking, but he could not decipher what they were saying,” the researchers write in Annals of Neurology, published today.
The man, who has not been identified, was also tested on his ability to learn lists of paired objects. After three weeks of continuous hypothalamic stimulation, his performance on two learning tests was significantly improved. He was also much more likely to remember a list of unrelated paired objects with the electrodes turned on than when turned off.