February 18, 2008

A Stimulating Experience

Once used to treat Parkinson's and other movement disorders, deep brain stimulation surgery, or DBS, may have the potential to treat a wide variety of other conditions.

For example, DBS of the part of the brain called the hypothalamus has been used to treat cluster headaches and aggression in humans, and studies have shown that stimulating this area affects feeding behavior in animals. Now, a new study has found that hypothalamic DBS performed on a person with morbid obesity unexpectedly triggered long-buried memories.

DBS involves using a surgically implanted, battery-operated medical device called a neurostimulator, which is about the size of a stopwatch, to deliver electrical stimulation to targeted areas in the brain.

Led by Andres Lozano, Professor of Neurosurgery and Canada Research Chair in Neuroscience and his team at the Toronto Western Hospital in Toronto, Ontario, researchers conducted an experimental study to treat a 50-year-old man with lifelong obesity. They were stimulating potential appetite suppressant sites in the hypothalamus, when the man suddenly announced that he was experiencing a feeling of "deja vu." He reported the perception of being in a park with friends from when he was around 20 years old. As the intensity of the electric stimulation was increased, the details became more vivid. As far as researchers could determine, the memory was entirely genuine.

Two months later, the researchers tested the man's memory again, with and without further stimulation, and found that after three weeks of continuous hypothalamic stimulation he showed significant improvements in two learning tests. In addition, the patient was much more likely to remember unrelated paired objects when stimulation was on than when it was off.

Their conclusion? "Just as DBS can influence motor and limbic circuits, it may be possible to apply electrical stimulation to modulate memory function and, in so doing, gain a better understanding of the neural substrates of memory."

This study is published online in the Annals of Neurology (, the official journal of the American Neurological Association.
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