( Brain pacemakers that have helped ea...)How brain pacemakers erase diseased messages

Brain "pacemakers" that have helped ease symptoms in people with Parkinson's disease and other movement disorders seem to work by drowning out the electrical signals of their diseased brains.

Despite the clinical success of the devices, which have been approved by the Food and Drug Administration and can be found in the heads of about 30,000 Americans, the mechanisms by which deep brain stimulation alleviates disease symptoms aren't well understood.

Biomedical engineers at Duke University's Pratt School of Engineering have found that stimulation administered by rapid-fire electrical pulses deep in the brain produces what they call an "informational lesion." By relaying a repetitious and therefore meaningless message, constant pulses overwhelm the erratic bursts of brain activity characteristic of disease.

"Periodic bursts in the brains of people with tremor -- which might follow a pattern such as 'pop-pop-pop, silence, pop-pop-pop, silence' -- propagate pathological information within brain circuits," said Warren Grill, the study's lead investigator and an associate professor of biomedical engineering. "If you replace that instead with a constant 'pop-pop-pop-pop-pop-pop,' you've erased that pathological information."

Grill said the high-frequency deep brain stimulation acts like a surgical lesion, another acceptable treatment for severe tremor disorders and epilepsies. But the electronic device has the advantage of being adjustable or reversible.

The researchers' report appears in a special June 2007 issue of the journal IEEE Transactions on Neural Systems and Rehabilitation Engineering, edited in part by Grill. The study was conducted by a team that included Alexis Kuncel, a doctoral student in biomedical engineering at Duke, and Scott Cooper, a neurologist at the Cleveland Clinic, with support from the National Institutes of Health.

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Source:Duke University