Monday, May 1, 2006

Tiny Electrodes for the Brain

Nanowires could make brain-machine interfaces safer and cochlear implants more effective.

By Kevin Bullis

NYU and MIT researchers have developed a flexible electrode that can send or receive signals from brain cells. The electrode can be inserted into the brain through blood vessels, eliminating the need to open a patient's skull for some neurological treatments. (Courtesy of Zina Deretsky, National Science Foundation.)

A new type of polymer nano electrode could make brain implants, including those used to treat severe cases of Parkinson's, far safer, and it could also make attempts to restore vision and movement with direct brain-machine interfaces more feasible. Rodolfo Llinas, professor of neuroscience at New York University, and researchers at MIT have developed a nanowire electrode just 600 nanometers wide that can send and receive signals to the brain.

The electrode developed by Llinas and coworkers is so small that it could be inserted through an artery, perhaps in the arm or groin, and threaded up to the brain. Because the electrode is a small fraction of the size of a red-blood cell and flexible, it can be snaked through the smallest blood vessels, getting close enough to neurons deep in the brain to detect and deliver electrical signals.

[Click here for images of the electrode in blood vessels.]

One current treatment for severe cases of Parkinson's, called deep brain stimulation, involves implanting electrodes that deliver high-frequency electrical pulses which shut down parts of the brain responsible for the disease's symptoms (see "Brain Pacemakers"). Such treatments, however, are risky and expensive, in part, because they require that a patient's skull be opened to surgically insert electrodes into brain tissue.

The conventional electrodes, which now measure in millimeters, can also damage blood vessels in the brain, says Joseph Pancrazio, program director for neural engineering projects at the National Institute of Neurological Disorders and Stroke (NINDS), one of the National Institutes of Health. "By taking advantage of the nanodimensions to thread the electrodes through the vasculature, you may reduce the risk of stroke," he says. "This is a completely out-of-the box way to think about enabling deep-brain stimulation. I think there may be payoffs in terms of safety, efficacy, robustness, and biocompatibility. It certainly is an area that we need to look at seriously."

"Not having to open the skull would be a clear benefit over what we're now doing," says Jeff Bronstein, neurologist at the UCLA Medical School, who says thousands of Parkinson's patients have undergone the deep brain stimulation procedures.

John Heiss, a neurosurgeon at NINDS, cautions that it will first be necessary to demonstrate that the nanowires do not cause complications, such as blood clots. He also notes that, although the head would not need to be opened, such a procedure would still require some invasive surgery. Heiss says, however, that if the procedure proves to be safe, it could make deep brain stimulation a more attractive alternative at earlier stages of Parkinson's.