Brain Chip Helps Restore Muscle Movement

Nov. 2, 2006 — An implantable brain chip that serves as an artificial connection between nerve cells could one day help rehabilitate lost muscle movement in patients who have suffered brain injuries, stroke or paralysis.

"We found that when we put in these connections for long periods of time, we induce a reorganization of wiring in the brain," said Andrew Jackson, a senior research fellow in physiology and biophysics at the University of Washington in Seattle.

Jackson and his team reported their findings on the so-called Neurochip in a recent issue of the journal Nature.

Reorganizing the brain's wiring can be a long and frustrating process for people who have lost muscle use after an injury or stroke.

Typically, they must spend many hours doing physical exercises that encourage brain signals to find new pathways through healthy tissue.

But those new pathways are not always complete, which can translate into limited recovery of movement.

Or a given pathway may never form at all, which means the person has to find a completely new way to perform a task.

The Neurochip is designed to encourage the brain to build those pathways by stimulating nerve cells.

For the experiment, the scientists first mapped the brain activity of a healthy monkey and located two sites in the animal's motor cortex; one site made its hand move to the left and the other made its hand move to the right.

Next, the researchers attached a Neurochip to each site. About 6 centimeters in diameter, the chip contains two circuit boards and a battery, operating without wires to allow the monkeys to move freely.

"This neural chip was completely self-contained," said Andrew Schwartz, a professor of neurobiology at the University of Pittsburgh.

The team recorded the activity of nerve cells at a site responsible for moving the monkey's hand to the left. Whenever those nerves fired, the chip automatically delivered a stimulus to the second site, responsible for moving the monkey's hand to the right.

Under normal circumstances, these two sites would not be connected. But after a few days, the researchers conducted a test suggesting that the underlying neural connection between the two sites had been strengthened.

The test involved sending a series of electrical pulses to the original site. After the pulses, the monkey's hand moved right instead of left. The change may have been produced because the chip synchronized the activity between the two sites.

However, according to Schwartz, the test was "suggestive but not conclusive."

"They don't know why it happened or how it happened," said Schwartz. And it will take much more experimentation to confirm the artificial stimulus reinforced the connection, he said.

Jackson and his team hope to take the experiments further by establishing connections between more distant neural sites, such as between the brain and the spinal cord.