Researchers are devising a new way to allow patients to control prosthetic devices by using their thoughts.

University of Pennsylvania researcher Douglas Smith and his colleagues envision the process this way: a piece of nerve tissue is connected to a person's nerve at one end, and a prosthetic device is connected at the other, thus enabling the person to control the device through their thoughts.

Schematic of stretch-grown axons, with axons growing on electrodes on right, and computer-controlled motor pulling axons to left.
(Douglas Smith/ University of Pennsylvania School of Medicine)

Their research was published in the January issue of Neurosurgery.

Smith, a professor of neurosurgery and director of the Center for Brain Injury and Repair at the university, characterized the development as an "extension cord" to link the brain and the device.

"We're at a junction now of developing a new approach for a brain-machine interface" after researchers grew 10 centimetres of nerve tissue attached to electrodes at one end, he said.

Smith's research envisions that the end without the electrodes would connect with a patient's nerve, relaying the signals to and from the electrodes, which would be connected to an electronic device.

"The nervous system will certainly rebel if you place hard or sharp electrodes into it to record signals. However, the nervous system can be tricked to accept an interface, letting it do what it likes — assimilating new nerve cells into its own network," Smith said.

The team used a new process to grow nerve fibres called axons between two plates, with one of the plates being a microchip coated with a substance attractive to nerve cells. The plates were slowly pulled apart over days, with a computer-controlled motor system determining the rate, until they reached 10 centimetres.

That was just the length the researchers picked. "I believe you could make this as long as you needed," Smith said. 

The researchers were able to detect and record signals sent over the fibres.

The team is now working on restoring motor activity in experimental animals.

Last year, researchers at a company called Cyberkinetics developed a sensor that enabled a paralyzed man to open e-mail or adjust the volume on a TV set using only his thoughts.