14 DAY TRIAL // A multi-institutional team of researchers has found that people with long-standing, severe paralysis can generate signals in the area of the brain responsible for voluntary movement and these signals can be detected, recorded, routed out of the brain to a computer and converted into actions -- enabling a paralyzed patient to perform basic tasks. The brain-computer interface, or the "neuromotor prosthesis", is called the BrainGate Neural Interface System, and it was developed by Cyberkinetics Neurotechnology Systems, Inc., of Foxborough, Mass.
The BrainGate System consists of a 4x4 millimeter sensor, about the size of a baby aspirin, with 100 tiny electrodes, each thinner than a human hair. The sensor is implanted on the surface of the area of the brain responsible for voluntary movement, the motor cortex. The electrodes penetrate about 1 mm into the surface of the brain where they pick up electrical signals -- known as neural spiking, the language of the brain -- from nearby neurons and transmit them through thin gold wires to a titanium pedestal that protrudes about an inch above the patient's scalp. An external cable connects the pedestal to computers, signal processors and monitors.
Researchers present the first results from the initial participants in a clinical trial in the 13 July 2006 issue of Nature. The first patient, Matthew Nagle, a 25-year-old Massachusetts man with a severe spinal cord injury, has been paralyzed from the neck down since 2001. After having the BrainGate sensor implanted on the surface of his brain at Rhode Island Hospital in June 2004, he learned to control a computer cursor simply by thinking about moving it.
During 57 sessions, from July 2004 to April 2005, at New England Sinai Hospital and Rehabilitation Center, Nagle learned to open simulated e-mail, draw circular shapes using a paint program on the computer and play a simple video game, "neural Pong," using only his thoughts. He could change the channel and adjust the volume on a television, even while conversing. He was ultimately able to open and close the fingers of a prosthetic hand and use a robotic limb to grasp and move objects. Despite a decline in neural signals after 6.5 months, Nagle remained an active participant in the trial and continued to aid the clinical team in producing valuable feedback concerning the BrainGate technology.
The second patient, a 55-year-old man with a similar injury, had the sensor implanted by surgeons at the University of Chicago in April 2005 and was followed by researchers from the Rehabilitation Institute of Chicago and Cyberkinetics. Although his device initially had electrical problems, these were repaired and he was able to learn to control the cursor from months seven through 10 of the trial, until a technical issue caused signal loss at most electrodes after 11 months.
"The results," said senior author of the paper, John Donoghue, professor and director of the brain science program at Brown University and chief scientific officer of Cyberkinetics, "hold promise to one day be able to activate limb muscles with these brain signals, effectively restoring brain-to-muscle control via a physical nervous system."
The current BrainGate System is still in its infancy and is far from perfect. It is bulky and cumbersome. The quality of the signal can vary from patient to patient and from day to day. A great deal of work remains to be done to extend the longevity and reliability of the sensor. Patient two never developed as much control as Nagle, and even Nagle's level of control, the authors note, "is considerably less than that of an able-bodied person using a manually controlled computer cursor."
"Training patients to move things with their minds is different with each patient," said Maryam Saleh, who worked with the first two patients as a Cyberkinetics technician and is now a doctoral student in Hatsopoulos's Chicago lab.
The system is constantly being improved. Next steps include faster and more precise algorithms to help the computer keep pace with the neuronal inputs, and a more portable wireless system. The researchers are also looking at new applications, such as enabling the brain-computer combo to control a wheelchair or other gadgets that will restore some control and freedom to patients with severe paralysis.
"Our researchers initiated the clinical trial with the hope of being able to develop a non-obtrusive system that would one day provide more freedom to those with severe paralysis," said Timothy Surgenor, president and CEO for Cyberkinetics. "We are eager to expand on this initial proof-of-concept toward one day providing improved independence and overall quality of life."
"As a physician," said Harvard's Leigh R. Hochberg, lead author of the Nature paper and a principal investigator in this pilot trial, "I do whatever I can to optimize the recovery of patients with paralyzing disorders such as stroke, spinal cord injury or neuromuscular disease. The available assistive technologies, however, provide neither sufficient independence nor mobility.
"Thanks to the generosity and pioneering spirit of our initial trial participants, who have volunteered without expecting to derive any personal benefit, important progress is being made in developing a real-time neuromotor prosthesis," Hochberg said. "Though much work remains to be done, hopefully one day, I'll be able to say: 'We have a technology that will allow you to move again.'"
