Using computers for checking e-mail, drawing images and playing games seem like common tasks for most people. For the severely paralyzed, however, these undertakings can be beyond their reach.
Neurotechnology -- using technology to study the brain -- relies on methods such as CAT (computed axial tomography) scans and deep brain stimulation. In deep brain stimulation, medical devices are placed on the brain in an effort to control brain activity and aid another part of the body.
This use of neurotechnology can stop the tremors of people with Parkinson's disease, while cochlear devices can restore hearing. While these examples of neurotechnology insert information into the brain, other applications of the technology involve extracting information from brain signals via neural interfaces, or a communication link set up between a brain and a device, like a computer. This field holds promise for helping paralyzed people reconnect with the world.
For some people participating in a clinical trial of BrainGate, a neural interface system developed by Cyberkinetics Neurotechnology Systems of Foxborough, Massachusetts, that connection has already occurred.
"Many neurological disorders disrupt the ability to move, but leave cognition intact," said John Donoghue, founder, chief scientific officer and director of Cyberkinetics, during a recent talk on his company's technology at Boston's Museum of Science. "Think spinal cord injuries, something else that cuts the brain off from the body. The signals remain years after the injury."
Converting this cognition into action requires reading brain signals, which communicate messages from the brain to the nerves. Neurons, using electrical impulses, handle the task of sending communications from the brain to the body. These impulses resemble spikes when displayed on a monitor.
"All the information in the brain is based on these spikes putting out information," Donoghue said. "When you think movement, intention goes from the brain to nerves to muscles."
Of course, with paralyzed patients these intentions never develop into an action.
Cyberkinetics' technology decodes these electrical impulses into the corresponding action, with participants performing tasks such as moving a cursor or spelling out words on a monitor, all by thought. Picking up the brain's electrical impulses requires placing microelectrode sensors on the brain's motor cortex, a section of the cerebral cortex that controls motor functions.
The sensor, a square chip the size of a child's aspirin, is placed on the brain via a hole that is drilled into the skull. The sensor, which contains 100 electrodes that are thinner than a human hair and measure 1 millimeter long, is imbedded 1 millimeter into the brain.
"The only way to pick up signals is to place microelectrodes up close to our nerve cells," Donoghue said.
A bundle of gold wires connects the sensor to a pedestal, which protrudes through the scalp. Cables connect the pedestal to a cart containing a computer array, which analyzes the brain data and translates it into a corresponding motion.
When connected to a PC, some patients in BrainGate's clinical trial have been able to check e-mail by thinking about moving a cursor displayed on a monitor, as well as play a video game by thinking about moving an on-screen paddle. Another patient "spoke" for the first time after the person used a word processing program to form sentences.
BrainGate can also be connected to prosthetic devices and other peripherals. One patient opened and closed a prosthetic hand with thought, and picked up and moved objects with the aid of a robotic arm.