Wiring the Mind
Each year thousands of people become prisoners in their own bodies when paralyzed by stroke, disease, or injury. Philip Kennedy believes he's found a way to free these victims of "locked-in syndrome."
The key is what he calls a neurotrophic electrode—a hollow glass cone filled with recording wires and chemicals that promote nerve growth. When the electrode is placed in the motor cortex of the brain and hooked to a computer, it allows a patient to move a cursor across a computer screen, putting him or her once again in touch with the outside world.
The growth-inducing chemicals in the tip of the glass cone beckon the brain's cells into the electrode, where they link up with the recording wires. "I realized that to generate an electrode to be stable over the lifetime of the patient," Kennedy explains, "we need the brain to connect into the electrode, instead of trying to get the electrode into the brain."
Once the link is made, electrical activity in the implanted area of the brain is picked up by the wires and transmitted to a receiver and amplifier. The patient can learn to control these signals and use them, like a mouse, to move a cursor. A biofeedback system generates noises that "indicate when the brain is thinking in a way that will allow a person to focus on the cursor," Kennedy says.
His first subject, a woman suffering from amyotrophic lateral sclerosis (the same disease that afflicts physicist Stephen Hawking), learned to turn the signal on and off but died from her disease shortly thereafter. This year, Kennedy and neurosurgeon Roy Bakay implanted electrodes in another subject—a 53-year-old man who had suffered a stroke in the brain stem. He is now able to move the cursor horizontally across the screen and pick out icons that prompt the computer to speak commonly used phrases.
Soon Kennedy hopes to use signals from neurotrophic electrodes to control electrical stimulators attached to a patient’s paralyzed muscles, bypassing the signal block created by spinal cord injury. In addition, he notes, the electrode can be used to study brain function. "Never before," he says, "have recordings been made from a human brain for so long and with such stability of the recorded signals."
INNOVATOR: John Sabolich, Sabolich Research and Development
Prosthetics can restore some of the mechanical abilities of a missing limb but none of its sensations. Lack of feeling condemns the wearer to a life of uncertainty: Is the ground too uneven for safe walking? Is the baby’s bath water warm and not scalding hot?
John Sabolich, a second-generation prosthesis engineer, created the Sabolich Sense of Feel System and Hot & Cold Sensory System to help put such questions to rest.
The Sense of Feel System "reads" the ground using pressure sensors implanted in a prosthetic foot. The sensors transmit information to electrodes pressed against the base of the residual limb. The electrodes in turn stimulate the nerve endings in the skin; the greater the pressure on the sensors, the more intense the stimulus. At first the signal feels like a tingle, but soon the brain learns to interpret it as pressure. Eventually, Sabolich says, some prosthesis wearers begin to experience the sensations as if they were coming from the lost foot.
The Hot & Cold Sensory System works in much the same way, using temperature sensors in place of pressure sensors. Thermal readings from the sensors are used to heat or cool a plate pressed against the skin, so the amputee can easily interpret the signal.
INNOVATOR: William Craelius, Rutgers University
When Jay Schiller lost his hand in an accident, even the simplest manual task became frustrating. But last year he sat down at the piano and played "Mary Had a Little Lamb," nimbly moving one artificial finger at a time.
It was a proud moment for William Craelius, inventor of the tendon-activated pneumatic artificial hand that made Schiller’s performance possible. The hand has a plastic socket that encases an amputee’s upper limb. Sensors in the socket respond to movements of the remaining tendons in the limb. The device relies on a sort of muscular memory: the wearer moves the prosthetic fingers by activating the same tendons originally used to move real fingers. When it picks up a tendon twitch, a limb sensor signals a computer activator to move part of the hand.
"For most subjects," says Craelius, "the training is simple. They simply command a particular finger to move. The sensor detects the command, the computer decodes it, and the finger moves."