"We initially used subcortical electrodes, because they are more stable because they are buried deeper," said Turner. Also, he said, the deeper regions present other advantages. "The way the brain works, all the signals for motor control are filtered through these deep regions of the brain before they reach the final cortical output," he said. "So, they are theoretically easier to record from than cortical areas. The subcortical areas are also denser, which means there are more cells to record from in a smaller area.
Working with Duke biomedical engineers, the research team is currently developing the initial prototype of a neuroprosthetic device that will include a wireless interface between the patient and the device.
According to Turner, while the most obvious application of such technology would be a robot arm for a quadriplegic, he and his colleagues are planning other devices as well. One would be a neurally controlled electric wheelchair, and another a neurally operated keyboard, whose output could include either text or speech. Such devices could help both paralyzed people and those who have lost speech capabilities because of stroke or amyotrophic lateral sclerosis (Lou Gehrig's disease).
A key question in future clinical studies will be whether humans can incorporate such devices into their "schema," or neural representation of the external world, said Turner. The monkeys in Nicolelis' studies appeared to do just that.
"We do know that for all kinds of motor training, such as riding a bicycle, people incorporate an external device into their schema, and the process becomes subconscious," he said. "We will build on that phenomenon in our human studies. It's known, for example, that patients who don't have use of their arm still show in MRI studies that the control centers in the brain are working normally. When they are asked to imagine moving their arm, the control centers become acti
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Contact: Dennis Meredith
dennis.meredith@duke.edu
919-681-8054
Duke University Medical Center
23-Mar-2004