Newswise — Researchers at Duke University have demonstrated the feasibility of directly using human brain signals to operate external devices in patients who may not be able physically to control such devices with their hands. In their first human study of a brain-machine interface, researchers determined that arrays of electrodes are able to provide the vital signals encoding human hand movements that are necessary to control an external neuroprosthetic device.

The research team led by neurosurgeon Dennis Turner, MD, MA, and neurobiologist Miguel Nicolelis, MD, PhD; with lead author Parag Patil, MD, PhD, and Jose Carmena, PhD, will discuss their findings of "A Brain-Machine Interface: Ensembles of Human Subcortical Neurons Can Provide Signals for Neuroprosthetic Control." Their presentation is scheduled from 3:55 to 4:05 p.m. on Tuesday, May 4, 2004, during the 72nd Annual Meeting of the American Association of Neurological Surgeons in Orlando, Florida.

The research for this study further investigates earlier studies in the Nicolelis laboratory, which revealed that monkeys could use their brain signals to control a robotic arm. In the Duke study, brain signals were recorded from humans using an electrode array device, while each of the 11 volunteer patients played a hand-controlled video game.

Patient volunteers for this study suffered from either severe tremor or refractory Parkinson's disease. During neurosurgical operations performed to relieve the patients' symptoms, the authors recorded the brain's electrical signals with arrays of 32 microelectrodes, prior to placement of permanent electrodes. The permanent electrodes stimulate the brain using small electrical currents, resulting in improvement of the tremor or Parkinsonian symptoms. Patients generally remain awake during this type of surgery, and neurosurgeons record brain signals to ensure that the permanent electrodes are placed into the most effective location.

Patients were placed in a semi-sitting position in front of a video screen monitor. The patients then were given a squeeze ball that they held in one hand and were instructed to adjust their hand-gripping force to reach a target level of force as quickly as possible. Patients played the video game for up to 10 minutes during the surgical procedure. Researchers then explored the correlation between recorded neuronal activity and the patient's gripping force.

Researchers allowed each patient's shoulder and arm to rest on an armboard, so that the only motion used and measured for the task was the patient's gripping force. Overall, 61 percent of neurons from the subthalamic nucleus and 81 percent of neurons from thalamic motor areas varied with gripping force. The outcome of this study indicated that these signals could effectively predict each patient's hand motions. There were no intraoperative complications during the study.

"By simultaneously recording both neuronal activity and force generation, we could determine a correlation between neuronal activity and motor task performance since each could be observed and quantitatively defined," said Parag Patil, MD, PhD, a neurosurgery resident and lead author of the study.

Overall, the results of the study strongly suggest that subcortical motor areas may be able to provide additional sites from which the brain could control a human neuroprosthetic device.

"The results of this study are preliminary, but extremely promising," said Dennis Turner, MD, a senior author of the study. "A brain-machine interface that utilizes neuronal activity to control a neuroprosthetic devices could be life-changing for patients who suffer from severe neurological injury such as Parkinson's disease or for quadriplegic patients."

Currently, the research team is working to develop prototypical interfaces that would enable paralyzed people to operate neuroprosthetic and other external devices. The researchers report that examples of these potential devices might include a neurally controlled wheelchair or a neurally operated keyboard. Such devices also are expected to help those who have lost speech capabilities due to stroke or Lou Gehrig's disease.

In addition, the researchers have applied for approval to begin implanting experimental electrode arrays long-term in quadriplegic patients. The authors clearly emphasized that many years of development and clinical testing will be required before any neuroprosthetic devices are available to the general public.

Founded in 1931 as the Harvey Cushing Society, the American Association of Neurological Surgeons (AANS) is a scientific and educational association with more than 6,500 members worldwide. The AANS is dedicated to advancing the specialty of neurological surgery in order to provide the highest quality of neurosurgical care to the public. All active members of the AANS are certified by the American Board of Neurological Surgery, the Royal College of Physicians and Surgeons (Neurosurgery) of Canada or the Mexican Council of Neurological Surgery, AC. Neurological surgery is the medical specialty concerned with the prevention, diagnosis, treatment and rehabilitation of disorders that affect the entire nervous system including the spinal column, spinal cord, brain and peripheral nerves.

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American Association of Neurological Surgeons 72nd Annual Meeting