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22-04-2012 | Physical rehabilitation | Article

Brain stimulation restores hand grasp after paralysis

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MedWire News: Research shows that a voluntary hand grasp motion can be restored after paralysis by bypassing the spine and carrying out functional electrical stimulation (FES) of the brain.

"We are eavesdropping on the natural electrical signals from the brain that tell the arm and hand how to move, and sending those signals directly to the muscles," said study author Lee Miller (Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA) in a press statement.

"This connection from brain to muscles might someday be used to help patients paralyzed due to spinal cord injury perform activities of daily living and achieve greater independence."

The researchers triggered temporary paralysis using local anesthetic injected into the elbow in rhesus monkeys, thus mimicking the type of injury that might be caused by C5 or C6 spinal cord injury.

Using previously gathered information from 100 neurons in the motor cortex and in the arm, the researchers obtained information on neuron activity and used it to predict how the monkey's arm muscles would normally be stimulated to grasp an object.

They then applied a similar amount of artificial stimulation to an array of electrodes implanted in the area of the monkey's motor cortex involved in controlling arm movements to trigger the hand grasp response artificially. The process was successful and the monkeys were able to pick up a ball nearly as well as they had prior to the anesthetic injection.

"The monkey won't use his hand perfectly, but there is a process of motor learning that we think is very similar to the process you go through when you learn to use a new computer mouse or a different tennis racquet. Things are different and you learn to adjust to them," said Miller.

Writing in Nature, the team explains that the findings are "a major advance towards similar restoration of hand function in human patients through brain-controlled FES."

They explain that the process bypasses the spinal cord and restores voluntary control to paralyzed muscles.

Miller and colleagues believe that such a neuroprosthesis would allow a "more flexible and dexterous" use of the hand than is possible with current technology for paralyzed patients with conditions such as tetraplegia.

"We can extract a remarkable amount of information from only 100 neurons, even though there are literally a million neurons involved in making that movement," said Miller.

"One reason is that these are output neurons that normally send signals to the muscles. Behind these neurons are many others that are making the calculations the brain needs in order to control movement. We are looking at the end result from all those calculations."

By Helen Albert

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