Complex algorithm advances mind-controlled prosthetic arm

Over the course of 13 weeks, a woman paralyzed from the neck down learned to guide a robotic arm with her thoughts with a level of agility closer to normal than in previous studies, according to researchers at the University of Pittsburgh. The work is considered one step closer to creating functional mind-controlled prosthetics for people with paralysis.

A paper published online this week in The Lancet describes her progress, from merely being able to move the arm freely on the second day to eventually refining its movements to accomplish tasks of daily living.

Two tiny electronic chips, each with 96 electrodes, was implanted in the woman's motor cortex, the region of the brain that initiates movements. The number of electrodes is double that of a Brown University study in which a paralyzed woman was able to use a robotic limb to perform tasks such as giving herself a drink of coffee, reports MIT Technology Review.

The Pittsburgh group reported 91.6 percent accuracy in performing target-based reaching tasks at 13 weeks, as well as improvements in speed and efficiency.

Michael Boninger, a member of the research team, told Reuters the main advance was in the complex algorithm that translates the brain signals from thought to action with the robotic limb.

"There is no limit now to decoding human motion," he said. "It gets more complex when you work on parts like the hand, but I think that, once you can tap into desired motion in the brain, then how that motion is effected has a wide range of possibilities."

The team plans to make a wireless version of the brain-machine interface, and to incorporate sensory feedback. The robotic arm has more than 100 sensors that can detect vibration, pressure, temperature, and other sensations. They also plan to work with more patients to develop a model that can be put to therapeutic use.

Rice University, the University of Houston and TIRR Memorial Hermann Hospital are working on a noninvasive brain-machine interface to a robotic orthotic device to help rehabilitate stroke patients' upper limbs. A similar device already is used to treat spinal-cord injury patients. The technology allows a stroke patient to operate an exoskeleton that wraps around the arm from the fingertips to the elbow.

Meanwhile, the University of Calgary is pairing robots and stroke patients in a totally different way. Robots are used to help assess post-stroke impairments in patients and adjust treatment regimens.

To learn more:
- read the abstract
- here's the Technology Review article
- check out the Reuters story