From here, research moved to primates, because their brains and limb structure are the similar to those of humans.  Researchers have used electrode array recordings coupled with complex algorithms to predict 3-D arm movements in primates.  In November of 2000, Wessberg et al reported in Nature that, through recordings from large neuron populations in the motor cortex of owl monkeys, signals were developed that could successfully control a robotic arm in real time, both locally and across the Internet. One arm was at Duke University, where the study was carried out, while the other was a remote robot arm at MIT. In both cases, the signal processing allowed for successful control of robot arms.

NMP Schematic

(Nature)

The group also showed that implanted microwires can provide usable recordings for at least two years. They concluded that their study indicates that recordings obtained from populations of neurons in the motor cortex of the monkey's brain might be able to control a complex prosthetic limb for many years, via real time transformations of signals from implanted electrodes.

The most recent advance in neuromotor prosthetics was published by researchers at Brown University in the March 2002 Nature. In this experiment, it was shown that information from monkey motor cortex neurons, obtained from an electrode array, could be transformed into a signal which the monkey could use without training to move a computer cursor.

Three monkeys were implanted with an electrode array. The monkeys manipulated a joystick to move a computer cursor around the screen. Using only neural information recorded while each monkey moved the cursor, the research team found they could reconstruct the path of each monkey’s hand.  In a subsequent part of the study, monkeys could use either hand control or neural control to play a game called 'pinball,' where they would touch their cursor to a randomly appearing dot. The monkeys immediately began to play by neural control, and required no extra training to track targets without a joystick. Upon analysis of the experiment, it was discovered that neural control of the cursor was almost as good as joystick control, although brain control was found to be a little bit slower.

Video clips of 'pinball':
(Courtesy of John Donoghue)

Clip one: The monkey moves the joystick cursor (blue-gray) and the neural control cursor (green) to tag the red target.

Clip two: The monkey leaves the joystick still while still tracking the target by neural control.

The researches also wrote that the electrode array used in this study is suitable for human use and that their results suggest that control of neuromotor prosthetic limbs may eventually be a reality for human patients with paralysis.

The success of neuromotor prosthetics in animal models suggests that this technology will someday be used to treat paralyzed humans. But how far are we from this? Obtaining FDA approval for any device can be an extremely long process, not to mention that the jump from moving a robotic arm in one dimension or a cursor in monkey to the successful control of a complex three dimensional prosthetic limb in humans would be a huge transition. It is impossible to say if, when, and how this technology will be available for human use, but it seems that researchers believe it can and will happen.