Paralyzing neurological diseases affect a quarter of a million people throughout the country, with clinical applications to treat these life-altering diseases seemingly light years away.

But a new study promises to close the gap and significantly reduce the distance, thereby bringing treatments much closer to the forefront.

The study in question, which appeared in the Oct. 15 online edition of Nature, had scientists at the Washington National Primate Center training monkeys to control the activity of single nerve cells in the motor cortex.

Neural activity was detected using a type of brain-computer interface and in this case, the electrodes were implanted in the motor cortex, which were connected via external circuitry to a computer. The neural activity led to movements of a cursor, as monkeys played a target-practice game.

After each monkey mastered control of the cursor, the researchers temporarily paralyzed the monkey's wrist muscles using a local anesthetic to block nerve conduction. Next, the researchers converted the activity in the monkey's brain to electrical stimulation delivered to the paralyzed wrist muscles.

The monkeys continued to play the target-practice game, only now cursor movements were driven by actual wrist movements – demonstrating that they had regained the ability to control the otherwise paralyzed wrist.

"What makes this research so exciting is that the neurons can be reprogrammed," Joseph Pancrazio, PhD, a program director at the National Institute of Neurological Disorders and Stroke (NINDS) told Medical Device Daily. "This study demonstrates a novel approach to restoring movement through neuroprosthetic devices, one that would link a person's brain to the activation of individual muscles in a paralyzed limb to produce natural control and movements."

NINDS funded the study, which was conducted by Eberhard Fetz, PhD, professor of physiology and biophysics at the University of Washington (Seattle) and an NINDS Javits awardee; Chet Moritz, PhD, a post-doctoral fellow funded by NINDS; and Steve Perlmutter, PhD, research associate professor.

Fetz's research is one of several lines of current neuroprosthetic research. Some investigators are using brain-computer interfaces to record signals from multiple neurons and convert those signals to control a robotic limb. Other researchers have delivered artificial stimulation directly to paralyzed arm muscles in order to drive arm movement – a technique called functional electrical stimulation (FES).

The Fetz study is the first to combine a brain-computer interface with real-time control of FES.

The research is an example of FES. Partially paralyzed people use FES devices now to let them stand, walk, use their arms and hands, and do other things. But they control those devices by flicking a switch, moving joints or tensing a muscle – even, say, the muscle that enables them to wiggle an ear.

"In order to use this on a paralyzed individual, we don't need to know what neurons to go after," Pancrazio told MDD.

Up until Fetz' findings, brain-computer interfaces were designed to decode the activity of neurons known to be associated with movement of specific body parts. Here, the researchers discovered that any motor cortex cell, regardless of whether it had been previously associated with wrist movement, was capable of stimulating muscle activity. This finding greatly expands the potential number of neurons that could control signals for brain-computer interfaces and also illustrates the flexibility of the motor cortex.

The team found that the monkeys' control over neuronal activity – and the resulting control over stimulation of their wrist muscles – improved significantly with practice. According to the results practice time was limited by the duration of the nerve block.

Comparing the monkeys' performance during an initial two-minute practice and a two-minute peak performance period, the scientists found the monkeys successfully hit the target three times more frequently and with less error during the peak performance. In the future, greater control could be gained by using implanted circuits to create long-lasting artificial connections, allowing more time for learning and optimizing control, according to Fetz.

The researchers also found that the monkeys could achieve independent control of both the wrist flexor and extensor muscles.

The group was able to use the pattern of activity in about 100 brain cells to discern the wrist movement a monkey wanted to make.

The end results are able to establish a connection between the motor cortex and sites in the spinal cord below the injury, people with spinal injuries may be able to achieve coordinated movements.

"In 25 years from now, I would see a patient with high spinal injuries incapable of moving their hands or arms – the technology would be at a point where we can restore the control of both arms," Pancrazio said. "I see this as such a transformative therapy."