Currently, paralyzed individuals have the ability to regain limited mobility via brain-machine interfaces, which respond to signals in the brain and translate them into movement. The brain-machine is usually an external device, such as a robotic arm.

Researchers at Cornell University have developed a new model for brain-machine interfaces that allows paralyzed patients control their extremities through brain activity alone.

The new technology utilizes the fact that in paralyzed patients the brain's motor cortical areas are still active, it's only the pathway from the brain to the rest of the body that is disrupted. Sensor implants in the motor cortical areas allows neural activity to be recorded and then translated to the desired movement using a "mathematical transform called the decoder," according to a press release describing the findings.

In their paper, published in Nature Communications, Maryam Shanechi, assistant professor of electrical and computer engineering and Ziv Williams, assistant professor of neurosurgery at Harvard Medical School describe a spinal prosthesis that helps the brain direct "targeted movement" to paralyzed limbs. The researchers demonstrated the new technology by connecting two subjects and having one subject "move" a limb in the other subject using their neural impulses.

In the experiment, one animal controlled the movement by deciding which location on the other animal to activate, thereby generating the associated neural activity. Algorithms then decoded the neural signals and electrically stimulated the second animal's spinal cord, causing the animal's target limb to move.

"The problem here is not only that of decoding the recorded neural activity into the intended movement, but also that of properly stimulating the spinal cord to move the paralyzed limb according to the decoded movement," Shanechi said.

The experiment is the first of its kind to use two separate animals to test paralysis movement, instead of one animal with a temporarily paralyzed limb. In this way the scientists show that they can translate neural activity between animals that have no physiological connection. This is exactly the case for paralyzed individuals.