Paralyzed Man Feels Again After Scientists Stimulate His Brain With Electrodes

A man with paralyzed limbs was able to feel sensations in his arm thanks to scientists who stimulated his brain with electrodes, in what was believed to be a world first.

Researchers at California Institute of Technology (Caltech) hope their work will one day enable patients with paralysis to feel sensations through sensors in prosthetic limbs.

Three years ago, the patient was paralyzed from the shoulders down after suffering an injury to his spinal cord. As documented in the study published in the journal eLife, researchers harnessed a part of his brain called the somatosensory cortex to induce natural sensations in his arm.

The somatosensory cortex is the part of the brain in charge of how we process movement and space, as well as sensations such as pressure and vibrations.

"It was quite interesting," the participant said in a statement. "It was a lot of pinching, squeezing, movements, things like that. Hopefully it helps somebody in the future."

Building on previous studies that used neural implants to create a tingling or buzzing feeling in the hand, the scientists were able to promote natural sensations similar to those the patient had felt before his injury. That included squeezing, tapping and the feeling that his arm was moving upward. The team achieved this by implanting small electrodes into his somatosensory cortex, which they used to send pulses of electricity into his brain. When the scientists changed the frequency, amplitude and location of stimulation to the implants, the sensations the man felt would change, too.

The team believes this is the first time natural sensations have been induced by stimulating the intracortical part of the brain.

Further research is needed to understand how neural codes control different physical sensations. The team also hopes to pinpoint how to stimulate the somatosensory cortex to create specific feelings. If successful, the researchers will incorporate the technology into prosthetic limbs so patients can feel again.

"Currently the only feedback that is available for neural prosthetics is visual, meaning that participants can watch the brain-controlled operation of robotic limbs to make corrections," lead author and Caltech professor of neuroscience Richard Andersen said in a statement.

"However, once an object is grasped, it is essential to also have somatosensory information to dexterously manipulate the object. Stimulation-induced somatosensory sensations have the potential added advantage of producing a sense of embodiment; for example, a participant may feel over time that the robotic limb is a part of their body."