Artificial touch boosted by brain-controlled bionic hand

New research suggests that a complex sense of touch for people with spinal cord injuries is now a step closer.

For individuals living with a spinal cord injury, the electrical signals coming from the hand to the brain that should allow an individual to feel tactile sensations, are being blocked by the injury and that sense of touch is lost. A bionic limb controlled by user’s brain signals can bring back some functionality and independence to someone with a paralysed hand.

Published in Science, a new study paves the way for complex touch sensation through brain stimulation, while using an extracorporeal bionic limb that is attached to a chair or wheelchair. Previously, a bionic hand would not be perceived by the user as part of the body, since it would not provide any sensory feedback like a biological hand. This study aimed to improve the usability of an extracorporeal bionic limb, which would be mounted on a wheelchair or similar equipment close by to the user.

The researchers, who are all part of the US-based Cortical Bionics Research Group, have discovered a unique method for encoding natural touch sensations of the hand via specific microstimulation patterns in implantable electrodes in the brain. This allows individuals with spinal cord injuries not only to control a bionic arm with their brain, but also to feel tactile edges, shapes, curvatures and movements, that until now have not been possible.

“In this work, for the first time the research went beyond anything that has been done before in the field of brain–computer interfaces (BCI). We conveyed tactile sensations related to orientation, curvature, motion and 3D shapes for a participant using a brain-controlled bionic limb. We are in another level of artificial touch now. We think this richness is crucial for achieving the level of dexterity, manipulation, and a highly dimensional tactile experience typical of the human hand,” said Giacomo Valle, lead author of the study and Assistant Professor at Chalmers University of Technology, in Sweden.

For the study, two BCI participants were fitted with chronic brain implants in the sensory and motor regions of the brain that represent the arm and hand. Over the course of several years, the researchers were able to record and decode all of the different patterns of electrical activity that occurred in the brain related to motor intention of the arm and hand. Decoding and deciphering brain signals with this technology is unique and allows the participants to directly control a bionic arm and hand with the brain for interacting with the environment.

This research is just the first step towards patients with spinal cord injuries being able to feel this level of complex touch. In order to capture all the features of complex touch that the researchers are now able to encode — and convey to the user — more complex sensors and robotic technology are needed (for example, prosthetic skin). The implantable technology used for stimulation would also require development to increase the repertoire of sensation.

Image credit: iStock.com/Viorel Kurnosov