US scientists demonstrate brain-directed robotic arm

Scientists in the US claim to have developed a brain-directed robotic arm with greater levels of control and movement than has ever been demonstrated before.

Researchers from Pittsburgh University implanted two microelectrode arrays into the brain of a 52-year-old tetraplegic woman that connected her neurons via wires to the electronic circuitry of a robotic arm placed next to her.

After 14 weeks of training, she was able to move the wrist and hand unaided to perform tasks such picking up and moving a range of different-shaped items, with a success rate of up to 91.6 per cent and more than 30 seconds more quickly than at the start of the trial.

Prof Andrew Schwartz, lead author of the report on the work published today on the website of medical journal The Lancet, said the patient’s unprecedented speed of adaptation to the prosthesis was partly attributable to innovations in how it was connected to her brain.

‘In developing mind-controlled prosthetics, one of the biggest challenges has always been how to translate brain signals that indicate limb movement into computer signals that can reliably and accurately control a robotic prosthesis,’ he said in a statement.

‘Most mind-controlled prosthetics have achieved this by an algorithm that involves working through a complex library of computer-brain connections.

‘However, we’ve taken a completely different approach here, by using a model-based computer algorithm that closely mimics the way an unimpaired brain controls limb movement.

‘The result is a prosthetic hand that can be moved far more accurately and naturalistically than previous efforts.’

The patient was assessed using the action research arm tests (ARATs) typically used to assess limb function in people who have suffered paralysing events such as strokes.

In particular, they assessed her ability to move the arm with what is known as seven degrees of freedom: moving from one point to another in three dimensions, orientating in three dimensions and grasping in one dimension.

According to the researchers, the next steps in developing the technology will include adding sensory elements so that the patient can feel the difference between hot and cold or smooth and rough surfaces and developing wireless technology to link the arm and brain implant.

Commenting on the research, Prof Grégoire Courtine of the Swiss Federal Institute of Technology Lausanne (EPFL) said: ‘This bioinspired brain-machine interface is a remarkable technological and biomedical achievement.

‘Although plenty of challenges lie ahead, these sorts of systems are rapidly approaching the point of clinical fruition. Through concerted efforts, and by ensuring that various different strategies available are optimally combined, these kinds of prosthetics might soon become revolutionary treatment models for sensorimotor paralysis.’