SmartHand is a European collaborative project to develop a next-generation robotic prosthetic limb, and as part of the project Swedish researchers have successfully demonstrated a neat psychological trick that makes wearers feel like an artificial limb is actually part of their body.
A report published by the team at the Karolinska Institutet and Malmö University Hospital shows success in what’s known as the “rubber hand” illusion. Amputees’ brains can be fooled into thinking that a fake hand is actually wired into their nervous systems, despite the fact that the hand has no sensory inputs whatsoever.
It’s a similar effect to the solution discovered by V.S. Ramachandran to alleviating phantom limb pain: In his work the brain is fooled into thinking it’s getting sensory inputs from a missing limb by an optical illusion with a mirror, and the mental side-effects of this relieve pain. The work challenged the existing medical thinking that damaged severed nerve endings were the cause of the pain.
In the Swedish case, Prosthetic limb users were subjected to a different visual trick: Someone visibly touched the artificial hand while out of the patient’s sight their arm stump was being stimulated. Apparently the illusion is very convincing, and the deep psychological basis for the effect was further demonstrated by subconsciously-induced sweating when the “rubber” hand was pricked by a needle. The results suggest that the artificial hand has been completely adopted into the user’s body image at a neurological level.
The research team sees this as evidence for a possible new way of connecting up future prosthetic limbs sensor-equipped hands to a patient, and it’s potentially a much simpler solution than having to directly couple electronics into the nervous system surgically. And since the illusion is similar to Ramachandran’s study, there’s a possibility that phantom limb pain may also be reduced.
The research into the more mechanical aspects of SmartHand have produced an amazing thought-controlled product that’s ever-evolving, with the goal of totally replacing a missing forelimb with a sophisticated robot. But it’s not alone: in the US there’s Dean Kamen’s robotic limb project.
This device is already so sci-fi-ishly sophisticated it’s been dubbed the “Luke arm” after the artificial limb given to Luke Skywalker in the Star Wars movies. Kamen’s project is concentrating on developing the motorized engineering and nerve-input interface–it’s directly wired into patient’s nerves to control its motors–but has already shown remarkable results. Famously one test subject felt so much at ease operating the arm that he was able to rest a mug on a nearby table without watching, and carrying on a conversation at the same time.
Kamen’s work was initially aimed at replacing limbs lost by soldiers on duty, but the Luke arm and SmartHand suggest that limb-loss victims of all types, through accidents and as civilian war casualties, have amazing artificial limbs to look forward to in the future. They’ll work just like the real thing, maybe even being stronger, and they just might feel like they’re a natural part of the body. But the costs will have to be driven down from multi-million-dollar levels.