Guitar Hero Trains Amputees on the Use of Artificial Arms

The use of technology as a means to aid people with disabilities can sometimes occur in surprising contexts. As an example, consider a recent research project presented yesterday at the IEEE Biomedical Circuits and Systems Conference in Baltimore. Rehabilitation therapists have repurposed the popular Guitar Hero game into a tool for amputees to develop facility with prosthetic limbs.

The project, sponsored by the U.S. Defense Advanced Research Projects Agency (DARPA), is founded on the principle that residual muscles in the arm can retain some nerve control after an amputation. If the nerves are rerouted and bound to an interface that can detect electromyographic signals, the user can control a mechanical arm as if it were biological.

I won’t pretend to fully understand the science behind these remarkable findings; my primary interest is in the use of virtual-reality training to replicate the user’s experience. Patients are asked to perform such repetitive actions as opening and closing fingers, and the system records the corresponding signals. These are mapped to an algorithm and calibrated, which apparently is no easy task:

[It's] a lot harder than it might seem. The trouble comes when the myoelectric impulses of one finger need to be separated from the others. Press your thumb against your middle finger, and you’ll see the problem. If you can’t even easily actuate separate fingers with your native hand, how exactly is an algorithm supposed to figure out an amputee’s intentions from muscles in the chest or upper arm? And, because a movement might be slightly different every time you do it, it needs to be repeated countless times during training for the control algorithm to latch onto the essential signal.

Those of us who work in the user experience field understand the importance of keeping the interest of a test subject. It can be a long, tedious process requiring a high level of concentration. Upon discovering the same challenges with their volunteers, DARPA invented a rather novel way to maintain the integrity of the research while making it fun for the subjects.

Engineers Rober Armiger and Jacob Vogelstein borrowed a copy of Guitar Hero from a colleague, ripping out the guts of the controller and rewiring the interface to one input that could be triggered by a muscle contraction. The demo was tested on three volunteer users with normal limb control, then on an Iraq veteran who had lost his right hand in combat.

This excites me on many fronts. One item of interest is the attention paid by the designers towards attaining a measurable outcome. The benefit of any haptic interface (which I’ve written about before) depends upon a user’s ability to maintain a repeatable and realistic success rate. The DARPA team understands this, even at the prototyping phase, and that’s a good approach to designing user-centered applications in general.

We must also consider the use of immersive gaming for a greater good. According to DARPA, the source code will be made freely available for hacking come January. This means much more data and research will be conducted by people with real-world interest in prosthetic control, as well as folks interested in developing virtual technologies for other possible use cases.