For America's approximately 5,000 people who suffer cervical spinal cord injuries each year, typically resulting in quadriplegia, new brain-computer interfaces are not merely fun and games, they're a means to perhaps someday live a full life again and possibly regain some movement. Standing in the way is the complexity of the in-tissue implants needed to gain more complex control.
A newly designed implant from the California Institute of Technology (Caltech) aims to simplify the process of attaching miniature electrodes to brain neurons via robotic control using MEMS devices, tiny little motors. The Caltech Robotics Burdick group is running the project. The group is led by research engineers Michael Wolf, Joel Burdick, his mentor, Jorge Cham and Edward Branchaud. According to researchers, this is the "first robotic approach to establishing an interface between computers and the brain by positioning electrodes in neural tissue".
The research "could enhance the performance and longevity of emerging neural prosthetics, which allow paralyzed people to operate computers and robots with their minds" according to the researchers. An early prototype of the system has been constructed.
The prototype is currently undergoing testing on non-human primates. According to the researchers, the device "is designed to fit inside a standard laboratory cranial chamber, used for acute experiments in non-human primates, to allow semi-chronic operation. A semi-chronic design has the advantage that the device can be repositioned over a different region with minimal effort and without need for additional surgeries."
The device positions four electrodes to optimize action potentials. Wolf describes the overall design of the device, stating, "Our approach consists of implanting a small robotic device (and accompanying control algorithm) with many individually-motorized electrodes that each autonomously locate, isolate, and track a neuron for long periods of time. To further complicate matters, we wish to find signals only from neurons dedicated ('tuned') to a particular task, say controlling an 'arm reach.' While the primary aim of such technology is for a neural interface for neuroprostheses, such a device may also advance the state-of-the-art experimental techniques for electrophysiology."
While the Caltech team is still working on fine tuning the MEMS design for the final version of the device, the software algorithm is complete. The algorithm in many respects is the keystone of the project. It was actually adapted from algorithms the U.S. military uses to track airplanes. On a most basic level, the algorithm involves the motors slowly being powered to drive the probe down into a tissue. As it picks up a signal it pushes the probe deeper until the signal deepens, in which case it backs up to position itself on the active neuron.
Neuroprosthetics, the science of using brain implants to power robotic limb movement, is a budding field of science, buoyed by recent better understanding of the human brain and new nanoelectronic designs. However longevity is a major concern as cells in the brain can shift slightly and even slight shifts in an in-brain electrode probe could disconnect it.
The advance of medical science is frustratingly slow for the afflicted, but with improvements such as the new Caltech interface, quadriplegics and those suffering from other neurological conditions may someday be able to walk and lead mostly normal lives.