In 1997, Cathy Hutchinson suffered a brainstem stroke that left her paralyzed from the neck down. But in 2011, she was able to pick up a Thermos filled with coffee, bring it to her mouth and drink from it again.
Hutchinson, who was 58 at the time, didn’t regain control over her hands. She did it by moving a robotic arm with her thoughts.
Hutchinson controlled the robot with a technology called brain-computer interface, which uses tiny electrodes implanted in the regions of the brain that control hand and arm movements. The 96 microscopic electrodes listened to signals produced by Hutchison’s brain cells, fed them to a computer for analysis and translated them into motion, as reported in the journal Nature.
The technology was developed by the cross-disciplinary BrainGate team. Scientists from GE Global Research are working with BrainGate to better understand the electrical signals generated by the brain’s neurons.
“We’ve moved significantly closer to returning everyday functions, like serving yourself a sip of coffee, usually performed effortlessly by the arm and hand, for people who are unable to move their own limbs,” said Brown University neuroscientist John Donoghue, who leads BrainGate with his collaborators at Massachusetts General Hospital, the Department of Veterans Affairs, Stanford University, and Case Western Reserve University. “This work is a critical step toward realizing the long-term goal of creating a neurotechnology that will restore movement, control and independence to people with paralysis or limb loss.”
Donoghue’s team isn’t alone exploring the barrier between the brain and machines. “We build microelectronic brain implants that are specifically designed for nerve stimulation and recording,” says electrical engineer Craig Galligan, who designs neural implants like the one inside Hutchinson’s head at GE Global Research in New York. “We want to have the least invasive process for implanting a neural probe, and we also want to target a specific area. Part of the game is knowing exactly what neurons need to be targeted and only stimulate that area.”
Galligan and his team are now trying to understand how the brain-computer interface will evolve over the next decade. “Early on, it became clear from speaking with top neurosurgeons that the structural dimensions of the probe could have a large impact on the success of an implant,” Galligan wrote in his blog. “Narrower probes appeared to cause less tissue damage and remained functional for longer durations of implantation.”
Since scientists at the GE lab work on any number of things – from new materials for jet engines to chemical sensors based on butterfly wings and high-resolution medical scanners – Galligan reached out across the hallway to colleagues working on a technology called the MEMS Microswitch to improve on his brain probes. (GE CEO Jeff Immelt calls this idea cross-pollination the GE Store.)
The MEMs, or “micro-electro-mechanical-systems,” can be thinner than a human hair, but they also allow engineers to manage everything from battery life to medical devices and aviation systems. With the MEMs team’s help, Galligan and his colleagues were able to build and test in his lab a probe that was 2 millimeters long and 30 microns wide – less than the diameter of a human hair.
They constructed the probe from a proprietary gold alloy, which was then covered with a 4-micron parylene dielectric coating, basically a type of electrical insulation. They ablated the parylene from the tip of the probe with a UV laser to make sure that it would electrically connect only with the right brain regions. “These efforts are part of the many activities necessary before the probes are evaluated further through clinical research,” Galligan says.
Galligan says that pre-clinical trials have been encouraging. “We observed an excellent signal-to-noise ratio, which allowed for clear measurement of neural spike waveforms,” he says. He also said “the signal recording results were comparable with previously tested neural probes of larger width. These wider probes cause more tissue disruption, and thus may not remain effective for as long as our narrower prototypes.”
The team used the results to apply for an NIH grant to continue the pre-clinical work, “with our eventual longer-term goal being testing and use in humans,” Galligan says.
Galligan’s colleague Jeff Ashe has been working with Donoghue’s BrainGate team to better understand the electrical signals generated by the brain’s neurons. “We really want to know what’s happening down on the cellular level,” Ashe says. “Our sensor designs will be tiny, and they will be able to record the electrical signals coming from the individual neurons,” Ashe says. “Being able to record and separate the signals from the individual neurons, we can then interpret the information the neurons are creating and the functions their circuits should be producing.”
One day, these implants could help treat brain disease. Says Ashe: “We are looking at tools that actually can listen to the brain cells, understand their language, and speak back to the brain.” Ashe says. “The Brain can communicate to devices, and devices will communicate to the brain.”