Using electrode implants, deep-brain-stimulation therapies can zap neurons with tiny electrical pulses to treat Parkinson's, depression, and epilepsy. Cochlear implants restore hearing to the deaf, while artificial retinas can partially restore sight to the blind. Thought-controlled robotic limbs have already enabled quadriplegics to feed themselves and reach out to touch a loved one, and may one day help people with paralysis to live independently.
Yet technologies that interface between neurons and computers are still in their infancy. Here are four big improvements that will soon bring brain-machine interfacing to the next level.
Better Materials, Longer Lifetimes
Today's brain implants last for only one to two years in primates. After a while, the electrodes simply stop communicating with the neurons and scientists aren't sure why. One theory is that the electrodes (essentially stiff beds of needles) damage surrounding cells and capillaries, causing scar tissue to form around the electrode. Several research groups are working to create electrodes that are more flexible and biocompatible. "Think of lenses," Michel Maharbiz, an electrical engineer at University of California, Berkeley, said during a talk on Saturday.
Maharbiz says his group envisions an ultrathin, pliable implant that sits on top of the brain and dangles strips of flexible electrodes down into the brain tissue, "so you have almost a thin spaghetti permeating the brain and taking data." By integrating more naturally with the brain, such biocompatible electrode arrays should increase the lifetime of the devices.
Sensory Feedback and Better Control
Current brain-controlled prosthetic limbs don't provide sensory feedback to the user. A patient using a prosthetic limb can't feel the cup she's grabbing—she has to watch the limb to keep track of where it is in relation to the rest of her body. "Sensation is one of the missing elements in the BMI [brain-machine-interface] field," said Jose Carmena, who also studies neuroprosthetics at UC, Berkeley. He and other scientists are trying to find out how to use prosthetic limbs to collect sensory information—such as texture or temperature—and translate that information into electrical signals the brain can interpret. Integrating sensory feedback not only will provide a richer experience for the user, but can also help patients use the prosthetics to perform finer and more complex movements such as tying their shoes or brushing their teeth.
Today's BMI implants must be tethered to an outside energy source to send and receive electrical signals. That means wires coming out of a hole in the patient's skull, leaving an easy route for infection to enter the brain. That leaves the patient vulnerable and also limits what the brain-controlled prosthetic can do.
During Saturday's talk, Carmena and Maharbiz revealed their newest concept for an untethered BMI. The idea, which they've named Neural Dust, involves replacing needle electrodes with a sprinkling of tiny ultrasound transceivers throughout the brain. The free-floating nodes are meant to be smaller than the width of a human hair. They could simultaneously interface with thousands of neurons from various parts of the brain and wouldn't need batteries or wires. Instead, they'd be powered similarly to RFID tags, which couple with an outside energy source to transmit data. Although the group hasn't built a prototype yet, Carmena and Maharbiz think they'll be testing Neural Dust in animal models within a year and a half.
New Uses for BMI
BMIs could have many uses that haven't even been explored yet. For example, biomedical engineer Theodore Berger from the University of Southern California has created an implantable chip that can recover lost memory function in rats and primates.
To test the chip in rats, Berger's group placed individual rats in a cage with two levers. After pressing one lever, the rat had to remember to press the opposite lever after being distracted for a short time. By recording neural activity in the rat's hippocampus as it chose the correct lever, the scientists were able to pick up on firing patterns that corresponded to each lever. When the researchers impaired a rat's hippocampus—the area of the brain that turns short-term memories into long-term memories—it had a harder time remembering which lever it had just pushed. By hooking the rats up to an artificial hippocampus and replaying the correct neural firing patterns, the rats remembered.
Berger thinks the method could be applied in humans to repair cognitive deficits from stroke, aging, head trauma, and even epilepsy. Moreover, the group even used the implants to strengthen memory in rats whose hippocampi were intact—potentially pointing to cognitive enhancements for humans in the decades to come.
As BMI technology advances, it'll open up even more avenues. At the conference on Sunday, Berger hinted that his group is thinking ahead to a new generation of enhancements. "This project is to develop a neural prosthesis for cognition—first for memory, but later for other types of cognitive functions," he said.