Other methods of interfacing with the brain via electrodes include those put on the scalp for electroencephalography (EEG) and ones placed under the skull on the brain’s surface, known as electrocorticography (ECo G).
The advantage of intracortical implants is they can pick out activity from single cells whereas the other methods capture the average activity of thousands of neurons.
“This is the fastest typing anyone has shown with a BCI,” says biomedical engineer Jennifer Collinger, of the University of Pittsburgh, who was not involved in the study.
“It's on par with technologies like eye-trackers, but there are groups those technologies don’t work for such as people who are “locked-in.” These speeds also approach what ALS patients questioned in a survey said they would want from a BCI device.
For typing, however, one important barrier has been reaching speeds sufficient to justify adopting the technology, which usually involves surgery.
A study published Tuesday in reports the results of a system that enabled three participants—Degray and two people with amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease, a neurodegenerative disease that causes progressive paralysis)—to type at the fastest speeds yet achieved using a BCI—speeds that bring the technology within reach of being practically useful.
“We need to establish measures so that—in spite of potential variability between people, methods and researchers—we can really say, ‘clearly this new advance led to higher performance,’ because we have systematic ways of comparing that,” says co-lead author Chethan Pandarinath, then a postdoctoral fellow at Stanford.
The neural signals recorded by the electrodes are transmitted via a cable to a computer where algorithms developed in Shenoy's lab decode the participant's intentions and translate the signals into movements of a computer cursor.
The Stanford team is part of a multi-institute consortium called Brain Gate, which includes Massachusetts General Hospital and Brown University, among others.
“You're getting to the point where performance is good enough that users would actually want to have it,” Collinger says.
Participants had either one or two tiny (one-sixth-inch) electrode arrays implanted on the surfaces of their brains.
A participant enrolled by Stanford University in the Brain Gate clinical trial uses the brain-computer interface to type by controlling a computer cursor with her thoughts.