In a Stanford–led research report, three participants with movement impairment controlled an onscreen cursor simply by imagining their own hand movements.
A clinical research paper led by Stanford University investigators has demonstrated that a brain–to–computer hookup can enable people with paralysis to type via direct brain control at the highest speeds and accuracy levels reported to date.

The report involved three study participants with severe limb weakness. They each had one or two baby–aspirin–sized electrode arrays placed in their brains to record signals from the motor cortex, a region controlling muscle movement. These signals were transmitted to a computer via a cable and translated by algorithms into point–and–click commands guiding a cursor to characters on an onscreen keyboard. Each participant, after minimal training, mastered the technique sufficiently to outperform the results of any previous test of brain–computer interfaces, or BCIs, for enhancing communication by people with similarly impaired movement. Notably, the study participants achieved these typing rates without the use of automatic word–completion assistance common in electronic keyboarding applications nowadays, which likely would have boosted their performance.

One participant, Dennis Degray of Menlo Park, California, was able to type 39 correct characters per minute, equivalent to about eight words per minute.

This point–and–click approach could be applied to a variety of computing devices, including smartphones and tablets, without substantial modifications, the Stanford researchers said.

“Our study’s success marks a major milestone on the road to improving quality of life for people with paralysis,” said Jaimie Henderson, MD, professor of neurosurgery, who performed two of the three device–implantation procedures at Stanford Hospital. The third took place at Massachusetts General Hospital.

Henderson and Krishna Shenoy, PhD, professor of electrical engineering, are co–senior authors of the paper, which was published online Feb. 21 in the journal eLife. The lead authors are former postdoctoral scholar Chethan Pandarinath, PhD, and postdoctoral scholar Paul Nuyujukian, MD, PhD, both of whom spent well over two years working full time on the project at Stanford.

“This study reports the highest speed and accuracy, by a factor of three, over what’s been shown before,” said Shenoy, a Howard Hughes Medical Institute investigator who’s been pursuing BCI development for 15 years and working with Henderson since 2009. “We’re approaching the speed at which you can type text on your cellphone.”

“The performance is really exciting,” said Pandarinath, who now has a joint appointment at Emory University and the Georgia Institute of Technology as an assistant professor of biomedical engineering. “We’re achieving communication rates that many people with arm and hand paralysis would find useful. That’s a critical step for making devices that could be suitable for real–world use.”

Shenoy’s lab pioneered the algorithms used to decode the complex volleys of electrical signals fired by nerve cells in the motor cortex, the brain’s command center for movement, and convert them in real time into actions ordinarily executed by spinal cord and muscles.

“These high–performing BCI algorithms’ use in human clinical trials demonstrates the potential for this class of technology to restore communication to people with paralysis,” said Nuyujukian.