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The newer, brain-controlled versions of these devices work in one of two ways; either through an electroencephalogram (EEG) cap that detects neural activity using electrodes placed on the scalp or a device planted directly into the brain. A decoder translates these neural signals into commands that move computer cursors and prosthetic limbs. BrainGate has developed a device, named after itself, which is composed of an “aspirin-sized array of electrodes” that is implanted in the motor cortex, the area of the brain primarily responsible for voluntary movement. Patients use their thoughts to move a cursor to virtually type on a screen. Researchers are continually working to improve the speed of these systems. In a study published this September in Nature Medicine the group used the BrainGate system, to achieve the highest published performance of “virtual typing” by a person to date—which translated to approximately six words per minute, still much slower than the average typing speed. (Scientific American is part of Nature Publishing Group.)

A major limitation of these devices is that the decoder requires frequent calibration—which is needed to accurately estimate an individual’s movement intention—because neural signals change over time. This could be caused by a slight movement of the electrode or outside noises, such a phone ringing or an ambulance driving by. Hochberg and his team reported in a study published this week in Science Translational Medicine that they have overcome this obstacle by creating an automatically calibrating device. “A lot of the concerns [around BCIs] had to do with the stability of the recordings, because if the decoder is calibrated to one time point, there is a natural limit of how long the decoder could be good for, ” says Beata Jarosiewicz, neuroscientist at Brown and lead author of the paper. With the new and improved system, patients were able to type for several hours at a time across multiple days without the need for intervening technicians—a big step in improving usability. “Lack of [stability in the neural recordings] has been a persistent problem with BCIs, and the investigators used a set of well-considered approaches to effectively address this for cursor control, ” says Andrew Schwartz, a University of Pittsburgh neuroscientist who has done extensive work on brain-controlled devices but was not involved in the study. “Furthermore, the same basic ideas can probably be applied to more elaborate control, for instance, of an arm and hand, ” he adds.