The ability to communicate using only your thoughts might sound like the stuff of science fiction. But for people who don’t have the ability to speak or move due to injury or disease, there’s great hope that this may one day be possible using brain-computer interfaces (BCIs) that can “read” relevant brain signals and translate them into written or spoken words. A research team has made a preliminary advance in this direction by showing for the first time that a computerized brain implant can decode internal speech with minimal training.

In the new NIH-supported study, researchers implanted such a device in a brain area known to be important for representing spoken words called the supramarginal gyrus in two people with tetraplegia, a condition marked by full body paralysis from the neck down due to cervical spinal cord injury. The researchers found that the device could decode several words the participants “spoke” only in their minds. While we are far from using such a device to decode whole sentences or even phrases, and the exact mechanisms of internal speech are still under study, the findings, reported in Nature Human Behavior, are notable because it had been unclear whether the brain signals involved in thinking words could be reproducibly translated.

The findings come from a team led by Richard Andersen at the California Institute of Technology, Pasadena, CA, and Sarah Wandelt, now at the Feinstein Institutes for Medical Research in Manhasset, NY, and the study was supported by the NIH Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative Research Opportunities in Humans program. Though earlier research had shown that brain implants could decode vocalized, attempted, and mimed speech, it had yet to be seen whether internal speech could be similarly decoded.