Key points from article :
A new breakthrough in brain-computer interfaces (BCIs) has taken a major step forward by enabling people to communicate using only their thoughts, without the need to physically attempt speech. Reported in Cell and led by Erin Kunz, a postdoctoral researcher at Stanford University, the study tested a neural prosthetic system designed for people with conditions such as amyotrophic lateral sclerosis (ALS) or brain stem stroke. Unlike earlier speech-decoding BCIs, which required users to make the effort of inhaling or mimicking speech, this new “inner speech” device works by decoding imagined speech directly from brain activity.
The system uses electrodes implanted in the motor cortex—the part of the brain that controls movements of the vocal tract—and feeds neural signals into machine learning models. While earlier versions could only decode a small vocabulary, this new system allowed participants to access a dictionary of 125,000 words and produce text at conversational speeds of 120–150 words per minute, rivaling natural speech. For participants who previously struggled with slow, effortful devices, this represented a dramatic improvement, making communication smoother and more natural.
Importantly, the technology works only if a person can still mentally form a speech plan, even if their muscles cannot execute it—a condition known as dysarthria. To safeguard privacy, the researchers included a code phrase, “chitty chitty bang bang,” which let participants control when the device would start or stop transcribing their inner speech. This ensures that everyday thoughts remain private, addressing concerns about mental privacy and ethical use of brain-reading devices.
For Kunz, the work is also deeply personal: her late father had ALS and lost his ability to speak, motivating her to pursue this field. She emphasizes the extraordinary contributions of the study’s participants, who volunteered not just for their own benefit but to advance communication technologies for future patients with paralysis. Their involvement, she notes, highlights both the promise of BCIs and the human generosity that makes such medical progress possible.
