Science journalist Tibi Puiu reports on a new technique that enabled a woman to speak by using her thoughts to control a voice synthesizer:

In a California hospital, a woman who hadn’t spoken in nearly two decades silently mouthed the words, “Why did he tell you?” Moments later, a synthetic voice — trained on a single clip recorded before a stroke robbed her of speech — spoke them aloud.

The words weren’t typed or selected from a menu. They came directly from her brain.

Researchers at the University of California, San Francisco, have unveiled a brain implant that translates thoughts into speech at near-conversational speed. The developments mark a turning point for brain–computer interfaces, or BCIs — technologies that decode neural signals to help people communicate. 

“A Brain Implant Just Turned a Woman’s Thoughts Into Speech in Near Real Time,” ZME Science, April 1, 2025

A brainstem stroke had robbed her of her ability to speak in 2005. Researchers enabled her thoughts to control the speech synthesizer directly via an implant placed on her cerebral cortex. The synthesizer’s speech was modeled on her wedding video from the days when she could still speak, so the voice would sound like hers.

Puiu notes that the key benefit of the new system is that it is much faster than traditional methods, cutting the time from internal speech to audible speech to less than three seconds:

It’s early days yet, of course. The demonstration is more a proof of concept than anything else but it is an exciting development.

From the paper:

Natural spoken communication happens instantaneously. Speech delays longer than a few seconds can disrupt the natural flow of conversation. This makes it difficult for individuals with paralysis to participate in meaningful dialogue, potentially leading to feelings of isolation and frustration. Here we used high-density surface recordings of the speech sensorimotor cortex in a clinical trial participant with severe paralysis and anarthria to drive a continuously streaming naturalistic speech synthesizer. 

Littlejohn, K.T., Cho, C.J., Liu, J.R. et al. A streaming brain-to-voice neuroprosthesis to restore naturalistic communication. Nat Neurosci (2025).

Cross-posted at Mind Matters News.