• Posted August 15, 2025

New Brain Implant Could Let People Speak Just by Thinking Words

For the first time, scientists have created a brain implant that can “hear” and vocalize words a person is only imagining in their head.

The device, developed at Stanford University in California, could help people with severe paralysis communicate more easily, even if they can’t move their mouth to try to speak.

“This is the first time we’ve managed to understand what brain activity looks like when you just think about speaking,” Erin Kunz, lead author of the study, published Aug. 14 in the journal Cell, told the Financial Times.

“For people with severe speech and motor impairments, brain-computer interfaces [BCIs] capable of decoding inner speech could help them communicate much more easily and more naturally,” said Kunz, a postdoctoral scholar in neurosurgery.

Four people with paralysis from amyotrophic lateral sclerosis (ALS) or brainstem stroke volunteered for the study. One participant could only communicate by moving his eyes up and down for “yes” and side to side for “no.”

Electrode arrays from the BrainGate brain-computer interface (BCI) were implanted in the brain area that controls speech, called the motor cortex. 

Participants were then asked to try speaking or to silently imagine certain words.

The device picked up brain activity linked to phonemes, the small units that make up speech patterns, and artificial intelligence (AI) software stitched them into sentences.

Imagined speech signals were weaker than attempted speech but still accurate enough to reach up to 74% recognition in real time, the research shows.

Senior author Frank Willett, an assistant professor of neurosurgery at Stanford, told the Financial Times the results show that “future systems could restore fluent, rapid and comfortable speech via inner speech alone,” with better implants and decoding software.

“For people with paralysis attempting to speak can be slow and fatiguing and, if the paralysis is partial, it can produce distracting sounds and breath control difficulties,” Willett said. 

The team also addressed privacy concerns. In one surprising finding, the BCI sometimes picked up words participants weren’t told to imagine — such as numbers they were silently counting.

To protect privacy, researchers created a “password” system that blocks the device from decoding unless the user unlocks it. In the study, imagining the phrase “chitty chitty bang bang” worked 98% of the time to prevent unintended decoding.

“This work gives real hope that speech BCIs can one day restore communication that is as fluent, natural and comfortable as conversational speech,” Willett said.

More information

Learn more about the technology by reading the full study in the journal Cell.

SOURCE: Financial Times, Aug. 14, 2025