What it is
Speech brain-computer interfaces today ask users to physically attempt to speak, which is tiring and slow, and they raise the question of whether private inner speech could be read out. Using multi-unit recordings from four participants, researchers found that inner (imagined, unspoken) speech is robustly represented in the motor cortex and decoded imagined sentences in real time from a vocabulary of 125,000 words. Inner and attempted speech were highly correlated, but a distinct neural motor-intent dimension separated the two.
Why it matters
Decoding imagined speech directly would let paralyzed users communicate without the fatigue of attempted articulation, a step toward effortless BCI communication. The same capability creates a genuine mental-privacy problem, since some free-form inner speech could be partially decoded during recall and counting tasks. The team addressed it head-on by demonstrating a password-gated strategy that prevents the interface from unintentionally transcribing private inner speech.
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Filed underbrain-computer interface, inner speech, neuroprosthetics, motor cortex, neural privacy