California, June 15 -- A man with a severe speech disability can speak expressively and sing using a brain implant that translates his neural activity into words almost instantly. The device conveys changes of tone when he asks questions, emphasizes the words of his choice, and allows him to hum a string of notes in three pitches.

The system, known as a brain-computer interface (BCI), used artificial intelligence (AI) to decode the participant's electrical brain activity as he attempted to speak. The device is the first to reproduce not only a person's intended words but also features of natural speech such as tone, pitch, and emphasis, which help to express meaning and emotion.

In a study, a synthetic voice that mimicked the participan...