Two paralysed patients with motor neurone disease (MND) have controlled a cursor on a computer screen by imagining themselves wiggling their fingers.
One was also able to "type" words using the cursor at a rate of six a minute.
Each had an electrical brain implant that picked up nerve signals corresponding to the finger movement and relayed them to the computer.
Similar experiments have been conducted on monkeys but never so successfully with humans before.
Computer software was used to translate the neural signals into two dimensional movement commands.
Both participants demonstrated a high level of speed and precision as they completed tests that involved moving a white dot around on a screen.
The pair showed faster and more precise neural cursor control than that obtained in a previous study, the scientists reported in the journal Nature Medicine.
Both were tetraplegic patients who had lost the use of all four limbs.
One demonstrated a real-world application of the technology using a system that employs simple cursor movements to generate words.
The participant, described only as "T6", was able to type 115 words in 19 minutes, a rate of around six words a minute.
The scientists, led by Dr Jaimie Henderson, from Stanford University in the US, wrote: "Continued translation of neural prosthetic system studies from animal models to clinical research is vital both for advancing system performance and for understanding real-world challenges.
"The incorporation of advanced, high-performance system design innovations, informed and iterated through clinical research, may bring neural prostheses closer to clinical utility for people with motor impairments."