The technique suggested in the patent is entirely non-invasive. It describes a device that fires pulses of ultrasound at the head to modify firing patterns in targeted parts of the brain, creating "sensory experiences" ranging from moving images to tastes and sounds. This could give blind or deaf people the chance to see or hear, the patent claims.

While brain implants are becoming increasingly sophisticated, the only non-invasive ways of manipulating the brain remain crude. A technique known as transcranial magnetic stimulation can activate nerves by using rapidly changing magnetic fields to induce currents in brain tissue. However, magnetic fields cannot be finely focused on small groups of brain cells, whereas ultrasound could be.

The application contains references to two scientific papers presenting research that could underpin the device. One, in an echo of Galvani's classic 18th-century experiments on frogs' legs that proved electricity can trigger nerve impulses, showed that certain kinds of ultrasound pulses can affect the excitability of nerves from a frog's leg.

If the method described really does work, in addition to possibly evoking sensory experiences, it could have all sorts of uses in research and medicine. Independent experts are not dismissing the idea out of hand. "I looked at it and found it plausible," says Niels Birbaumer, a pioneering neuroscientist at the University of Tübingen in Germany who has created devices that let people control devices via brain waves.

Excerpt from New Scientist, 4/2005