The horrifying condition in which mentally alert patients become completely paralysed was made famous by JeanDominique Bauby's book The Diving-Bell and the Butterfly, which he dictated, letter by letter, by moving one of his eyelids.

This "locked in" condition, which can be caused by a stroke or neurological disease, can sometimes leave patients completely unable to communicate.

Researchers at the University of Tubingen in Germany and elsewhere have designed a communications system for these patients using a device called an "electroencephalogram", which monitors an individual's brainwaves.

With practice, patients can learn to drive cursors on a video screen, allowing them to select letters of the alphabet, according to a letter published yesterday in the journal Nature.

University of Tubingen, Germany, email neils.birbaumer@uni-tuebingen.de