A new brain scanner has been developed to help people who are completely paralysed speak by enabling them to spell words using their thoughts.
It uses functional magnetic resonance imaging (fMRI) to help patients choose between 27 characters - the alphabet and a blank space.
Each character produces a different pattern of blood flow in the brain, and the device interprets these patterns.
The British Neurological Association called the research "exciting".
The study appears in Current Biology journal of Cell Press.
fMRI is normally used to track brain activity by measuring blood flow.