With minimal training, people can communicate silently through a functional magnetic resonance imaging (fMRI) machine by performing mental-imagery tasks that correspond to the 26 letters of the English alphabet.

Bettina Sorger at Maastricht University in the Netherlands and her team asked six healthy volunteers to use a set of three mental tasks. Each task could be performed for three different durations and its onset delayed by three different lengths of time. This generated 27 different fMRI activation patterns, one for each letter and one for a space. In a one-hour fMRI scanning session, the volunteers spelled out their answers to open questions (examples pictured) by carrying out these mental tasks, with the help of a visual letter-encoding guide. A decoding algorithm translated the fMRI signals back into letters (pictured, top three rows) in real-time.

The technique could be used by patients who cannot communicate physically but are still conscious.

Credit: ELSEVIER

Curr. Biol. http://dx.doi.org/10.1016/j.cub.2012.05.022 (2012)