Researchers at Maastricht University in The Netherlands have developed a device that gives a voice to those who are completely unable to speak or move at all. Building on previous work using functional magnetic imaging (fMRI) technology, which allowed individuals to give yes/no responses or answer multiple-choice questions, the new approach allows for full, unscripted back-and-forth conversations.

FMRI is a non-invasive technique that measures brain activity by detecting the changes in blood oxygenation and flow that occur in response to neural activity. It has previously been used to assess consciousness in people described as being in an unconscious, vegetative state and enable them to answer yes/no questions. This was then expanded to allow individuals to answer the equivalent of multiple-choice questions having four or fewer possible answers.

Maastricht University’s Bettina Sorger and colleagues have now taken this approach one step further by creating a real-time, brain-scanning speller. Sorger’s team came up with a letter-encoding technique in which participants were asked to perform a particular mental task for a set period of time to signify a specific character. This produced 27 distinct brain patterns corresponding to each letter of the alphabet and a space character.

The letter-encoding technique required almost no pre-training and the 27 distinct brain patterns could be automatically decoded in real time. Communication experiments carried out by the team saw participants holding a mini-conversation consisting of two open ended questions and answers. Every participant tested was able to successfully produce answers within a single one-hour session.

Because MRi machines are bulky and expensive pieces of equipment, Sorger hopes the fMRI technology she and her team have developed can be transferred to a more portable and affordable method of measuring blood flow, such as functional near-infrared spectroscopy (fNIRS).

The team’s research is detailed in a report published online in Current Biology.