However if all eye movements are lost, as in the case of patients in the study, the condition is referred to as complete locked-in syndrome. Most doctors believed it was impossible for people who were effectively trapped inside themselves to contact the world outside.

But the new device was able to pick up the changes happening beneath the services, and read thoughts.

All four patients in the study were suffering from ALS - a progressive motor neuron disease that leads to complete destruction of the part of the nervous system responsible for movement.

They were wired up to a non-invasive brain-computer interface (BCI) which detected responses by measuring changes in blood oxygen levels in the brain.

To calibrate the programme, scientists asked questions which they already knew the answer to, such as ‘You husband’s name is Joachim?’

One of the patients Kerstin Wirth, 26, of Leverkusen in Germany, was diagnosed with juvenile ALS (Lou Gehrig's disease) and within just four years was in a completely locked-in state.

But using the new technology she was able to confirm that her mother's name was Margit and say that the still felt happy with her life.