Japanese scientists have developed a device which allows people with severe paralysis to communicate.
The headband - called kokoro-gatari - has been developed to help patients incapable of even the slightest movement, such as blinking.
It works by measuring the one function these patients can still control - blood flow through their brains.
In tests it enabled patients to signal yes or no to a question with an 80% accuracy.
You may think the accuracy rate is 20% less than perfect but it is a big leap from zero for us
The device, whose name translates to mind-talk in English, was developed by electronics giant Hitachi.
It has been designed to aid people with a form of motor neurone disease called Amyotrophic Lateral Sclerosis.
The condition ultimately affects all voluntary muscles, making patients incapable of even the slightest movements - but their ability to think is unaffected.
If the patient wants to agree with a question they try to activate the blood flow to the frontal lobe of the brain.
They do this by working out mental arithmetic or trying to remember the words of a song.
If they want to disagree they just relax to try to keep the blood flow unchanged.
The headband, which emits near-infrared rays to measure the flow of blood, takes just over half a minute to interpret the answer.
At one point the design project was halted because the developers could not get 100% accuracy.
But advocates for disabled people persuaded them that less than perfect communication was better than no communication at all.
Kensuke Yanagita, of the Japanese ALS Association, said: "Caregivers are always wondering if what they have done is okay to patients as there is no way to confirm it.
"You may think the accuracy rate is 20% less than perfect but it is a big leap from zero for us. At least caregivers would be able to know the patient is feeling good or not."
The developers hope to market the device in Japan before the end of the year.
However, it will not come cheap at more than £2,000.
Tricia Holmes, of the UK MND Association, said: "We warmly welcome any advances in communication aid technology that enable people with MND to live as full a life as possible.
"Although people with MND often lose the use of their limbs and speech, the mind generally remains unaffected.
"So the 'mind-talk' device represents an important and exciting breakthrough for people who cannot currently communicate their wishes."