Scientists have developed a 3D 'brain dictionary' that may help make out our inner thoughts and give voice to people who cannot speak, such as those who have had a stroke, brain damage or motor neuron diseases. Researchers built a "semantic atlas" that shows in glowing colours and multiple dimensions how the human brain organises language.

The atlas identifies brain areas that respond to words that have similar meanings. The thesaurus-like map could eventually help give voice to those who cannot speak, such as people who have had a stroke, brain damage or motor neuron diseases such as ALS, researchers said. The study found that different people share similar language maps.

"The similarity in semantic topography across different subjects is really surprising," said study lead author Alex Huth, from the University of California, Berkeley. While mind-reading technology remains far off on the horizon, charting language organisation in the brain brings decoding inner dialogue a step closer, researchers said.

"This discovery gravel the way for brain-machine interfaces that can construe the meaning of what people want to express," Huth said. "Imagine a brain-machine interface that doesn't just figure out what sounds you want to make, but what you want to say," he said. For example, clinicians could track the brain activity of patients who have difficulty communicating and then match that data to semantic language maps to determine what their patients are trying to express.