Recently, scientists unlocked the code used by neurons in the retina for sending visual data to the brain. This allowed them to create a device that restored almost-normal vision to blind mice. Now, another group of scientists has announced that they have determined the brain’s code for pronouncing vowels, and they believe that their discovery could lead to machines that speak for people who are physically unable to do so.
The research team consisted of scientists from UCLA and the Technion, Israel's Institute of Technology.
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They studied 11 UCLA epilepsy patients, who had already had electrodes implanted in their brains in order to determine where their seizures were originating. The patients’ neural activity was observed as they vocalized one of five vowels, or syllables containing those vowels.
It was found that two areas of the brain were involved, and in different ways. Neurons in the superior temporal gyrus responded to all five vowels, although at different rates of firing for each vowel. This apparently ties in with the positioning of the tongue within the mouth, which in turn allows the desired vowel sounds to be made.
By contrast, neurons in a region of the medial frontal lobe were found to each fire for only one or two specific vowels. Whereas the neurons in the temporal gyrus are generalists, the neurons in the medial frontal region are specialists. Working together, they allow us to vocalize the sounds of vowels as we think of them.
Now, the team just needs to get the encoding of the consonants figured out.
“Once we understand the neuronal code underlying speech, we can work backwards from brain-cell activity to decipher speech,” said Dr. Itzhak Fried, a UCLA professor of neurosurgery. “This suggests an exciting possibility for people who are physically unable to speak. In the future, we may be able to construct neuro-prosthetic devices or brain-machine interfaces that decode a person's neuronal firing patterns and enable the person to communicate.”