August 22, 2012
Code In Brain Key To Pronouncing Vowels, Could Help Speech Paralysis
Connie K. Ho for redOrbit.com — Your Universe Online
Loss of muscle functioning in the body. Difficulty transferring message from the brain to muscles. These are just a few traits of paralysis that scientists examined in terms of its relationship to speech. A recent study by University of California, Los Angeles (UCLA) and Technion, Israel's Institute of Technology, researchers revealed a code in the brain that helps pronounce vowels.According to the researchers, human speech sounds are based on coordinated movement of structures near the vocal tract. The researchers were able to break down the code in brain cells that helps individuals in speech and pronunciation. They believe that this discovery could help scientists restore speech for those who suffer paralysis due to injury or disease.
"We know that brain cells fire in a predictable way before we move our bodies," noted Dr. Itzhak Fried, a professor of neurosurgery at the David Geffen School of Medicine at UCLA, in a prepared statement. "We hypothesized that neurons would also react differently when we pronounce specific sounds. If so, we may one day be able to decode these unique patterns of activity in the brain and translate them into speech."
In the project, the investigators followed 11 UCLA epilepsy patients that had electrodes implanted in their brains to record the origin of their seizures. The researchers were able to track the neuron activity when the patients spoke one of five vowels or any syllables that contained vowels. With the help of Technion, the UCLA team examined the process the neurons underwent to encode vowel articulation at the single-cell and collective level.
Furthermore, the findings were recently published in Nature Communications, a multidisciplinary journal focused on research in the biological, chemical, and physical sciences. The scientists discovered that there were two areas that kept neurons associated to speech and attuned to vowels. The superior temporal gyrus and a part of the medial frontal lobe allowed encoding to happen, but happened in different ways. In particular, the neurons in the superior temporal gyrus reacted to all the vowels but performed with different rates of firing. On the other hand, the medial front region contained neurons that fired only when a specific vowel was spoken.
"Single neuron activity in the medial frontal lobe corresponded to the encoding of specific vowels," explained Fried in the statement. "The neuron would fire only when a particular vowel was spoken, but not other vowels."
The researchers concluded that, at the collective level, the neurons´ encoding of vowel in the superior temporal gyrus showed that tongue´s position inside the mouth made speech possible.
"Once we understand the neuronal code underlying speech, we can work backwards from brain-cell activity to decipher speech," commented Fried in the statement. "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."
The Dana Foundation, the European Council, Lady David, L. and L. Richmond research funds, and the National Institute of Neurological Disorders and Stroke provided funding for the study.