After a long research on our words pronunciations
Scientists at UCLA and the Technion, Israel's Institute of Technology, have
unraveled how our brain cells encode the pronunciation of individual vowels in
speech. Published in the Aug. 21 edition of Nature Communications, the
discovery could lead to new technology that verbalizes the unspoken words of
people paralyzed by injury or disease.
"We know that brain cells fire in a predictable way
before we move our bodies," explained Dr. Itzhak Fried, a professor of
neurosurgery at the David Geffen School of Medicine at UCLA. "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."
Fried and Technion's Ariel Tankus, formerly a
postdoctoral researcher in Fried's lab, followed 11 UCLA epilepsy patients who
had electrodes implanted in their brains to pinpoint the origin of their
seizures. The researchers recorded neuron activity as the patients uttered one
of five vowels or syllables containing the vowels.
With Technion's Shy Shoham, the team studied how the
neurons encoded vowel articulation at both the single-cell and collective
level. The scientists found two areas -- the superior temporal gyrus and a
region in the medial frontal lobe -- that housed neurons related to speech and
attuned to vowels. The encoding in these sites, however, unfolded very
differently.
Neurons in the superior temporal gyrus responded to all
vowels, although at different rates of firing. In contrast, neurons that fired
exclusively for only one or two vowels were located in the medial frontal
region.
"Single neuron activity in the medial frontal lobe
corresponded to the encoding of specific vowels," said Fried. "The
neuron would fire only when a particular vowel was spoken, but not other
vowels."
At the collective level, neurons' encoding of vowels in
the superior temporal gyrus reflected the anatomy that made speech
possible-specifically, the tongue's position inside the mouth.
"Once we understand the neuronal code underlying
speech, we can work backwards from brain-cell activity to decipher
speech," said Fried. "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 study was supported by grants from the European
Council, the National Institute of Neurological Disorders and Stroke, the Dana
Foundation, Lady David and L. and L. Richmond research funds.
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