image: Researchers have identified neurons in the brain that help discern changes in relative pitch, playing an essential role in helping humans extract meaning from speech. This material relates to a paper that appeared in the Aug. 25, 2017, issue of Science, published by AAAS. The paper, by C. Tang at University of California, San Francisco in San Francisco, Calif., and colleagues was titled, "Intonational speech prosody encoding in the human auditory cortex." view more
Credit: Carla Schaffer / AAAS
The ability for humans to discern changes in pitch as they listen to a speaker is essential for extracting meaning from words, and now researchers have identified a set of neurons responsible for detecting such relative changes in pitch. Pitch is so important to human language that the exact same words can have different meaning if the pitch is different. For example, "Anna likes oranges" can be a statement, or if the pitch varies near the end, the phrase can be posed as a question, "Anna likes oranges?" Humans are so good at discerning pitch that they can even recognize musical melodies when the notes are transposed. Now, Claire Tang and colleagues report a subset of neurons responsible for discerning relative pitch. They studied the neural activity of ten patients suffering from seizures, who had implants monitoring their brain activity. They exposed the patients to synthesized voices that independently varied in intonation contour, phonetic content, and speaker identity (male versus female). The data reveal brain regions that responded the same way to completely different sentences that were presented with the exact same pitch pattern. As well, there were distinct neural responses for males and females, who tend to have absolute differences in pitch. The researchers then exposed the participants to sentences spoken by hundreds of male and female speakers, detecting areas of the brain that were tuned to high relative pitch and low pitch, respectively. In total, 38 of 45 of electrodes recording intonation were better predicted by relative pitch than absolute, the authors report.
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Journal
Science