Changes in vocal pitch, part of what linguists call ‘speech prosody’, are almost as fundamental to human communication as melody is to music.
In tonal languages such as Mandarin Chinese, pitch changes can completely alter a word’s meaning
But even in a non-tonal language like English, differences in pitch can significantly change the meaning of a spoken sentence.
The brain’s ability to interpret these changes in tone on the fly is remarkable given that each speaker has their own typical vocal pitch and style – some have low voices and others high.
The brain must track and interpret these pitch changes while simultaneously parsing which consonants and vowels are being uttered, what words they form, and how they combine into phrases and sentences – within a millisecond.
Researchers from the University of California, San Francisco, found the brain cells responsible by studying ten patients suffering from epilepsy in 2017.
These cells are located in a small area known as the superior temporal gyrus (STG).
As the pitch of the sentence goes high, neural activity increased.
What this research showed is that there are specific regions and select cells which can detect differences in pitch.
Some neurons distinguish between sounds speakers based on differences in their average vocal pitch range.
As well as pitch, the human brain also has different regions which help determine between sounds.
Some neurons pick up fundamental differences in sounds of words – for example, ‘reindeer’ sounds different from ‘lawyers’ no matter who is talking.
Yet another group of neurons distinguish between different intonation patterns.
This animation highlights pitch-sensing cells in a small brain area known as the superior temporal gyrus (STG). As the pitch of the sentence goes high (red), neural activity in certain areas increased (credit: Carla Schaffer / AAAS)