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Unique Speech Fluctuations in Humans

Unique Speech Fluctuations in Humans

Valley girls use it to create a unique way of speaking; those speaking Mandarin Chinese use it to create different words with the same pronunciation, and we all use it to turn a statement into a question or to put emphasis on different parts of a sentence.

We’re talking about pitch: that ability of the vocal cords to change the frequency of a person’s by tightening or loosening the vocal cords. Up until now, experts weren’t really quite sure exactly how spontaneous pitch control was achieved in humans.

Spontaneous Pitch Control

In fact, humans are the only primates that can control pitch on command. Spontaneous pitch control is essential to the way we communicate. Without out it, much of the meaning we convey with the use of intonation in verbal discourse would be lost. It would be more like the communication we experience when we email or text.

New Research

Thanks to research conducted by scientists at UC San Francisco, the areas the human brain uses to control pitch has been revealed. A study conducted by Benjamin Dichter, PhD a postdoctoral researcher and Edward F. Chang, MD professor of neurological surgery found that one specific part of the brain, the dorsal laryngeal motor cortex, was primarily responsible for quick changes in pitch.

In the study participants were asked to read the sentence, “I never said she stole my money,” with emphasis on different parts of the sentence. While participants said the sentence over and over, researchers studied the activity in the dorsal laryngeal motor cortex. They found this area of the brain was very active when pitch level was increased.

Implications For Hearing

Much of hearing and processing someone’s meaning is up to how the message is received. If someone is able to hear every intonation conveyed, they are more likely to perceive the speaker’s intent correctly. However, when intonation is absent, or not perceived, the opportunity for error widens.

Now that researchers have pinpointed the exact areas of the brain that control pitch that’s so crucial to interpersonal communication, research can begin on developing technologies to tap into those areas and control pitch with a prosthesis.  

People who may have experienced damage to key areas of the brain, at some point in the future, may have access to ways to recover this important part of human communication.

Implications For Automated Speaking

For those individuals with the inability to speak, a speech prosthetic would enable users to place emphasis automatically by just thinking about intonation.

The study found that the dorsal laryngeal motor cortex will respond to pitch automatically. In the study, patients who heard their own voices played back to them, experienced activation in the dorsal laryngeal motor cortex.

In pre-operation settings, researchers found that stimulating this area of the brain caused automated responses in the larynx and sometimes even automatic voicing. While more research needs to be done, the identification of this crucial area for laryngeal activation in speech voicing is an important step in giving those who have experienced a loss of their ability to communicate new hope.

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