Scientists have now identified the part of the brain which governs the "music" of speech and is responsible for controlling the voice pitch.

The findings suggested that activation of neurons in one brain area, called the dorsal laryngeal motor cortex, was linked with quick changes in pitch, such as when different words are emphasized in a sentence. The more active that area of the cortex was, the higher the speaker's pitch on individual words would be, both during speech and when the subjects were singing a simple melody.

"Understanding how we speak goes far beyond just knowing where speech functions are localized in the brain. Even more important is to understand how brain cells actually encode the command signals for the muscles of the mouth and throat that make speech possible," said Edward F. Chang from the University of California.

In the study, published in the journal Cell, the team showed how the brains of some of the epilepsy patients who volunteered for the study modulated changes in pitch to emphasize different words in the sentence "I never said she stole my money", using a method known as electrocorticography or ECoG -- brain monitoring using electrodes.

The participants read the sentence multiple times, emphasising a different word each time, which changed the meaning of the sentence. This made it possible for the researchers to look at differences in brain activity due to how speakers emphasised different words in the sentence by changing pitch, without changing the words being spoken.

Further, while the patients were undergoing brain-mapping in preparation for neurosurgery, the researchers electrically stimulated neurons in the dorsal laryngeal motor cortex. They found that stimulating those neurons not only caused the larynx -- known as voice box which is involved in producing sounds -- muscles to flex, but also caused some patients to spontaneously vocalize.

Interestingly, the researchers found that dorsal laryngeal motor cortex also responds to pitch when the patients silently listened to their own speech played back. The study would pave way for advanced brain prosthetics that can lend nuanced, naturalistic voices to those unable to speak, researchers said.