Scientists Locate Speech Forming Part of the Brain

Researchers have discovered the part of the brain that is sensitive to timing and plays an important role in human language.

In order to under what other people are saying, the brain needs to interpret different time signatures making timing an important part of human speech.  Speech is generally made of different time measurements.

It has been known that some measurements are phonemes that are the shortest unit of speech and last only between 30 and 60 milliseconds.  Syllable is the other measurement and lasts between 200 and 300 milliseconds while entire words are even longer. In order to deal with the information send by speech, the auditory system will sample the information in chunks that are equivalent to the average consonant or syllable.  Researchers referred to these chunks as "speech quilts," and they found that the shorter the quilt, the more disruptive they were to the speech's structure.

For the new groundbreaking study, researchers tried to the same and cut recordings of foreign speech into chunks ranging between 30 and 960 milliseconds in length.  Researchers found that the shorter the speech quilt the greater the disruption to the speech's original structure. 

The researchers then played the speech quilts to the participants while they underwent brain scans.  They found that the superior temporal sulcus or STS is the region of the brain which became very active when the 480 and 960 millisecond quilts were played, but they noticed that same area of the brain was not active during the 30 millisecond quilt.

Assistant research professor of psychology and neuroscience at Duke University and coauthor of the study, Tobias Overath says, "That was pretty exciting. We knew we were onto something."

For the first time, researchers have been able to observe the STS which works to integrate auditory and other sensory information responding to time structures in speech.

The researchers have tested other control sounds that mimicked speech to back up their findings.  The control stimuli were also arranged into quilts and then it was played to the participants in the study.  Researchers noted that the same region of the brain did not respond to the control quilts.

While much is known about human speech and he brain, this recognition of time in the STS as it relates to speech is definitely groundbreaking and could help scientists treat injury to the brain that results in speech disruption.  The new study appeared recently in the journal Nature Neuroscience.