Zeroing in on the brain's speech 'receiver'

Jun 20, 2007

A particular resonance pattern in the brain’s auditory processing region appears to be key to its ability to discriminate speech, researchers have found. They found that the inherent rhythm of neural activity called “theta band” specifically reacts to spoken sentences by changing its phase. The researchers also noted that the natural oscillation of this frequency provides further evidence that the brain samples speech segments about the length of a syllable.

The findings represent the first time that such a broad neural response has been identified as central to perceiving the highly complex dynamics of human speech, said the researchers. Previous studies have explored the responses of individual neurons to speech sounds, but not the response of the auditory cortex as a whole.

David Poeppel and Huan Luo published their findings in the June 21, 2007 issue of the journal Neuron, published by Cell Press.

In their experiments, the researchers asked volunteers to listen to spoken sentences such as “He held his arms close to his sides and made himself as small as possible.” At the same time, the subjects’ brains were scanned using magnetoencephalography. In this imaging technique, sensitive detectors are used to measure the magnetic fields produced by electrical activity in brain regions.

Poeppel and Luo pinpointed the theta band—which oscillates between four and eight cycles per second—as one that changed its phase pattern with unique sensitivity and specificity in response to the spoken sentences. What’s more, as the researchers degraded the intelligibility of the sentences, the theta band pattern lost its tracking resonance with the speech.

The researchers said their findings suggest that the brain discriminates speech by modulating the phase of the continuously generated theta wave in response to the incoming speech signal. What’s more, they said, the time-dependent characteristics of this theta wave suggest that the brain samples the incoming speech in “chunks” that are about the length of a syllable from any given language.

Source: Cell Press

Explore further: Mystery of the reverse-wired eyeball solved

add to favorites email to friend print save as pdf

Related Stories

Korean tech start-ups offer life beyond Samsung

20 hours ago

As an engineering major at Seoul's Yonsei University, Yoon Ja-Young was perfectly poised to follow the secure, lucrative and socially prized career path long-favoured by South Korea's elite graduates.

NASA satellite sees a warm winter in the Western US

5 hours ago

While people in the eastern two-thirds of the U.S have been dealing with Arctic Air, the bulge in the Jet Stream over the eastern Pacific Ocean has been keeping the western third of the U.S. in warmer than ...

Recommended for you

Mystery of the reverse-wired eyeball solved

2 hours ago

From a practical standpoint, the wiring of the human eye - a product of our evolutionary baggage - doesn't make a lot of sense. In vertebrates, photoreceptors are located behind the neurons in the back of the eye - resulting ...

Neurons controlling appetite made from skin cells

2 hours ago

Researchers have for the first time successfully converted adult human skin cells into neurons of the type that regulate appetite, providing a patient-specific model for studying the neurophysiology of weight ...

Quality control for adult stem cell treatment

5 hours ago

A team of European researchers has devised a strategy to ensure that adult epidermal stem cells are safe before they are used as treatments for patients. The approach involves a clonal strategy where stem cells are collected ...

A gene for brain size only found in humans

7 hours ago

About 99 percent of human genes are shared with chimpanzees. Only the small remainder sets us apart. However, we have one important difference: The brain of humans is three times as big as the chimpanzee ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.