Speech uses both sides of brain

Date: Jan-17-2014Many scientists believe we only use one side of our brain for speech and language.

Now, a new study from the US shows that as far as speech is concerned, we use both

sides.

The study poses a significant challenge to current thinking about brain activity and could

have important implications for developing treatment and rehabilitation to help people recover

speech after stroke or injury, say the researchers from New York University (NYU) and NYU

Langone Medical Center.

Senior author Bijan Pesaran, an associate professor in the Center for Neural Science at NYU,

says:

"Our findings upend what has been universally accepted in the scientific community - that we

use only one side of our brains for speech. In addition, now that we have a firmer

understanding of how speech is generated, our work toward finding remedies for speech

afflictions is much better informed."

Speech rarely studied separately from language

As well as listening and speaking, speech involves language for constructing and

understanding sentences. Thus most studies conclude that speech, like language, happens on one

side of the brain. And these studies rely on indirect measurement of brain activity, explain

the researchers.

For their study, they took a different approach and examined the link between speech and

brain processes directly.

The data for the study came from a group of patients being treated for epilepsy. They had

electrodes implanted directly inside and on the surface of their brains as they performed

sensory and thinking tasks.

Co-author Thomas Thesen, director of the NYU ECog Center where the data was collected, and

an assistant professor at NYU Lagone, says:

"Recordings directly from the human brain are a rare opportunity. As such, they offer

unparalleled spatial and temporal resolution over other imaging technologies to help us achieve

a better understanding of complex and uniquely human brain functions, such as language."

To record what happens in the brain during speech alone that is separate from language, the

patients were asked to repeat "non-words," like "kig" and "pob."

Study shows speech is a bilateral brain process

The recordings showed that both sides of the brain were involved during speech - suggesting

that speech is a "bilateral" brain process, as the researchers conclude in their study

report:

"Using a non-word transformation task, we show that bilateral sensory-motor responses can

perform transformations between speech-perception- and speech-production-based representations.

These results establish a bilateral sublexical speech sensory-motor system."

Prof. Pesaran adds:

"Now that we have greater insights into the connection between the brain and speech, we can

begin to develop new ways to aid those trying to regain the ability to speak after a stroke or

injuries resulting in brain damage. With this greater understanding of the speech process, we

can retool rehabilitation methods in ways that isolate speech recovery and that don't involve

language."

Meanwhile, US researchers - who discovered how accurately we respond to a beat is tied to how

effectively our brains respond to speech - suggest in The Journal of Neuroscience that

musical training could improve

our brains' response to language.

Written by Catharine Paddock PhD




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