Scientists look beyond speech to understand the seemingly simple stutter

By Allison McCann

Speaking with a mouthful of pebbles didn’t cure the stutter of King George VI in real life or in the recent historical drama “The King’s Speech.” And today, scientists are still trying to develop effective therapies for stuttering, the focus of a session on Feb. 20 at the 2011 AAAS meeting in Washington, D.C.

That starts with pinpointing the origins of the disorder. Speech and language experts are using brain imaging, genetics studies and evaluations of early-onset stuttering in children to try to explain how and why a stutter develops.

Is it a traumatic event or harsh parenting that triggers the speech impediment, as commonly believed? No scientific evidence supports that idea, said Nan Ratner, a professor of hearing and speech sciences at the University of Maryland.

“We really don’t have good predictors,” said Anne Smith, a professor of hearing and speech sciences at Purdue University. “The aim of our project is to determine if there are physiological or behavioral measures to determine the likelihood of persistence or recovery.”

Physically, stuttering results from a breakdown in the systems that control speech production, but the causes may be linguistic, cognitive, psychosocial or genetic. Nearly three million Americans stutter, and the disorder occurs most often in boys age 2 to age 5, according to the National Institute on Deafness and Other Communication Disorders.

Seventy-five to 80 percent of children age 2 to age 4 who develop a stutter will recover, and that is mainly through therapies that teach youngsters not to fight or ignore the stutter, Smith said.

Children who start stuttering very early in life and continue to do so for a long time can help researchers understand why some people are able to overcome a stutter whereas others are not.

“Adults who stutter have been doing it since age 3 or 4,” Smith said. “So if we want to know what the causal factors are, we’ve got to look at little kids.”

Smith has found basic differences between how children with a stutter and those without carry out simple non-speech movement tasks such as clapping along with a rhythm.

Such tasks are helping to answer questions about which factors influence the early development of stuttering and who will be able to recover. This knowledge will help guide treatment decisions.

Other researchers are focusing their efforts on better understanding the activity of the brain and nerves during fluent speech production. Through techniques such as functional Magnetic Resonance Imaging, which monitors blood flow to different parts of the brain, Luc De Nil, a professor of speech and language pathology at the University of Toronto, has been able to compare which brain areas are activated in people who have a stutter and in those who don’t.

He has found that stuttering speakers have much more brain activation than others. There are also subtle variations in the makeup of the brain.

“There are differences at the neural level in both children and adults, some of which are structural,” De Nil said. “But people who stutter also show deficiencies in coordination mechanisms in areas of motor activity that have nothing to do with speech.”

Dennis Drayna, a researcher from the National Institutes of Health, is also using non-speech methods to unlock the mystery of stuttering. He has taken his research all the way to Pakistan to study highly inbred families whose history of stuttering suggests a genetic link.

So though the condition manifests itself through speech, as seen in King George VI’s initially tortured dialogue, the breakdown can occur far away from the mouth and tongue.

“Stuttering isn’t just these behaviors you see, it is some profound differences in the way the brain is forming its neural connections during development,” Smith said. “An infant is not born with the wiring needed for normal language production. That’s something wired up during development. Certainly, genes guide that wiring, but there’s no fixed path to stuttering."

Allison McCann is a senior pursuing a B.S. degree in science, technology and society and a minor in communication at Stanford University. She is a writer for the student-run publication Stanford Scientific Magazine, and she is pursuing a career in science writing. Reach her at atmccann@stanford.edu.

February 24, 2011

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