研究人员寻找口吃背后的生物学原因

Researchers are looking into the biological causes of stuttering. Stuttering is a speech problem that causes the speaker to repeat the beginning sound of some words.

For centuries, people have feared being judged for stuttering. It is a condition often misunderstood as a psychological problem caused by things like bad parenting or emotional trauma. But research presented at a recent science conference explores its biological causes: genetics and brain differences.

Stuttering affects 70 million people around the world, including U.S. President Joe Biden. Biden has spoken publicly about being bullied by classmates for his speech problem. He has said that overcoming his stutter was one of the hardest things he ever did.

After a campaign event in 2020, he met a New Hampshire teenager who also stuttered, Brayden Harrington. They ended up talking for an hour.

Living with a stutter has not been easy, Brayden told The Associated Press.

"I want to carry on what Joe Biden said to me," he said. "That this does not define you and that you can be much more than you see yourself as."

Why do people stutter?

Stuttering has been recorded as far back as ancient China, Greece and Rome. But no one really knew what caused it until modern genetic science and brain imaging helped provide some answers.

Researchers identified the first genes strongly linked to stuttering more than a decade ago. Imaging studies looked at brains of adults and older children. And in the last few years, University of Delaware researcher Ho Ming Chow started looking at 3- to 5-year-olds. That is around the age many kids begin stuttering, with about 80 percent outgrowing it.

Chow said the imaging shows small brain differences in young children who keep stuttering, compared with those who recover or those who never stuttered. He discussed his research earlier this month at a conference of the American Association for the Advancement of Science.

For example, Chow and his team found that genetic mutations related to stuttering are linked to structural problems in the corpus callosum and thalamus areas of the brain. The corpus callosum is an area that connects the two sides of the brain and helps them communicate. The thalamus sends sensory information to other parts of the brain. Past research has also linked stuttering to the basal ganglia, a group of brain structures involved in body movements.

Though several genes may be involved and the exact genetic causes may vary by child, "they probably affect the brain in a similar way," Chow said.

Still, many people incorrectly believe that people stutter because they are nervous or suffered childhood trauma. Some also think stutterers could stop if they just tried harder.

"We have a long way to go" to change such beliefs, said University of Maryland researcher Nan Bernstein Ratner.

Moving ahead

Speech therapy is currently the main way to treat stuttering. But the medications now being tested could be approved for stuttering in the next few years.

Studies have suggested that stuttering may be related to high levels of a chemical in the brain called dopamine. Some medicines reduce dopamine activity or block its action.

Holly Nover is a speech pathologist and member of the National Stuttering Association. She grew up trying to hide her stutter. Her 10-year-old son, Colton, also has a speech problem.

She said many people will surely be interested in trying stuttering medications. But not her. She is happy with her life as it is and says she has accepted her stuttering. If Colton were struggling and wanted to try medication as a teenager, however, she would be open to the idea.

Brayden, who is now 14, does not plan to try medication.

Taking medicine is "just taking away a part of you...taking away part of your personality," he said.

I'm Dan Novak.

Dan Novak adapted this for VOA Learning English from reporting by The Associated Press.

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psychological — n. of or relating to the mind

trauma — n. a very difficult or unpleasant experience that causes someone to have mental or emotional problems usually for a long time

bully — n. someone who frightens, hurts, or threatens smaller or weaker people

mutation — n. a change in the genes of a plant or animal that causes physical characteristics that are different from what is normal