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Stuttering

Tongue Twisters Reveal Quirky Brain Functions

Can you say “pad kid poured curd pulled cod” ten times fast? Most people can’t.

New research on the neuroscience of tongue twisters—and stuttering—offers many insights into brain function and connectivity. Both tongue twisters and stuttering open windows into the brain's speech-planning processes.

A team from the Massachusetts Institute of Technology (MIT) is reporting new findings on brain function based on the comparison of two types of tongue twisters at the 166th meeting of the Acoustical Society of America (ASA) in San Francisco this week. These findings build on previous research to help better understand the specific brain connectivity behind the complex timing and syncopation needed to speak a language.

In another study, researchers discovered specific changes in the connectivity between brain regions that cause some people to stutter when they speak, and solves the riddle of why chronic stutterers—like country singer Mel Tillis—can usually sing song lyrics without a stammer.

Can You Say “The Top Cop Saw a Cop Top” Ten Times Fast?

Stefanie Shattuck-Hufnagel, an MIT psychologist who is presenting the work at ASA, studies speech errors as a way of understanding normal brain functions. "When things go wrong, that can tell you something about how the typical, error-free operation should go," she said. In their recent study, the team from MIT, and colleagues, tried to determine whether they could induce different types of double onset with different types of tongue twisters.

There are certain combinations of sounds and phrases that cause people's tongues to get jumbled up. The brain seems to momentarily lose cooridination and control of the mouth. Often, one sound will replace another ... "Toy Boat" becomes "Toy Boyt"..."Top Cop" becomes "Cop Cop”... And, in the doozy of them all, "The Seething Sea Ceaseth and Thus the Seething Sea Sufficeth Us," becomes alphabet soup of misplaced "S's" and "Th's."

The MIT researchers recorded volunteers saying combinations of alternating words that fell into two categories: simple lists of words, such as the "Top Cop" example above—and full-sentence versions of the same sounds with an inversion, such as "The Top Cop Saw a Cop Top."

One particular list of words turned out to be so difficult that test subjects couldn't get through it. That phrase was: "Pad Kid Poured Curd Pulled Cod." When volunteers tried to say this multiple times, Shattuck-Hufnagel said, some of them simply stopped talking altogether. "If anyone can say this [phrase] ten times quickly, they get a prize," she said.

The researchers hope to use this work to find the ghosts of double onsets, in which the tongue has tried to make both a "T" and "K" but only one sound is heard. If these double onsets are indeed more likely to be produced by "word list twisters" than by "sentence twisters," Shattuck-Hufnagel believes this work will help scientists understand how the brain plans these two types of speech.

My brain and mouth go haywire whenever I try to say, “As the Crow Flies.” I use this phrase somewhat regularly to describe the 135-mile Badwater ultramarathon through Death Valley which I’ve done a few times. Almost always, I will accidentally say the phrase as a spoonerism, “As the Flow Cries." People listening will look at me strangely and ask, "What does flow cries mean?" Even with the explicit knowledge, I get tripped up on this phrase, implicitly I continue to automatically make the mistake of flipping the "Fl" and "Cr". Do you have certain word combinations or phrases that regularly trip you up or consistently become spoonerisms?

Males are Four Times More Likely to Be Chronic Stutterers

According to The Stuttering Foundation, roughly 1% of the population are stutterers, while 5% of the population have stuttered at some point in their life. Gender is one of the strongest predisposing factors for stuttering. Did you stutter at any point in your life? Do you still stutter?

Statistically, stuttering affects many more males than females. In older children and adults the male-to-female ratio is about 4-to-1. Boys also have a greater risk for developing chronic stuttering. In children who became chronic stutterers, there are 3.75 boys to each girl. Interestingly, young girls who stutter have a much greater chance than boys to experience natural recovery without treatment. 

Stuttering Essential Reads

As a separate point of interest, geneticists and neuroscientists are also busy looking for clues as to why boys are 5 times more likely than girls to suffer from autism spectrum disorders (ASD). 

Why are boys almost four times more likely than girls to stutter? Surely there are a wide range of neurobiological, envrionmental and social reasons, but much of the sex difference in stuttering is based on neural connectivity between various brain regions. A 2007 study from UCSF found the stutter-rate was generally right-sided in males, but bilateral between the left and right cerebral hemispheres in females.

For both sexes, there were positive correlates to stuttering in the right anterior insula and negative correlates in the right Brodmann area 21/22 and within the left hemisphere’s inferior frontal gyrus. Compared to female stutterers, male stutterers had much stronger connectivity between regions of the left cerebrum and the right cerebellum.

This type of brain connectivity could offer clues as to why males are four times more likely to stutter than females. A UPenn study from December 2013 found major differences of neural connectivity within and between the cerebrum and cerebellum based on gender. My Psychology Today blog post “Brain Connectivity Varies Between Men and Women” explores this research in detail. 

The Cerebellum’s Role in Speech and Song

The cerebellum is strongly involved with aspects of controlling both speech and singing. Another study published in The Cerebellum journal showed that the left hemisphere of the cerebellum is specialized for singing and right hemisphere of the cerebellum is specialized for speech.

Given the crossed pattern of connectivity, the findings are consistent with the hypothesis that the right cerebellum mostly processes segmental properties of speech, and the left cerebellum processes the rhythmic aspects of language and melodic properties.

There are a considerable number of hypotheses about the underlying function of the cerebellum in speech—from tongue twisters to stuttering. Recently, the cerebellum has been shown to be involved with sharpening sensory input, temporal coordination and processing of motor articulation and perception, as well as instantiation of internal models that simulate the input-output characteristics of a specific system in song vs. spoken word.

Singing language and speaking language share many common features. Although the two forms of vocalization differ in certain vocal and rhythmic aspects. A review of the literature on perception and production of singing and speech revealed considerable overlap in specific areas of the cerebellum, which control the timing and movement of the lips and tongue.

Interestingly, the singer Carly Simon has spoken of learning to overcome her stammer as a child by tapping her thighs while rhythmically learning to say things like “Please pass the butter” in a sing-song way at the dinner table. If you’d like to read more on this, check out my Psychology Today blog post “Musical Training May Improve Brain’s Language Skills.”

Conclusion: Tongue Twisters and Stuttering are Linked to Brain Connectivity

A 2012 study from China found that just one week of speech therapy can help reorganize brain connectivity and reduce stuttering. The researchers were able to hone in on the role of neural connectivity between different brain regions as linked to stuttering.

Brain scans were used to measure the thickness of the cerebral cortex in the brain for all participants at the beginning and end of the study. They also measured the interactions between areas of the brain while at rest called "resting state functional connectivity." In people who stuttered, the thickness and strength of interactions was reduced in an area of the brain important in speech and language production called the pars opercularis. Stutterers also had an atypical level of connectivity in the cerebellum.

This hyper-connectivity between the cerebellum and the cerebrum indicated a strong link to stammering. For those who received the therapy, the functional connectivity in the cerebellum was reduced to the same level as that of the controls. There was no change in the pars opercularis area of the brain.

"These results show that the brain can reorganize itself with therapy, and that changes in the cerebellum are a result of the brain compensating for stuttering," said study author Chunming Lu, PhD, of Beijing Normal University in China. "They also provide evidence that the structure of the pars opercularis area of the brain is altered in people with stuttering."

Christian A. Kell, MD, of Goethe University in Frankfurt, Germany, who wrote an editorial accompanying the study, said, "These findings should further motivate therapists and researchers in their efforts to determine how therapy works to reorganize the brain and reduce stuttering."

If you'd like to read more on this topic, check out my Psychology Today blog posts:

Follow me on Twitter @ckbergland for updates on The Athlete’s Way blog posts.

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