Stuttering: A Neurobiological Breakdown of Speech Fluidity

Imagine if a seemingly innocuous thought — such as the notion of speaking — triggered a response that left you in fear of all social situations. Now imagine it initiating a chain reaction which caused tension in the jaw, involuntary muscle movement, and increased heart rate, and brought on bouts of anxiety that exacerbated your inability to produce fluid speech. What makes this painful paradigm worse is that when you’re alone, you’re fluent.


Our ability to speak is often perceived as one of our most rudimentary human functions. Just as we view our bodies as operating with mechanical fluidity, our capacity to use language is a marvelous and vital gift that is often taken for granted. After all, we are unable to recall the amount of time and effort it took us to absorb our first language, so speaking is often regarded as something that just is. However, this dexterous skill we use to construct and produce fluid language can be disengaged — and for over 3 million people, speech disfluencies and language disorders are not only emotionally exhausting but also a daily struggle.

When we speak, we produce sound through precise muscle coordination that includes breathing, phonation, and enunciation. The brain governs our muscle movements while monitoring our sense of hearing and touch; the basal ganglia and the striatum are involved in the even timing and planning of speech; and the left hemisphere is the primary center at work in producing the fluency of language. According to Dr. Barry Guitar, a professor of communications and science at the University of Vermont, “The left hemisphere … is where many of the brain’s speech-centers are. In some people, these structures are not organized efficiently, and stuttering can result.” Though the precise cause of the disfluency is still unknown, researchers believe that in the brain of a stutterer regions of the left hemisphere never fully develop, causing the right hemisphere to become overactive. The longer a person stutters, the more the right hemisphere compensates for the left, causing a greater disproportion. “To compensate, the right hemisphere will try to take over,” says Guitar. “This has been shown in many brain-imaging studies of stuttering. But because the right hemisphere is not designed for the speech centers, its attempt to compensate doesn’t work.”

In addition to teaching, Guitar — himself a stutterer — has been working with stuttering and language disorders for over 40 years and is the author of “Stuttering: An Integrated Approach to Its Nature and Treatment.” “I think that for many of us who continue to stutter beyond childhood,” he says, “there is another important factor: increased sensitivity of temperament that makes us react to the basic speech disfluencies … with tension, struggle, and fear.” A common misconception about stuttering is that the primary issue is caused by psychological problems, emotional trauma or nervousness; however, this is not the case.

Researchers believe that stuttering can lead to anxiety, as it becomes anticipatory, making the very act of speaking or even the thought of speaking stress-producing. Individuals who stutter tend to face greater levels of stress when faced with the task of spoken speech. But while they have higher levels of anxiety, anxiety is not the underpinning source of stuttering.

Though it is thus far impossible to detect who will develop stuttering, genes are playing an intricate role in deciphering the complexities of this disorder. In a study published in the New England Journal of Medicine, researchers discovered a gene mutation that is strongly linked to stuttering and can account for 9 percent of all stuttering cases. In his book, Guitar writes, “Researchers looking at families and communities with large concentrations of individuals who stutter have identified seven different chromosomes that appear to be associated with stuttering. One of these chromosomes has been shown to carry three genetic mutations, one of which is associated with motor control and emotional regulation.” Though only 1 percent of the population stutters, studies have shown that 60 percent of these individuals also have family members who have or have had the disorder.

“Stuttering is not just a disorder of the mouth, tongue, and throat,” says Dr. Gerald Maguire, director of the Kirkup Center for the Medical Treatment of Stuttering at the University of California, Irvine, “but a disorder of the brain that coordinates the mouth, tongue, and throat to speak.” Maguire’s center studies the neurobiology of stuttering. “We found that dopamine brain chemicals are elevated in the brains of some individuals who stutter,” he says, “and our center has been utilizing medicines that block or modulate levels of dopamine in the brain to improve stuttering.” Maguire’s research has shown that since the striatum is central to the timing and initiation of speech — and is under the influence of dopamine — inhibiting the levels of dopamine might allow for fluency in many individuals who stutter.

Though a single pill is unlikely to be a cure-all for the aliment, Maguire and his research team are getting closer to discovering a way to medically treat the disorder. In fact, Maguire has himself been on one of these medicines for the past 20 years. He also credits speech therapy, public speaking and a self-help group run by the National Stuttering Association. The Kirkup Center primarily utilizes medication, but also applies cognitive behavioral psychology and speech therapy.

It is not uncommon for many young children to develop a form of stuttering in their early phases of development. Studies have shown that one in 20 children will go through trouble with fluency, and many that develop stuttering will eventually outgrow the disorder. Many speech-language pathologists encourage parents to talk to their children in a slow and relaxed manner, and also suggest that parents set aside a few minutes a day to have one-on-one conversations that are accepting and encouraging. It is important that children feel supported and relaxed. Do not demand that your child speak a certain way in front of people, and refrain from speaking negatively when the child stutters as this has the possibility to exacerbate their condition. “When we work with a preschool child, we guide the parents in working directly with their children’s speech on a daily basis,” writes Guitar. “More often then not, this leads to complete (or near-complete) recovery from stuttering.”


Many current therapies are being offered to stutterers which help with breathing techniques and learning ways to speak more slowly. It is also important to remember that if you are suffering from stuttering, you’re not alone. Stuttering is a common disorder and Maguire believes that many people who suffer from it do so in silence. “We are developing newer and better treatments every day, and there are great resources in the National Stuttering Association,” he says. The NSA is a nonprofit group which offers support at a local level. “Don’t feel ashamed about your stuttering,” says Maguire. “This is not a disorder that was brought on by bad parenting or being too nervous as a child. We now know that this is a disorder of the brain, and we are developing better treatments.”

This article was originally published in the Winter 2013 issue of Brain World Magazine.

Related Articles


Be the first to comment

Leave a Reply

Your email address will not be published.


*