Nervousness and anxiety can get the best of us when we're talking on the phone or speaking in front of a crowd. Words start to come out in fragments as we falter, halt, and hesitate to repeat ourselves to sound more clear. This may be triggered by a bad case of the nerves for some of us, but for over 3 million Americans in the United States, stuttering interferes with daily life.
Researchers at the Children's Hospital Los Angeles (CHLA) have revealed this lifelong vulnerability in children and adults is linked to reduced blood flow in a specific brain region linked to language.
"Blood flow was inversely correlated to the degree of stuttering — the more severe the stuttering, the less blood flow to this part of the brain," said Dr. Jay Desai, MD, a clinical neurologist at CHLA, in a statement.
Previous research done by Dr. Bradley Peterson, lead author of the current study, has shown there is a link between stuttering and changes in the brain circuits that control speech production, as well as those supporting attention and emotion. The disturbances in these speech processing areas in the brain may be a cause of stuttering.
CHLA researchers know blood flow is typically coupled with neural activity, which compelled them to zero in on a specific brain region — the Broca's area — in the recent study published in Human Brain Mapping. This region is located in the frontal lobe of the brain, which is linked to speech production. Brain circuitry, specifically linked to speech, was also examined while using regional cerebral blood flow as a measure of brain activity.
The blood flow measurements revealed that other portions of the brain circuit related to speech were also affected, and led to more severe stuttering in both children and adults. Overall, the more the stuttering, the less blood flow was seen in this part of the brain. The researchers suggest there is a common pathophysiology throughout the neural "language" loop that connects the frontal and posterior temporal lobe which likely contributes to stuttering severity.
Peterson, also a director of the Institute for the Developing Mind at CHLA, and a professor of the Keck School of Medicine at the University of Southern California, believes this is "a critical mass of evidence."
A study of resting blood flow, or perfusion, has never before been conducted in people who stutter, according to Peterson. The findings suggest disturbances in the speech processing areas of the brain are likely of central importance as a cause of stuttering.
Stuttering has been attributed to other factors, including genetics, child development, and family dynamics. The speech disorder may occur when a combination of factors come together, and may have different causes in different people, according to The Stuttering Foundation. There could be a difference in what causes stuttering, and what makes it continue or get worse.
Currently, there is no cure to stuttering, but researchers have been testing new approaches, such as the Modifying Phonation Intervals (MPI) Stuttering Treatment Program that teachers stutterers to reduce their frequency with how they produce very short intervals of phonation while speaking. For example, in the word “shout,” for example, “out” is a voiced (phonated) unit; “sh” is an unvoiced unit. The MPI program software delivers real-time feedback to the person showing the occurrence of the short phonated intervals so they can learn how to reduce their stuttering.
The program is divided into four phases, which is designed to be managed by the stutterer and their clinician. The effectiveness of this program has shown to reduce the frequency of stuttering, resulting in natural fluent speech for most participants in clinical trials. However, the researchers do acknowledge it’s not an overnight fix; it can take months to show improvement throughout the different phases.
Researchers have gained a deeper understanding in the underlying mechanisms that lead to stuttering, which can aid the development of treatments that help limit the disorder’s severity for patients.
Source: Desai J, Huo Y, Zhishun W et al. Reduced perfusion in Broca's area in developmental stuttering. Human Brain Mapping. 2016.