Dr. Terra Barnes listens to a recording of mouse vocalizations, modified to bring the pitch within the human auditory range, while watching a visual representation of the recording. Analysis of recordings from dozens of mice showed that mice carrying a mutation in a gene associated with stuttering in humans vocalized in an abnormal pattern similar to human stuttering. Photo by Washington University School of Medicine in St. Louis

ST. LOUIS, April 15 (UPI) -- Although stuttering has baffled scientists for centuries, researchers think they've pinned the primary cause down to a genetic mutation, which they say could eventually lead to a treatment for the condition.

Stuttering is biological in origin, though can be made worse by anxiety or stress, researchers at the Washington School of Medicine found in experiments with mice engineered to have a genetic mutation thought to be involved with the condition.


The study revealed the lack of randomness inherent to stuttering while comparing mice with and without a mutation to a gene called Gnptab.

How the gene relates to speech is unknown, because Gnptab is involved mostly with degrading molecules inside of cells, but mutations to Gnptab also have been linked to other metabolic diseases. In the mice bred to have the mutation, no other effects were found aside from stuttering.

"One of the things we find scientifically interesting about stuttering is that it is so precisely limited to speech," Dr. Tim Holy, an associate professor of neuroscience at the Washington School of Medicine in St. Louis, said in a press release. "It's a very clean defect in an incredibly complex task."

For the study, published in the journal Current Biology, researchers bred mice with mutations to the Gnptab gene that stuttered when making sounds comparable to human speech, but with no other conditions as a result of the mutation, comparing them to mice without the mutation.

Using a computer algorithm to analyze the length of pauses in spontaneous noises made by baby mice, the researchers found those with the mutation had longer pauses between noises than those without it.

The algorithm was then applied to people, finding it could distinguish between those who do and those who do not stutter, while also finding mice and people who stutter both repeated the same syllables more often in a somewhat predictable manner.

The scientists say further research will focus on how the mutation affects the complex process of speech, as well as whether the mutation's effects can be mitigated in some way.

"It's kind of crazy that this gene that's involved in digesting the garbage in your cells is somehow linked to something so specific as stuttering," Holy said. "It could be that the protein has many functions and this mutation affects only one of them. Or the mutation could very mildly compromise the function of the protein, but there's a set of cells in the brain that is exquisitely sensitive, and if you ever so slightly compromise the function in those cells you get the observable behavioral deficit."