University of Oklahoma research indicates that the brain relies on real-time hearing to guide complex speech motor skills, with implications for speech therapy.
When individuals cannot hear their own voices, their tongue movements become less precise during speech, according to research from the University of Oklahoma. The study, published in the Journal of Speech, Language, and Hearing Research, provides direct evidence that could help guide therapies for restoring speech control in people with hearing loss or those affected by tongue cancer.
The research, led by Matthew Masapollo, PhD, an assistant professor at the OU College of Allied Health, addresses how much the auditory system is relied upon to produce speech.
“Speech feels automatic, but it’s one of the most complex motor skills that we routinely perform,” says Masapollo in a release. “What we’ve shown in this study is that auditory information helps regulate the control of the movements.”
Methodology and Findings
In the study, researchers used electromagnetic articulography to track tongue and jaw movements as participants produced the sounds “ta” and “da.” The experiments were conducted both when participants could hear their own voices and when their hearing was masked.
The results showed a selective effect. When hearing was masked, tongue-elevating movements—which press the tongue against the roof of the mouth—became more variable and less precise. Jaw motion, however, was not affected.
“The effect was strongest during tongue-elevating movements, rather than overall tongue motion,” says Masapollo. “This suggests the brain doesn’t fully pre-plan speech movements; it also relies on real-time sensory information to regulate tongue movements for speech.”
The study suggests that highly malleable structures like the tongue require more sensory input to regulate their control for speech compared to less flexible structures like the jaw.
Clinical Implications for Rehabilitation
The findings are relevant for individuals with hearing loss, including those with cochlear implants, and are informing a new study by Masapollo involving patients treated for tongue cancer at OU Health Stephenson Cancer Center. Cancer treatments such as chemotherapy can damage hearing, while surgery and radiation can impair the tongue’s structure and flexibility.
“The sensory nerves of the tongue are often damaged during surgery, and radiation creates a lot of fibrous tissue in the tongue,” he says. “People who have part of their tongue removed may also have trouble swallowing. When we swallow, the tongue rises to press against the roof of the mouth, forming a tight seal—similar to the tongue movements used to produce the sounds ‘ta’ or ‘da’.”
Masapollo aims to track patients’ motor impairment trajectories before and after treatment to understand how surgery and radiation affect tongue control. The ultimate goal of the research is to provide data that could help speech pathologists and occupational therapists improve speech rehabilitation strategies for their patients.
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