Speech therapy: How to yell like a bat

TEXAS A&M (US) — New research that shows bats raise their voices to be heard above the crowd could lead to improved speech therapy for people with Parkinson’s disease.

Bats emit sounds and use echolocation to navigate in the dark. Like humans, bats constantly adjust the sound of their voices in a noisy environment so that they can hear themselves speak in crowded areas.

The ability to “speak up” is gradually lost in people suffering from Parkinson’s disease and effective therapies to help patients improve their communication skills has eluded researchers.



For the study, published in the Journal of Experimental Biology, researchers selected bats to study how the brain controls voice because, next to humans, “they are the loudest and most vocal animals on the planet,” says Mike Smotherman, associate professor of biology at Texas A&M University.

“All other animals, like cats and dogs, communicate with each other in simple inflexible ways and don’t have much control over the sound of their voice.”

Bats were collected from several Texas locations and their echolocation was recorded in both quiet and noisy settings. Smotherman and colleagues learned that bats will rapidly raise and lower their voices as needed in a noise environment.

The bats were then given low doses of a drug called MPTP (1-methyl-4 phenylpyridine) that caused a temporary condition similar to Parkinson’s disease. The bats lost their ability to raise their voices and to adjust their tiny chirping sounds even louder to communicate better. Unlike humans, the bats recovered within a week.

The voice changes are similar to those found in people suffering from Parkinson’s disease, who often develop speech difficulties.

“Parkinson’s disease negatively affects a person’s ability to talk, which can be one of the most frustrating aspects of the disease,” Smotherman says.

“The ability to talk like he or she used to is an especially troublesome symptom of the disease, and in fact, most people who suffer from it say their inability to communicate with their family members is the hardest part of the disease to cope with.

“By studying how the bat brain controls the sounds of the bat’s voice, it may give us better insight into how the human brain functions as well, which can improve treatment methods to deal with speech difficulties associated with such diseases as Parkinson’s.”

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