The vocal sounds of humans -- laughing, crying, and the babbling of babies -- have the same rhythmic quality as the sounds made by many mammals, songbirds, and even some species of fish. Researchers at UC San Francisco have discovered that a small cluster of neurons in the brain stem not only regulates tempo but also coordinates vocalization with breathing.
"Just to laugh or shout, the body has to coordinate about 100 different muscles in a rhythmic pattern within a single breath," said Kevin Yackle, MD, PhD, a Sandler Faculty Fellow and senior author of the study published online Jan. 7, 2022, in Neuron. "We discovered the neurons that, when switched on, give us this unconscious ability." It's been widely understood that many animals, including humans, have innate control of breathing -- you don't have to use your brain to do it. Yackle and his team suspected that the same control exists for innate vocalizations. To confirm the existence of this brain circuit, Yackle and his team studied the sounds made by baby mice when they were separated from their mothers. The babies' cries had a recognizable pattern associated with specific muscle movements. The researchers then determined which cells in the brain stem were responsible for this rhythm, which turned out to be a previously unknown circuit that appears to control the breath and coordinate the muscles needed to produce the vocal sounds. Identifying this system will enable scientists to ask new questions about how we speak and why some people have trouble doing it. Read more...
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