Researchers report new evidence about why some mammals can control their voices while most cannot. The study, published in Science and led by Emory University and New College of Florida, compared coyote brains with those of three pinniped species: California sea lions, harbor seals and northern elephant seals. The team used diffusion magnetic resonance imaging on postmortem brains to map neural pathways related to vocal control.
The project examined four California sea lions, four harbor seals, three northern elephant seals and four coyotes. All brains came from wild animals that died naturally at rehabilitation centers or were euthanized for injuries, or from coyotes euthanized at a United States Department of Agriculture facility in Utah. The diffusion MRI method for non-living brains was developed by Karla Miller at the University of Oxford. Gregory Berns and Peter Cook applied the method to map 15 brain regions involved in vocal control.
Results revealed a clear difference in wiring. In coyotes the mid-brain, which controls automatic survival behaviours, links to brainstem cells that drive vocal muscles. In the pinnipeds the vocal motor cortex connects directly to the brainstem, bypassing the mid-brain. This bypass can give conscious control of the larynx and may allow vocal learning. The data also showed strong auditory–vocal connections in elephant and harbor seals but not in coyotes; harbor seals had especially strong thalamus–vocal motor cortex links, a pattern seen in parrots and humans and possibly related to mimicry. Famous pinniped examples include Hoover, a harbor seal that mimicked a Boston accent, and experiments that trained gray seals to imitate human tunes.
Researchers suggest the bypass evolved as seals and sea lions developed precise breath and swallowing control for underwater life. Sea lions can stay underwater for an average of 10–20 minutes while some seal species can dive without surfacing for up to two hours. Cook said, “We’ve discovered an ecological recipe for how a mammal might evolve a vocally flexible brain.” Berns added that comparing more species could help build an evolutionary tree for language. The team plans similar studies in whales, dolphins and porpoises.
Difficult words
- neural pathway — nerve routes carrying signals between brain areasneural pathways
- brainstem — lower part of brain controlling basic body functions
- vocal motor cortex — brain area that plans and controls vocal muscles
- diffusion MRI — imaging method that traces movement of water moleculesdiffusion magnetic resonance imaging
- mimicry — copying another animal's sounds or behaviours
- bypass — route that avoids a usual intermediate structure
- vocal learning — ability to learn or modify vocal sounds
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Discussion questions
- How might direct connections from vocal motor cortex to brainstem help seals learn or control sounds? Give reasons or examples from the article.
- The researchers plan to study whales, dolphins and porpoises next. How could comparing more species help build an evolutionary tree for language?
- The brains came from wild animals that died naturally or were euthanized. What ethical issues should scientists consider when using such samples in research?
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