If there was a rodent opera, Alston's singing mouse would be the star. This unpretentious brown mouse, originating from the cloud forests of Central America, rises on its hind legs and pulls long, sophisticated trills. The presentation of each animal looks unique, says Michael Long, a neurologist at the New York University Medical University in New York. "I can recognize this particular song and say," Ah, this is Ralph. "t: Takes singing bends, and these quick-acting duets give the researchers a new model to explore how the brain controls the conversation Mice can even understand our understanding of what is wrong with communication disorders such as autism  The human conversation has a lot of moving parts, while listening, planning our words, setting them on the move and directing our vocal muscles to spit at appropriate social moments. "Most laboratory animals do not have this complex complexity, says Long. Mus musculus has a relatively inorganic and unpredictable song and is not reluctant to alternate.Although marmosets, primates with calls that make them popular in neuroscience research, stop for a few seconds between the answers, meaning that they can not rely on the same nervous mechanism that manages second-hand responses in humans, she says. "Imagine a conversation between two people where there is a 5-second pregnancy pause between each exchange. I think I will go mad. "
That's why he and other researchers are interested in Alston's singing mouse. The social functions of his distinctive songs are not yet fully clear. (The performance seems to be part of a territorial display, although it can not always be competitive.) The relatively newcomer in neuroscience is a little wild in the lab, requiring a spacious terrarium, a specialized diet and training equipment to thrive. But Long and his team have found an intriguing trend for mice. When a male mouse enters a room adjacent to another man and can hear his neighbor singing, the time changes to avoid overlapping with the neighbor; it begins about half a second after the completion of other mice. (In human conversation, the lag is even shorter – an average of about 200 milliseconds.) The mouse with a neighbor also sings four times more than when alone, the researchers found.
Researchers wanted to know how the brain of the mice carefully controlled the exchange. Many studies have shown that animal vocalizations come from deep, evolutionary ancient parts of the brain – the so-called subcortical structures. But they wondered whether in this singing mouse, a separate structure in a higher field, called a crust, acted as a conductor of the orchestra, turning the songs into and excluding on the basis of social signals. First, they identified a part of the brain called the orofacial motor crust (OMC), which, when stimulated, forced the mouse to shrink its voice muscles. When they placed a cooling device on this region to slow down its neuronal activity, the mouse took longer to finish the song.
Moreover, mice could still sing when scientists gave them a drug that completely inactivated the OMC – vocalizations were apparently produced elsewhere in the brain, but listening to the song of another mouse did not increase their own singing anymore. And mice have not started a swift "counter track" in response, researchers report online today at Science . They conclude that in order to make a vocal transformation, the mouse's brain divides labor between a master song generator (not yet identified in the subcortical brain) and a conductor at a higher level.
"I think it's beautiful, the combination of methods they applied," says Julia Fischer, an ethnologist who studies social behavior and knowledge of animals at the University of Göttingen in Germany. "It's a breakthrough, from the point of view of the fine details … they were able to work out."
Alston's singing mouse is "a new, potentially interesting model for vocal communication," says Karel Svoboda, a neurologist at the Glenelia Institute of Investigation Corps Medical Institute in Ashbourne, Virginia. Still, he says, "We need to know a lot more." This study does not determine how the OMC influences activity in the lower brain, he notes, or how the schemes there actually make the muscles move to produce a song.
Human speech is much more complex than these mice, but Long's team now wants to look at the human brain for such a synchronization mechanism in the human motor cortex known to be involved in speech control. He and his colleagues design experiments that record brain activity during colloquial tasks such as fast response to another voice. Researchers can manipulate genes in the mouse OMC who are involved in autism to monitor how they affect brain activity and behavior. Long winners, Long says, "really broke up for us a whole new piece of biology."