Scientists have found the first evidence that the ability to learn vocalizations, a capacity so far believed to be restricted to a handful of bird and mammal species like humans and dolphins, is shared by another species: mice. The new research, published Oct. 10 in the open access journal PLOS ONE by Erich Jarvis and Gustavo Arriaga at Duke University and colleagues, shows for the first time that mice share certain behavioral and brain mechanisms involved in vocal learning with songbirds and humans and can learn new vocal patterns.
Most animals make sounds of some sort, but only a few have the capacity to modify the sequence and pitch of sounds to create songs and speech, collectively referred to as vocal learning. So far, only three groups of birds -- parrots, hummingbirds and songbirds -- and some mammalian species -- humans, whales, dolphins, sea lions, bats and elephants -- have shown the behaviors and brain circuits that are considered essential to the process of learned vocalization. Despite decades of research, scientists have yet to find evidence of these behavioral and neurological hallmarks in other species, including those closely related to vocal learners such as non-human primates.
Though the series of ultrasonic vocalizations referred to as mouse 'song' was previously known, this study provides the first evidence that mice can change at least one acoustic feature of these vocalizations based on their social exposure. When two male mice of different strains were housed together, the animals gradually learned to match the pitch of their songs to one another, suggesting a capacity for learning not previously known. The researchers state that this is a limited form of vocal learning, but do not know whether other more complex features, such as syntax and frequency modulation, could be learned.
The researchers found that mice can form some of the necessary connections between different brain regions and the vocal motor neurons to control the sounds they make, a feature so far found in song learning birds and humans. Though the connections are more limited in mice compared to humans or songbirds, Jarvis states, "This is an exciting find, as the presence of direct forebrain control over the vocal neurons may be one of the most critical aspects in the human evolution of speech."
According to the researchers, their discovery was made possible by using modern techniques not previously available. They also clarify that the connections in mice are much more primitive than in songbirds or humans, but they may reveal some of the intermediate steps in the process by which vocalization evolved in advanced vocal learners like songbirds and humans.
Mouse songs are included in the PLoS article. See citation below.
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