Mickey Mouse Concert: Mice Can Sing Like Humans

A 60-year-old assumption that mice do not have vocal learning traits at all is being challenged.

The new finding might amuse you, as it states that mice have certain brain features (vocal communication pathways) that are similar to humans and song learning birds. Male mice try matching the pitch of other males' ultrasonic serenades.

"We are claiming that mice have limited versions of the brain and behavior traits for vocal learning that are found in humans for learning speech and in birds for learning song," said neurobiologist Erich Jarvis of Duke University and lead researcher of the study. 

 "If we're not wrong, these findings will be a big boost to scientists studying diseases like autism and anxiety disorders," said Jarvis, who is also Howard Hughes Medical Institute investigator. "The researchers who use mouse models of the vocal communication effects of these diseases will finally know the brain system that controls the mice's vocalizations."

Jarvis admits that this new finding that focuses on the mice vocalization is controversial as it challenges and contradicts the age old assumption that mice lack vocal learning traits.

"This is a very important study with great findings," said Kurt Hammerschmidt, an expert in vocal communication at the German Primate Center who was not involved in the study.

According to Hammerschmidt, if mice displayed the talent of learning of vocalization then they could be the best model to study the genetic foundation of the evolution of language.

The testing of the male mice for vocal learning traits as part of a larger project to study speech evolution in humans was done by Jarvis, his former graduate student Gustavo Arriaga, and a colleague from Tulane University.

It is known that vocal learning is unique to humans and songbirds, parrots and hummingbirds. It is defined with five features related to brain structure and behavior. And this unique factor is absent in other animals.

"I almost expected every experiment in mice to fail," Arriaga said.

For this study, Arriaga first used gene expression markers, which triggered the neurons in the motor cortex of the mice's brain as they sang. He then damaged the song-specific neurons in the motor cortex and observed that the mice failed in keeping their songs on pitch or repeat them as consistently.  Similar event occurred when mice became deaf. With the help of the injectable tracer, they mapped the signals controlling song as they moved from the neurons in the motor cortex to those in the brainstem and then to the muscles in the larynx.

"This direct projection from the mice's forebrain to the brainstem and muscles was the biggest surprise," Jarvis said.

"The evidence of direct projection from these motor cortex regions is a great finding," Hammerschmidt said. "And I think it is important to try to understand whether these projections are really able to work in a similar way like such projections known in birds and humans."

The most interesting aspect noticed by the researchers is that, when two male mice were placed in the same cage with a female, the males' pitch began to converge after seven to eight weeks. Nearly 24 male mice were tested and the experiment was conducted twice to confirm the result.

Hammerschmidt is still sceptical. Jarvis and Arriaga's "pitch convergence story is less convincing," he said. According to him, this study could be too low to determine whether the discovered effect is reliable.

More work is needed to know if mice can learn other features of vocalizations or if their learning is limited to just pitch, feels Jarvis. "Our results show that mice have the five features scientists associate with vocal learning. In mice, they don't exist at the advanced levels found in humans and song-learning birds, but they also are not completely absent as commonly assumed," he said. 

The result appears in Oct.10 in PLoS ONE and is further described in a review article in Brain and Language.