Eavesdropping on Mice's Conversations

Scientists at the Washington State University (WSU) are currently investigating the communication patterns developing between mice inside the controlled confines of their lab. Using acoustic tools, the researchers are converting the ultrasounds the rodents produce into audible noises.

Though the mice may appear at first to roam around quietly in their cages, listening in with devices specialized to pick up ultrasounds reveals an entirely different story.

Once the specialized equipment is turned on, a myriad of chirp-like sounds fills the acoustics lab. The mice are communicating by producing sounds with a frequency of well over 24,000 Hz (hertz), the maximum limit to which the human year is sensible.

Everything that goes beyond this threshold, or below 20 Hz at the other end of the spectrum, is inaudible to humans. But specialized electronics allow us to listen to these sounds, similarly to how an infrared cameras allows us to see a person's heat signature.

“The patterning of these vocalizations could be very important in determining whether or not the female mouse wants to mate with the male that is making the vocalization,” explains WSU biologist and neuroscientist Christine Portfors.

The investigator is using grant money from the US National Science Foundation (NSF) to “tune” into the rodents' conversations, in a bid to understand how these vocalizations are made.

Experts also want to learn how the mice produce these noises, and how the trait developed from an evolutionary perspective. Another goal is to understand how the animals hear these sounds.

“Humans can do this all the time where you can easily discriminate the difference between 'bad' and 'dad', and we don't know how the brain does it,” Portfors explains.

Analyzing the behavior of mice is critical for understanding and mapping their brains. This, in turn, could help neuroscientist better understand our own cortex.

In mice pairs, “it's all about female choice. The males, when they're interested in mating, will emit these high-frequency vocalizations, a song, and if the female mouse likes that song, then she will allow that male to mate with her, and so we record their vocalizations,” the researcher explains.

The waveforms produced by active neurons are then recorded by a computer software.

“You can see here that one particular neuron in the female mouse's auditory system responds to one particular vocalization, but when we present a different vocalization, the neuron doesn't respond,” Portfors adds.

“So each individual neuron has an ability to discriminate between different sounds that the male mouse is making in the presence of the female mouse,” the investigator goes on to say.

“We have to try and come up with some ideas of how all the cells get put together and how their inputs create the big wiring pattern that we have in our brains,” she concludes.