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A new tracking system allows researchers to pinpoint which of four mice is ‘talking’ as they mingle freely in a cage. The setup, presented Tuesday at the 2013 Society for Neuroscience annual meeting in San Diego, shows that male mice don’t do all the talking, as was previously thought
The system may be particularly useful for studying autism, which is characterized by problems with communication and language.
Males are known to vocalize in the presence of females, and pups do so when separated from their mothers. Scientists have charted the frequency and length of these cries, building a possible ‘alphabet’ of sounds.
But one important link has been missing. “We’ve never been able to say which mouse was which,” notes Joshua Neunuebel, a research specialist in Roian Egnor’s lab at the Howard Hughes Medical Institute in Ashburn, Virginia, who presented the work. Until now, that is.
The new system allows researchers to place multiple mice in a cage, track and follow each mouse and catalog the interactions between them. Four microphones, placed one on each side of the cage, pinpoint the source of each cry, although it is still difficult to do when the mice are facing each other nose to nose, says Neunuebel.
The researchers used the system to look at interactions between four mice — two males and two females, all of which were either controls or models for fragile X syndrome. They recorded the mice for five hours at a time, seven times with each mouse strain, and were able to accurately identify more than 4,000 cries.
As expected, the male mice vocalize most of the time — about 80 percent. But they found that, unexpectedly, the females answer. What’s more, these cries cluster together, suggesting a call-and-response pattern.
Neunuebel then looked at what the mice were doing at the time of each of the cries. Males and females both cry most often as they approach each other.
“This sounds a lot like a chase, which is a form of courtship in mice,” he says.
Overall, the fragile X mice vocalize under the same social circumstances as the controls do, albeit less often.
Neunuebel plans to test whether the mutant mice follow the same social hierarchy as controls. He says he also wants to assess whether males and females make different types of cries. “There are so many cool things we can do with this.”
For more reports from the 2013 Society for Neuroscience annual meeting, please click here.