You
cant call it a dictionary just yet, but University of Delaware
neuroscientist Joshua Neunuebel is starting to break the code mice use
to communicate with each other.
So far, its all action-specific. Mice sound one way when they are
being chased, quite another when they are the chaser, not much at all
when they are not in motion.
He knows this because he and his research team have found a way to
identify precisely which mouse is making which sound, where and when.
Their findings, which were just published in Nature Neuroscience,
provide a foundation for examining the neural circuits that link
sensory cues specifically these ultrasonic mouse calls to social
behavior.
This is fundamental science that will allow us to potentially get at
more complicated problems, Neunuebel said. That includes a broad range
of communication disorders, including autism.
The work is supported by the Foundation for the National Institutes
of Health, the University of Delaware Research Foundation and Delawares
General University Research Program.
Humans cant hear the majority of mouse-to-mouse vocal interactions
at all because they happen on a scale our ears dont catch. This is
likely one of lifes hidden blessings, since mice like to scurry around
in our walls, attics, basements and other human habitats.
But studying their communication patterns can help researchers
understand the neurobiology of social behavior and bring valuable
insightnot just into the secret life of rodents, but possibly into the
mechanics of human communication. Research shows that about 98 percent
of human genes are shared by mice.
To study these mouse interactions, Neunuebels team gathered data as
four mice two males, two females got acquainted. The mice interacted
for five hours at a time in a chamber fitted with eight microphones and
a video camera. Researchers recorded 10 similar encounters using
different mice each time, studying a total of 44 mice.
They collected enormous amounts of data, with each microphone
capturing 250,000 audio samples per second and the video camera
capturing 30 frames per second. Each five-hour encounter produced more
than 100 gigabytes of data.
Using machine-learning programs along with other computational
approaches, they were able to show that specific sounds were associated
with distinct behaviors.
To make sense of the mountain of data, we wrote a lot of computer
programs, Neunuebel said. Everybody in the lab now writes code and
thats a huge attribute of what my lab does. I think its essential for
deciphering very complex behavior.
That code is available free of charge to other interested researchers, he said.
Among their findings:
Mouse calls are different depending on the position of the mouse whether they are chasing or fleeing.
Decreasing pitch was related to dominant signals, while increasing pitch was related to non-dominant behavior.
A significant link was found between certain calls and behavior that followed.
The sounds affect only the mouse who is interacting, not those who are nearby but not involved in the action.
Different situations produced different types of calls.
Another recent study by Neunuebels team drew on the same
microphone/camera setup and showed how specific social interactions
differ.
In that study, published by Scientific Reports, the calls of female mice were analyzed by their interaction with male mice or with other female mice.
They found two new distinctives in this study. First, female mice
almost always vocalize at close range to other mice, while male mice
call out at widely varying distances. Second, female mice vocalize
sooner when in the company of male mice than in the company of other
females.
The team said the most compelling finding of this study was that
mouse behavior changes depending on the vocalizations of other mice. For
example, the male accelerates after a female vocalizes if she is moving
faster than he has been.
Neunuebel said his labs setup where the mice mingle freely is
much more dynamic than more standard approaches that allow animals to
see each other but keep them separated to make it easier to quantify an
animals social behavior.
Here there is free interaction, he said. It is complex and the
mice emit a lot of vocalizations. We know who is vocalizing and we can
see how they all respond to specific types of calls.
That is information that may soon produce much more insight into how a
mouses brain circuitry works the way messages are sent, interpreted
and acted upon.
About the researcher
Joshua Neunuebel is an assistant professor of neuroscience in the Department of Psychological and Brain Sciences. He earned bachelors and masters degrees in
biology at Texas A&M University and his doctorate in neuroscience at
the University of Texas Health Science Center at Houston. He did
postdoctoral fellowships at Johns Hopkins University and Howard Hughes
Medical Institutes Janelia Research Campus, before joining the UD
faculty in 2014.
View a video here about his newest findings,
Article by Beth Miller; video and illustration by Jeffrey C. Chase
Published Feb. 17, 2020
