With an experimental setup worthy of a reality game show, scientists put the balance of healthy mice to the test and discovered new insights into how they use their tails.
The results could inform research into neurogenerative diseases in humans despite our tail-lessness.
Laboratory mice (Mus musculus) provide valuable models for human health and disease due to similarities in their genetics, biology and behaviour. Establishing baseline function in healthy mice can help researchers detect signs of illness in mice serving as models of disease.
Researchers have long known that mice use their tails for balance when crossing narrow platforms. However, until now, it was assumed that mice used their tail primarily as a passive counterweight.
To test tail function in mice, a research group from the Okinawa Institute of Science and Technology in Japan created a narrow platform that would randomly tilt 10-to-30-degrees as a mouse tried to cross it.
“[Mice] have adapted to swiftly cross difficult surfaces like thin branches. Our new setup accounts for this by challenging the mice with narrower surfaces and sudden movements,” says Marylka Yoe Uusisaari, leader of the unit and senior author on the study.
Uusisaari’s team used a neural network to track the relative positions of a mouse’s feet, pelvis and tail as it crossed the platform. When the platform suddenly tilted, the neural network consistently showed that mice rapidly rotate their tail in the opposite direction of the tilt, an example of active balancing.
“It would be like if you could swing a whip fast enough to pull yourself in the direction of the crack to avoid falling backwards,” says Salvatore Lacava, first author of the study.
Unlike static platforms, this new experimental setup challenges healthy mice. Meanwhile, the neural network allows researchers to refine the definition of “balanced” to mean that a mouse has its feet beneath its body.
The research team asserts that better understanding of the tail as well as the new experimental setup will allow future researchers to detect nuanced changes in balance for mice modelling neurogenerative diseases.
“We want to be able to spot and treat balancing issues in humans before they become so severe that the patient struggles to walk in a straight line,” says Lacava. “With this study, we have now set the same standard for the mice.”
The research is published in the Journal of Experimental Biology.
