The first rule of fight club is “you do not talk about fight club,” but the first rule of mouse fight club seems to be “publish your results in Nature.”
A team of Princeton neuroscientists recently set up a kind of sparring camp for lab mice to find out how watching a fight influenced their behavior. The team split the animals (all males) into three different groups: fighters, spectators, and novices. For the next eight days, each group engaged in a training regimen of sorts. The fighters sparred against a weaker opponent, the spectators watched two other mice fight, and the novices enjoyed a little play session with a mouse-shaped stuffed toy.
Read more: “What Darwin Overlooked About Fighting Female Animals”
Then it was time to get in the octagon. All the experimental mice had to endure three four-minute rounds with an opponent who was no pushover. During the training and fights, god-like entities (okay, the neuroscientists) watched from above, filming their behavior.
Just like us, the team found that mice were enthralled by fights. “The observing mice don’t care so much when the fighting animals were just walking around and interacting,” study author Annegret Falkner explained in a statement. “But we see them orient and attend once attacks start. Even if an attack starts and they’re not oriented, they’re more likely than chance to turn and watch what’s happening, so there’s something very salient and sticky about aggression that’s different from other behaviors.”
Watching the fights seemed to benefit the spectators when it was their turn in the ring. Both the spectators and the fighters were quicker on the attack and less likely to turn their backs than the novices. Interestingly, the time spent attacking was the same for all groups, suggesting that watching and fighting didn’t make those mice any more aggressive than the novices overall.
Of course, organizing a mouse fight club was the entire point of the experiment. The mice were genetically engineered with excitatory neurons that glowed green and inhibitory neurons that glowed red when they fired. To take a peek under the neural hood, the researchers inserted microthin fiber optic filaments into regions of their brains and watched the light show. When they viewed the fights, spectators’ inhibitory neurons fired like a fighter’s, but their excitatory neurons looked more like novice’s.
“They’re kind of midway between the truly experienced fighters and the naive animals,” Falkner said. “There’s something about experience that gets you all the way there, but observation gets you in a similar direction, but only about halfway.”
When spectators fought, however, both patterns resembled the fighter’s. Over the course of eight days, inhibitory cells surrounding aggression hubs eased up in both fighters and spectators. When the researchers tinkered with their neural activity to boost inhibition, these more experienced pugilists suddenly fought like novices again.
And according to the team, it might be possible to run the experiment in reverse. Now that they know what trained fighting neural activity looks like, they may be able to bestow those patterns onto a novice mouse, transforming it into a more skilled combatant.
“If you think about the photometry data as the musical staff of exactly what they just saw, we could replay all that activity back down to the circuit and give them the experience of watching, even though they never watched anything,” Falkner said. “If you replay back this sequence of activity and then you test them, do they behave as if they actually watched a fight?”
So what does that mean for us?
Obviously downloading years of krav maga into our brains isn’t on the immediate horizon, but the findings do suggest that witnessing violence may make us more prepared for it. “I have a hunch that probably some of these circuit changes are conserved in mice and humans,” Falkner said.
Maybe watching kung-fu movies isn’t such a waste of time after all.
Enjoying Nautilus? Subscribe to our free newsletter.
Lead Image: RifqiChandra / Shutterstock
