Princeton: male mice that only watched fights attacked faster in later combat
In a Princeton study on mice, males that merely watched fights later attacked an opponent faster, and inhibitory neurons in their brains loosened control over aggression centers.
A team at Princeton University led by first author Jorge Iravedra-García reports in Nature that male mice which only watched other mice fight were better prepared for a fight of their own later. spektrum.de describes the work, led by Annegret Falkner spektrum.de
spektrum.despektrum.deOpen source ↗. The authors link the effect to changes in brain activity
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The study builds on an observation in macaques, which pay more attention to videos of fighting conspecifics than to videos of peaceful scenes spektrum.de
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Experimental design
The researchers assigned male mice to one of three groups: fighters, observers or controls. For eight consecutive days, each group took part in three ten-minute behavioral sessions daily spektrum.de
spektrum.despektrum.deOpen source ↗. Fighters sparred with a mouse that was easy to beat. Observers sat on a raised platform and watched a pair of mice fighting below. Controls played with a stuffed toy mouse
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On the ninth day, all animals faced an opponent that was hard to beat, and everything was recorded on video spektrum.de
spektrum.despektrum.deOpen source ↗. According to Falkner, the observing mice were not much interested when the fighting animals only walked around and interacted, but became attentive as soon as attacks began
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During the fight, both observers and fighters attacked the opponent faster and spent less time with their backs turned to it than mice with no prior experience spektrum.de
spektrum.despektrum.deOpen source ↗. The authors interpret this as a "be ready" strategy, that is, proactive aggressive behavior
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Brain activity
To record neural signals in living mice, the team used optogenetic methods. They measured activity in a subcortical network associated with social behavior spektrum.de
spektrum.despektrum.deOpen source ↗. Over the eight days, inhibitory neurons in both fighters and observers gradually loosened their hold on key aggression centers, as if a brake were being released
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When the researchers restored this inhibition, observers behaved like control mice during the fight spektrum.de
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It remains unclear whether the results transfer to humans. According to the authors, the data may help clarify the neural mechanism by which experiences of violence can lead to long-lasting maladaptive behavior spektrum.de
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