Fighting female fruit flies are helping researchers understand why we stay angry. Credit: Rubin Lab/HHMI Janelia Research Campus
Key points:
- Researchers have identified specific cell types that contribute to a persistent aggressive state in female fruit flies.
- Initially, scientists thought persistent aggression was a result of a recurrent connection, but there may be other factors at play.
- Determining the mechanisms underlying aggression can help scientists better understand aggressive behavior in humans.
Fruit flies experience states of persistent aggression. For female fruit flies, this aggression is a survival mechanism that causes them to headbutt, shove, and fence other female flies to guard prime egg-laying territory.
Now, a study published in eLife characterizes the neurons, circuits, and mechanisms underlying persistent aggression in fruit flies.
Researchers separated female fruit flies with a barrier and then activated different cell types in the brain associated with aggression for 30 seconds at a time. They kept the flies separated for specific periods of time, up to 30 minutes, before removing the barrier.
Activation of the aIPg cell type contributed to persistent aggression such that flies would fight for up to 10 minutes after the barrier was removed. Activating the pC1d cell type, which previously showed involvement in aggression, had no effect.
Initially, scientists thought persistent aggression was a result of a recurrent connection between aggression-associated cells where signals would loop back and feed into the same neural circuit. However, they found that neither cell type—aIPg or pC1d—demonstrated persistent neuronal activity, meaning that the aggressive state does not depend on a recurrent connection between aIPG and pC1d.
These findings suggest that persistent aggression may be regulated by additional factors, including neuromodulators, downstream neurons, and other neural circuits.
Determining the mechanisms underlying aggression can help scientists to better understand aggressive behavior in humans. The basis of these behaviors has implications for neurodegenerative or psychiatric diseases that have comorbid aggression.
“For our society, it’s important to be able to decrease aggression and figure out how to stop persistent aggression,” said study author Katie Schretter of the Howard Hughes Medical Institute. “Figuring out how the circuit works can help us figure out how we might decrease it.”