How does the brain control aggression?
Aggressive behavior in Drosophila melanogaster is sexually dimorphic: males fight by lunging whereas females fight by head-butting. The sexually dimorphic attacks are understandably controlled by distinctive neurons in the brains of the two sexes. But how about the aggressive drive? I reasoned that the aggressive drive is a sexually shared internal state and thus should be similarly controlled in males and females despite of the differences in their behavioral expressions.
I started by testing the neurons that have been shown to promote male aggression to see whether any of them could promote female aggression. I identified a pair of neurons (CAP) that controls the aggressive approach- the appetitive/motivational phase of aggression in males and females. CAP neurons activate the sexually dimorphic downstream neurons, MAP in males and fpC1 in females, to promote sexually dimorphic attacks- the consummatory phase of aggression. I further showed that the CAP-MAP/fpC1 connection is strengthened by social isolation, which is known to increase aggression of both sexes.
The work constitutes one of the first cases that aggression in both sexes can be controlled by a shared, genetically-identifiable cell type (CAP) and that the appetitive and the consummatory phase of aggression can be controlled by the distinct cell types (CAP vs MPA/fpC1). The circuit motif also allows further research on how male and female aggression are modulated by extrinsic and intrinsic factors.
A single pair of neurons. Can you believe it?
A pair of descending neurons of Drosophila melanogaster. The neuronal processes of these neurons cover the entire nervous system including the brain and the ventral nerve cord.
What do these neurons do? !