The multi-stage plasticity in the aggression circuit underlying the winner effect.

Area of Science:

• Neuroscience
• Behavioral Biology
• Aggression Research

Background:

• The "winner effect" describes how winning increases future success and aggression.
• Understanding the neural mechanisms underlying this phenomenon is crucial.

Purpose of the Study:

• To investigate the neural plasticity changes associated with the winner effect over 10 days in male mice.
• To identify the specific brain regions and pathways involved in generalized aggression enhancement.

Main Methods:

• Behavioral assays to measure aggression in male mice after repeated winning.
• Electrophysiological recordings and optogenetics to study neural plasticity in the ventrolateral ventromedial hypothalamus (VMHvl).
• Investigating the role of the posterior amygdala (PA)-VMHvl pathway.

Main Results:

• Winning induced a transition from target-specific to generalized aggression over 10 days.
• Three causally linked plasticity events were observed in VMHvl: potentiation of long-range inputs, strengthened local connectivity, and increased excitability.
• Optogenetic activation of the PA-VMHvl pathway mimicked these plasticity events, while blocking it abolished winning-induced plasticity.

Conclusions:

• Repeated winning triggers a cascade of Hebbian synaptic and excitability plasticity within the VMHvl aggression circuit.
• The PA-VMHvl pathway plays a critical role in mediating the neural changes underlying the winner effect.
• These findings reveal the neurobiological basis for increased aggressiveness in repeated winners.