Abstract
Aggression evolved to protect resources such as food from competitors, but animals must balance fighting and feeding so that they facilitate rather than hinder re-establishment of energy homeostasis. How this balancing is computed is not well understood. We have approached this problem at the level of neural population-coding by examining the effect of progressive starvation on a hypothalamic line attractor that encodes an internal state of aggressiveness. Moderate fasting yielded "hangry" mice, decreasing attack latency and increasing attack frequency. In parallel, line attractor ramping rate and stability were increased, suggesting that hunger enhances aggressiveness by modifying neural dynamics. In contrast, prolonged starvation inhibited aggression and eliminated the line attractor. In satiated mice, titrated acute chemogenetic activation of arcuate AgRP neurons recapitulated the biphasic effects of progressive starvation, suggesting that a continuous increase in hunger exerts bi-directional influences at different intensities. When confronted with food and an intruder, hangry mice alternated between feeding and fighting. During eating, population neural activity moved out of the line attractor while activity in the attractor dimension remained unchanged. Following feeding, activity rapidly relaxed back into the attractor and aggression resumed. Thus, the line attractor may serve to keep hungry animals primed for aggression during intermittent feeding bouts.