Neuromolecular mechanisms of social cognition in a cichlid fish

When interacting with conspecifics, individuals make decisions that integrate, in real-time, the behavior of their social partners with stored experiences from past interactions (learning and memory) and predictions of future behavior. This ability can be referred to as social cognition, defined as awareness of and knowledge about conspecifics, and measured by examining an individual’s perception of and insight into its own and others’ social interactions and relationships. The study of social cognition depends critically on understanding how the brain processes social information. However, the neural and molecular substrates subserving these processes are only poorly understood. To begin to address this knowledge gap, I conducted a series of experiments using territorial male African cichlid fish, Astatotilapia burtoni. I focused on three brain regions critical to social decision-making in vertebrates: the preoptic area and homologs of the amygdala and hippocampus. In Chapter 1, I examined the mechanisms underlying same-sex pair bonding in the context of the Dear Enemy effect and identified a role for the oxytocin receptor homolog in the amygdala and hippocampus. In Chapter 2, I studied the hormonal processes of the Dear Enemy effect as males gained familiarity. Then, I demonstrated that Dear Enemy males will engage in cooperative defense against an intruder. I identified neural correlates of cooperative behavior in the amygdala and preoptic area, as well as within dopaminergic neuron populations. In Chapter 3, I manipulated social context during territory defense to examine how the brain responds to the social environment. I found that blocking D2 dopamine receptors inhibits territory defense in the context of a reproductive opportunity, but not in the context of cooperative defense. Further, I identified differences between social contexts in candidate gene expression levels in the preoptic area. In summary, my data offer novel insight into the neuromolecular mechanisms underlying social cognition in a cichlid fish and suggest several directions for future study.