Social behaviour: can it change the brain?

Dominance hierarchies are ubiquitous in social species. Social status is established initially through physical conflict between individuals and then communicated directly by a variety of signals. Social interactions depend critically on the relative social status of those interacting. But how do individuals acquire the information they need to modulate their behaviour and how do they use that information to decide what to do? What brain mechanisms might underlie such animal cognition? Using a particularly suitable fish model system that depends on complex social interactions, we report how the social context of behaviour shapes the brain and, in turn, alters the behaviour of animals as they interact. Animals observe social interactions carefully to gather information vicariously that then guides their future behaviour. Social opportunities produce rapid changes in gene expression in key nuclei in the brain and these genomic responses may prepare the individual to modify its behaviour to move into a different social niche. Both social success and failure produce changes in neuronal cell size and connectivity in key nuclei. Understanding mechanisms through which social information is transduced into cellular and molecular changes will provide a deeper understanding of the brain systems responsible for animal cognition.