We have studied how mating stimuli can be represented, and how differences in pay-offs can lead to changes in representation and decision criteria. We have recently begun to study how such representations interact with the neural machinery of emotion - the brain's limbic system. To do so requires model systems in which the minutiae of these interactions can be observed and manipulated. We now focus on the social behavior of rodents because they have a well-characterized neuroanatomy, are amenable to the manipulation of gene expression, and display interesting natural variation in reproductive behavior.

Individual differences in promoter structure, receptor expression and social behavior in the prairie vole. The prairie vole, Microtus ochrogaster, is a socially monogamous species in which adults form life-long pair-bonds. At least some of the monogamous behaviors that distinguish it from its promiscuous congeners are due to the particular brain regions that express receptors for the hormone vasopressin. We have recently documented a surprising level of naturally occurring variation among prairie vole brains. We find that individual differences in the expression of the vasopressin V1aR receptor are correlated with naturally occurring variation in the non-coding, regulatory region of DNA known as the gene's promoter. Moreover, natural variation in male parental care and the integration of spatial and social memory are correlated with natural variation in some of these brain regions. This work serves as a model for understanding how variation in an individual gene can alter complex social behaviors. We are currently collaborating with Dr. Jerry Wolff, at the University of Memphis, to assess the fitness consequences of variation in V1aR function. This will involve neuroanatomical, behavioral and field studies.

Promoter evolution: macroevolutionary patterns. Species differences in the distribution of neuropeptide receptors such as V1aR may prove to underlie many differences in mammalian mating systems. We hope to weave the various threads of our research together by relating the evolution of V1aR expression profiles in multiple species - prairie voles, singing mice and many other rodents - to the DNA sequences in their promoter regions. This sort of comparative genomics project will be used to identify DNA sequences that may contribute to the locality and intensity of gene expression - properties which define how hormones and other neuromodulators are able to shape the expression and evolution of social behaviors. This project will begin in the spring of 2003.