Establishing regional specificity of neuroestrogen action

•Neuroestrogens are synthesized by aromatase in the songbird brain.•Neuroestrogen actions are locally regulated in the brain.•The songbird brain balances peripheral and central androgens and estrogens.

The specificity of estrogen signaling in brain is defined at one level by the types and distributions of receptor molecules that are activated by estrogens. At another level, as our understanding of the neurobiology of the estrogen synthetic enzyme aromatase has grown, questions have emerged as to how neuroactive estrogens reach specific target receptors in functionally relevant concentrations. Here we explore the spatial specificity of neuroestrogen signaling with a focus on studies of songbirds to provide perspective on some as-yet unresolved questions. Studies conducted in both male and female songbirds have helped to clarify these interesting facets of neuroestrogen physiology.