The evolution of neuronal circuits underlying species-specific behavior

The nervous system is evolutionarily conservative compared to the periphera l appendages that it controls. However, species-specific behaviors may have arisen from very small changes in neuronal circuits. In particular, change s in neuromodulatory systems may allow multifunctional circuits to produce different sets of behaviors in closely related species. Recently, it was de monstrated that even species differences in complex social behavior may be attributed to a change in the promoter region of a single gene regulating a neuromodulatory action.