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PNAS u August 21, 2012 u vol. 109 u no. 34 u 13467–13468 www.pnas.org/cgi/doi/10.1073/iti3412109 The brain’s anterior hypothalamus (AH) is associated with neural processes related to aggression and defense, but specific cell types responsible for aggression have not been identified. James Goodson et al. (pp. 13847–13852) show that aggression in finches is promoted in a selective and potent manner by dorsal AH neurons that produce vasoactive intestinal polypeptide (VIP), previously shown to promote territorial aggression in songbirds. The researchers used antisense oligonucleotides to selectively block AH VIP production in male and female violet-eared waxbills, territorial finches that aggressively defend large, exclusive territories. The birds reacted less aggressively than typical waxbills to an intruder, but most continued to respond with a threat or agonistic call within 2 seconds of an intrusion, suggesting that the birds classified intruders as offensive but failed to pursue them. The number of VIP-producing AH cells correlated positively with aggression, and other social and anxiety-like behaviors were not affected. Gregarious zebra finches, which mainly exhibit aggression only in the immediate vicinity of their nests, also showed significant and specific reductions in aggression—primarily nest defense—following AH VIP knockdown. According to the authors, the findings suggest that VIP-producing AH neurons selectively promote offensive aggression in finches. — S.R. Brain cell that promotes aggression