Brain mediation of Anolis social dominance displays 1. Differential basal ganglia activation

Ritualistic displays of aggressive intent are important social signals, oft en obviating physically dangerous engagement. To date, however, brain regio ns mediating such behaviors are not established. Here we used male Anolis c arolinensis together with an in vivo C-14-2-deoxyglucose method to determin e patterns of brain activation during elicitation of this animal's dominanc e displays vs. other behaviors. By patching one eye regional brain activati on in the hemisphere receiving display-evocative visual stimuli ('seeing' s ide) was compared to activity in the contralateral brain that did not see s pecific stimuli ('patched' side); this was quantitated as the ratio of seei ng/patched activity for brain regions of interest. Lone males displaying do minantly to mirrors activated dorsolateral basal ganglia (BG) in the seeing , compared to the patched hemisphere; this was not seen in various non-disp laying controls. Degree of dorsolateral BG activation also correlated with a measure of dominant display activity, but not with locomotion. In sociall y stable pairs, displaying dominants showed similar activation of dorsolate ral BG, but deactivated ventromedial BG; non-dominant cagemates displaying submissively had the opposite pattern. When cohabiting peacefully without d isplaying, paired dominants' and subordinates' brain activity patterns were similar to each other. Thus, different BG subsystems seem involved in domi nant vs. submissive display behaviors. Given similarities in both social di splays and BG organization, homologous brain systems might have similar fun ctions in members of other amniote classes, including primates. Copyright ( C) 2001 S. Karger AG, Basel.