Functional connectivity among limbic brain areas: Differential effects of incubation temperature and gonadal sex in the leopard gecko, Eublepharis macularius

The neural basis of individual differences in behavior has been studied pri marily by analyzing the properties of specific neural areas. However, becau se of the organization of the nervous system, it is also plausible that dif ferences in behavior are mediated by differences in the interactivity or fu nctional connectivity among brain nuclei in particular neural circuits. In the leopard gecko, Eublepharis macularius, the temperature of the egg durin g incubation not only determines gonadal sex, but also shapes the sociosexu al behaviors, reproductive physiology, and hormone sensitivity of adult ani mals. In this study the effects of both incubation temperature and gonadal sex on functional connectivity among limbic brain areas were examined. Func tional connectivity was assessed by analyzing covariance patterns in metabo lic capacity, as revealed by quantitative cytochrome oxidase histochemistry . It was hypothesized that incubation temperature and gonadal sex affect th e propensity to display aggressive or sexual behaviors by altering the func tional connectivity within relevant neural circuits. The correlations of me tabolic capacity between the anterior hypo-thalamus and both the septum and preoptic area were significant only in relatively aggressive individuals, suggesting that these circuits may regulate the phenotypic variation in agg ressiveness caused by incubation temperature. The correlations between the ventromedial hypothalamus and both the dorsal ventricular ridge and septum were significant only in females, suggesting that these circuits may modula te female-typical sexual behaviors. Correlations among preoptic, hypothalam ic and amygdalar areas tended to be distributed across both sexes, suggesti ng that there may be shared pathways underlying the expression of male-typi cal and female-typical behaviors. Copyright (C) 2000 S. Karger AG. Basel.