Abstract：
Altruism is a type of prosocial behavior that is carried out in the absence of personal benefit or even at an expense to self. Trait altruism varies greatly across individuals, and the reasons for this variability are still not fully understood. Growing evidence suggests that altruism may be partly determined by the oxytocin receptor (OXTR) gene, which regulates the emotions underlying altruistic attitudes, such as empathy and trust. Neuroimaging and lesion studies have also implied several higher-order brain regions, including the prefrontal cortex, in altruistic behaviors. Yet the existing reports are contradictory and suggest that the top-down control exercised by the prefrontal cortex may promote both altruistic and self-interested behaviors and, thus, could obscure one\'s natural proclivity towards altruism encoded by OXTR. Here, we hypothesized that extensive prefrontal damage would result in an increased influence of the OXTR genotype on one\'s altruistic attitudes and actions. To test this hypothesis, we recruited 115 male combat veterans with penetrating traumatic brain injury to the prefrontal cortex and other brain regions, as well as 35 demographically matched control subjects without brain injury. Participants completed a self-report altruism questionnaire and were genotyped for four OXTR single nucleotide polymorphisms implicated in prosocial behavior, including rs53576, rs1042778, rs2254298 and rs7632287. Consistent with the previous studies, we found that individuals homozygotic for the G allele of rs53576 and rs7632287 were significantly more altruistic than carriers of at least one \"vulnerable\" A allele. Remarkably, in patients with prefrontal cortex damage, greater lesion extent was associated with significantly lower altruism scores in carriers of the A allele of rs7632287, but not in G-homozygotes, suggesting that significant disruption of the prefrontal cortex increased the influence of genetic polymorphisms on prosocial behavior. This study presents the first account of an interaction effect between the OXTR genotype and the location and extent of brain damage.
摘要：
利他主义是一种在没有个人利益甚至牺牲自我的情况下进行的亲社会行为。特质利他主义在个体之间差异很大，这种可变性的原因仍然没有完全理解。越来越多的证据表明，利他主义可能部分由催产素受体（OXTR）基因决定，调节利他态度背后的情绪，比如同理心和信任。神经影像学和病变研究也暗示了几个更高阶的大脑区域，包括前额叶皮层,利他行为。然而，现有的报告是矛盾的，表明前额叶皮层的自上而下的控制可能会促进利他行为和自利行为，因此，可能会掩盖一个人对OXTR编码的利他主义的自然倾向。这里,我们假设广泛的前额叶损伤会导致OXTR基因型对一个人的利他态度和行为的影响增加。为了检验这个假设，我们招募了115名男性退伍军人，他们对前额叶皮层和其他大脑区域进行了穿透性创伤性脑损伤，以及35名没有脑损伤的人口统计学匹配的对照受试者。参与者完成了自我报告利他主义问卷，并对四种涉及亲社会行为的OXTR单核苷酸多态性进行了基因分型，包括rs53576,rs1042778,rs2254298和rs7632287。与以前的研究一致，我们发现rs53576和rs7632287的G等位基因纯合的个体比至少一个“易损”A等位基因的携带者更利他。值得注意的是,在前额叶皮质损伤患者中，在rs7632287的A等位基因携带者中，较大的病变程度与明显较低的利他主义评分相关，但在G纯合子中没有，提示前额叶皮质的显著破坏增加了遗传多态性对亲社会行为的影响。这项研究首次说明了OXTR基因型与脑损伤的位置和程度之间的相互作用。
