社会与工程心理学研究室知识库

正义或公平是人类社会的重要议题，更具体的说，是人类生活的基本价值观。公平作为一种行为规范，对个人与社会都意义重大。每个人时常都面对着公平与不公平的选择。人们在面对不公平时的反应既表现在接受或拒绝的行为层面上，也表现在包括情绪、认知这类心理反应能力上，而情绪、认知等又体现在脑激活水平或脑网络上。围绕着公平，已有大量的研究使用最后通牒博弈任务范式（Ultimatum Game ，UG）探索了人们面对不公平分配时的行为反应，并借助功能磁共振影像寻找与之相关的大脑基础，且研究成果丰富。但其遗传基础并不清晰，同时能够反应情绪、认知能力的公平特质的神经基础、遗传基础的研究也甚少。全面、深入地探究、解释面对不公平个体差异产生的生理基础，是我们开展此研究的初衷。

为了实现该目标，本研究生学位论文基于单核苷酸多态性 (single nucleotide polymorphism，SNP)的遗传关联分析、神经影像学等方法，通过开展四个研究，探索了遗传因素即基因，公平特质和公平决策行为，公平的静息态连接功能基础三者之间的关系，意图发现三者间的相互作用关系，全面解析个体在面对不公平时个体差异的遗传及神经基础。

研究一采用基于单核苷酸多态性遗传关联分析的方法，探索包括多巴胺与5-羟色胺系统在内的多个候选基因多态性是否会对公平特质，即受害者敏感性，以及公平行为，即在最后通牒博弈任务中回应者拒绝率，造成影响。结果发现：COMT (rs4680)（多巴胺能系统基因）的基因多态性具有能够显著影响个体在受害者敏感性上表现的趋势；HTR2A (rs6311)（5-羟色胺能系统基因）的基因多态性具有能够显著影响被试在最后通牒博弈任务中表现的趋势。这提示我们，特定系统的特定基因能够对公平特质与行为产生影响。

研究二则利用静息态功能磁共振成像技术，基于大脑网络自发的波动，分别以左、右侧背侧脑岛和左、右侧背外侧前额叶为种子点进行静息态功能连接分析，探究公平特质与公平行为在脑中的表征。研究发现，无论对于公平特质来还是最后通牒博弈中回应者行为，均具有其静息态神经基础，其中右侧背侧脑岛与右侧中央前回及中央后回的静息态功能连接与受害者敏感性分数呈现显著的负相关；右侧背外侧前额叶与右侧额下回、岛盖部额下回的静息态功能连接与一般不公平条件下的拒绝率之间呈显著负相关。

在研究一与研究二的基础上，研究3意图探索上述影响公平特质或行为的候选基因多态性与静息态脑功能连接的关系。同样采用基于单核苷酸多态性遗传关联分析的方法，研究发现：年龄能够调节COMT 基因多态性与受害者敏感性相关的静息态脑网络即右侧背侧脑岛与右侧中央前回及中央后回的静息态功能连接的关系；性别能够调节HTR2A 基因多态性与最后通牒博弈行为相关的静息态脑网络即右侧背侧前额叶与右侧额下回、岛盖部额下回的功能连接的关系。

在研究三基础上，研究四采用中介分析，试图发现静息态功能连接在基因与公平特质或行为关系中的中介作用，建立“基因-脑-行为”的关联。分析未发现显著中介作用，但提示年龄对公平特质相关静息态功能连接的中介作用的调节趋势，以及性别对公平行为相关静息态功能连接的中介作用的调节趋势。

总结来说，本研究从遗传基础，到影像学数据，再到行为数据，逐层逐步地深入探索与揭示公平特质与行为个体差异的生理基础。本研究发现单个候选基因多态性具有影响公平特质或行为个体差异的趋势，并影响与公平特质或行为相关的静息态功能连接，但未发现静息态功能连接在基因与公平特质与行为关系中的中介作用。本文所得发现鼓励研究者进一步探索基因-脑-公平特质或行为三者间的关系，以建立稳固的、具体的微观与宏观之间的桥梁。

Justice or fairness is an important issue of human society, more specifically, the basic values of human life. As a code of conduct, fairness is of great significance to both individuals and society. People are confronted with options that are fair and unfair. People's response in the face of unfairness is not only presented on the behavioral level of acceptance or rejection, but also on the psychological response ability including emotion and cognition, which are reflected in the level of brain activation or brain network. Around fairness, a large number of studies with rich research results have adopted the Ultimatum Game (UG) paradigm to study individuals’ response to unfair treatments and its underlying neural mechanisms with the help of function Magnetic Resource Imaging (fMRI) technique. However, the genetic basis of individuals’ reactions towards unfairness is still not clear, and further， there are few researches on the neural basis and genetic basis underlying the emotion and cognitive ability of the fairness. It is our original intention to explore and explain the physiological basis of individual differences towards unfairness comprehensively and deeply.

To achieve this goal, methodologically, this dissertation incorporated genetic association analysis which is based on single nucleotide polymorphism (SNP), neuroimaging and other methods. The current study explored the association among the genetic factors of fairness, fairness-related trait, decision-making behavior and restingstate functional connectivity via four substudies. By demonstrating the associations of these constructs, we intended to comprehensively explored the genetic and neural basis of why individuals react differently in the face of unfairness.

In Study 1, using genetic association analysis of single nucleotide polymorphisms, we explored whether multiple candidate gene polymorphisms, including genes of dopamine and serotonin systems, would affect fairness traits, namely victim sensitivity, and fairness behaviors, namely rejection rate of responders in the UG task. Results showed that COMT (rs4680) (the dopaminergic system gene) had a tendency to affect the individuals' sensitivity to the unfairness as victims. The HTR2A (rs6311) (serotoninergic system gene) had a tendency to affect rejection rate in the UG task. This implied that specific genes in specific systems can influence fairness traits and behaviors.

In Study 2, based on the spontaneous fluctuation of the brain network, the left and

right dorsal insula and dorsolateral prefrontal cortex were used as the seed regions for resting-state functional connectivity to explore the representation of fairness-related trait and behavior in the brain. It is found that victim sensitivity and rejection rate towards unfair offers in the ultimatum game were both associated with certain neural connectivity in the resting state. Specifically, the resting functional connectivity between the right dorsal insula and the precentral and postcentral central gyrus was significantly negatively correlated with the victim's sensitivity. The resting functional connectivity between the right dorsolateral prefrontal gyrus and the right inferior frontal gyrus was significantly negatively correlated with the rejection rate under moderate unfair conditions.

On the basis of first two studies, the Study 3 aimed to investigate the association between the polymorphisms of candidate genes that affect fairness-related trait, behavior and resting-state functional connectivities. Using the same method genetic association analysis as in the first two studies, results showed that: age moderated the relationship between COMT (rs4680) and the neural correlates of victim sensitivity. Gender moderated the relationship between HTR2A (rs6311) and the neural correlates of fairness behavior in UG.

On the basis of the Study 3, Study 4 used mediation analysis to investigate the the mediating role of resting-state functional connectivity in the relationship between genes and behaviors. However, no significant mediation effects were found in Study 4. However, non-significant results suggested a potential inclination of a moderating effect of age on the mediating role of connectivity related to fairness trait in the relationship between genes and trait, and the moderating effect of gender on the the mediating role of connectivity related to fairness behavior in the relationship between genes and behavior.

In conclusion, from genes to imaging data and behavioral data, the current study explored and revealed the physiological basis of fairness-related trait and behavor step by step. We found that the polymorphism of a single gene had a tendency to affect the fairness-related trait or behavior in the UG, and the resting-state functional connectivity corresponding to these trait or behaviors, but no mediating effect of resting-state functional connectivity was found. The results of this research still encourage us to continue to explore the relationships among genes, brain and behaviors until a solid and concrete bridge between micro and macro variables are built up.