健康与遗传心理学研究室知识库

近些年来压力相关的研究问题越来越多地引起人们的兴趣和关注。而对于压力的行为学和神经机制方面的研究因为压力对动物（包括人类）的健康方面的巨大影响而变得非常重要。在人类社会或其他社会性动物群体中，尤其是在非人灵长类动物群体中，来自社会等级的压力被认为对健康有着负面影响。处于不同社会等级地位的个体可能承受着不同程度的压力。为了探讨处于特殊地位的个体在群体中所承受的压力来源及其适应压力的方式，本硕士论文从行为学的角度，以食蟹猴和恒河猴两个非人灵长类群体作为研究对象，分别研究和探讨了（1）处于群体社会中特殊地位（中层地位）的个体压力产生的主要来源，以及处于该地位的个体如何适应其由特殊社会地位所带来的压力；（2）各种不同且具体的社会行为与群体中不同社会等级个体压力状态的相关关系。
在本硕士论文研究一中，我们研究了七个笼养食蟹猴全雄群体中处于第二等级地位的个体，观察并分析了研究对象与同一群体中其他个体的社会接触——如攻击、避让、梳理以及骑跨等社会行为。根据研究结果我们认为来自更高社会等级的个体的攻击是中层等级个体所承受压力的主要来源。但另一方面，这些处于中层等级的个体会通过一些社会行为来帮助缓解自身的等级压力以更好地适应其所属的中层社会等级地位。这些社会行为包括：在被更高等级的个体攻击后马上转向攻击较低等级地位的个体；对较低等级的个体进行更多的攻击；主动避让高等级个体或被较低等级个体避让；为高等级个体梳理毛发或与较低等级个体互相梳理；以及与其他个体间的骑跨与被骑跨等。
为了更具体地探讨社会行为对于处在不同社会等级地位个体的压力状况的影响以及调节作用，在本硕士论文研究二中，我们在研究一的基础上将各种社会行为更具体地区分子类别（如攻击行为被分为极端攻击和温和攻击等），从而对三个笼养恒河猴全雄群体的社会行为做了更加细致的观察和分析。同时，我们对所有研究个体的毛发可的松含量进行了测试，并将个体的毛发可的松水平作为衡量个体压力状况的生理指标。统计分析结果显示，个体的社会地位与毛发可的松的水平（压力水平）呈显著负相关关系（r=-0.52，p=0.036）。从行为学的角度，温和攻击行为的频率与可的松水平呈显著负相关（r=-0.53，p=0.037）；受到极端攻击以及屈服行为的频率与可的松水平显著正相关（r=0.51，p=0.044；r=0.53，p=0.035）。如果将群体分为高、低两个等级子群体，则低等级地位的个体全部亲和行为的总时间与可的松水平呈显著正相关（ r=-0.64 ， p=0.044 ； r=-0.66 ，p=0.036）。这些定量的分析结果说明（并亦在研究一的基础上补充说明）：处于低等级地位的个体较之于高等级地位的个体具有更高的压力水平；个体被攻击以及屈服于冲突较高的频率会导致压力水平升高，同时，一些主动攻击行为会减缓压力；相对低等级地位的个体需要更多的亲和行为来适应并缓解其所具有的高压力状态。
另外，在进行社会行为学研究的同时，我们开发了一套新的与核磁共振扫描仪相容的立体定位-液压微推系统，这个系统可以实时地在非人灵长类个体脑内定位一个或者多个目标脑区并在目标脑区中埋置硅管，因而从方法学的角度为今后的压力相关神经机制的探索提供了一个可靠有效的研究平台。这一方法学的研究将作为附录列在本硕士论文正文之后。

Stress relevant issues are attracting increased interest and attention recently. Research of behavioral and neural mechanisms of stress is very important because of the great impact of stress on health in animals including humans. In this thesis, we targeted non-human primates (cynomolgus and rhesus monkeys) as our subjects, and conducted two related research from the behavioral point of view: (1) Stress-relevant social behavioral study of middle-class male cynomolgus monkeys; (2) study of relationships between various kinds of social behaviors and stress levels of individuals holding different social status in rhesus monkeys. We wish that both studies could provide contributions to better understand on behavior-stress association under the general topic of “stress and health”.
Stress from dominates rank in a human society, or that of other social animals, especially non-human primates, is found to have negative influence on health conditions. And individuals holding different social status may carry various stress levels. The middle-class is considered to be in a special stress situation within the dominant hierarchy because of its situation that being in the ‘middle’ between the higher and lower ones. Behaviorally, questions about either where the mid-class stress comes from, or how the individuals adapt to their mid-class stress remain barely understood in the non-human primates. In study one of this thesis, we observed and analyzed the social interactions, including aggression, avoidance, grooming, and mounting behaviors, between the beta males and their group members that holding either higher or lower social status in seven captive male-only cynomolgus monkey groups. We suggest that aggressive tension from the higher hierarchy members could be the main origin of the stress for the mid-class individuals—beta males in our study. However, behaviors as attacking the lower hierarchy members immediately after being attacked, and conducting more aggressions, as well as receiving and providing avoidance, grooming, and mounting to group members of either higher or lower hierarchy would help with alleviating
their mid-class stress and adapting the particular middle social status.
Based on study one, in order to have a better understanding of how social behaviors affect and regulate stress levels of individuals holding different social status, in study two of this thesis, we categorized various social behaviors into more detailed categories (for example, aggressive behavior was sub-categorized into extreme aggression and mild aggression), and then we observed, recorded, and analyzed these social behaviors of three captive male only rhesus monkey groups. Also, we collected hair samples of all the monkey subjects, and measured hair cortisol concentration, which was used as physiological indicator of stress level of each individual. The statistical results showed that hair cortisol concentration (stress level) was significantly negatively (r=-0.52，p=0.036) correlated with social status. Behaviorally, the hair cortisol concentration was negatively correlated (r=-0.53，p=0.037) with frequency of mild aggression, and positively correlated (r=0.51，p=0.044；r=0.53，p=0.035) with frequencies of extreme submission and receipt of extreme aggression. We further divided the whole group of subjects into high and low ranking sub-groups, and the hair cortisol concentration was positively associated (r=-0.64 ， p=0.044 ； r=-0.66 ， p=0.036) with total duration of all affinitive behaviors in the low ranking group. We suggested that individuals holding lower social status had higher stress levels, and high rates of extreme submission and receipt of extreme aggression might increase stress level. Also, initiating mild aggression might help release social stress, and individuals holding lower ranking social status may need long duration of affinitive behaviors in order to alleviate their relatively high stress level.
Besides, as for future investigation of neural basis of “stress and health”, while conducting the two main studies of this thesis, we also developed a stereotaxicmicrodrive system that is MRI compatible. Using real-time localization with a 7 Tesla MRI scanner, we precisely and efficiently localized target brain areas and surgically implanted an MRI-compatible silicon cannula in rhesus monkey brains. Details of the new method would be explained as appendix in this thesis.