生物谷：今天的人类已经高度社会化，但是每次形成新的社会关系的时候，人们都会在心里给对方的可信度打分。美国科学家7月27日在《美国自然人类学杂志》（American Journal of Physical Anthropology）网络版上发表论文称，这种行为是由大脑的类扁桃体结构（amygdala）进化重组造成的。
科学家早已知道，大脑类扁桃体在感受恐惧方面起着关键作用。最近研究又发现，孤独症患者的大脑类扁桃体含有更少的神经细胞，特别是在外侧核（lateral nucleus）区域。
为了弄清不同灵长类动物大脑类扁桃体的差别，在最新的研究中，美国加州大学圣地亚哥分校的人类学家Katerina Semendeferi领导研究小组测量了12具猿和人体标本的大脑类扁桃体尺寸，他们发现，人类大脑类扁桃体比猿的要大得多，并且人类大脑中外侧核在类扁桃体中所占的比例也比猿的高。研究人员表示，虽然外侧核的具体功能尚不清楚，但是它比类扁桃体其它区域与大脑颞叶（temporal lobe）有着更直接的联系，而大脑颞叶则与处理情绪和社交行为有关。
研究小组推测，自从人和猿在进化路上“分道扬镳”后，类扁桃体外侧核便开始变大，而这种变大可能正反映了生活在人类大族群里的社会压力。
美国埃默里大学的人类学家James Rilling表示，该项研究包括了大量的猿类标本，成果显著。但是要想得到确切的结论，即外侧核与高度社会化有关，还需要做更多的研究。下一步的工作就是采用脑成像技术来确认外侧核与颞叶之间的联系。（科学网 梅进/编译）
原始出处:
Research Article
A comparative volumetric analysis of the amygdaloid complex and basolateral division in the human and ape brain
Nicole Barger 1, Lisa Stefanacci 2, Katerina Semendeferi 1 *
1Department of Anthropology, University of California, San Diego, La Jolla, CA 92023
2Salk Institute for Biological Studies, La Jolla, CA 92037
email: Katerina Semendeferi (ksemende@ucsd.edu)
*Correspondence to Katerina Semendeferi, Katerina Semendeferi, Department of Anthropology, University of California, San Diego, 9500 Gilman Drive, 0532, La Jolla, CA 92093-0532
Funded by:
Busch Gardens Zoo (Tampa Bay, FL)
Gladys Porter Zoo (Brownsville, TX)
Oregon Zoo (Portland, OR)
Henry Doorly Zoo (Omaha, NE)
Milwaukee County Zoo (Milwaukee, MI)
Yerkes National Primate Research Center (Atlanta, GA)
Chancellor's Interdisciplinary Collaboratory Scholarship
Kavli Institute for Brain and Mind at the University of California at San Diego
Keywords
brain evolution ?orangutan ?limbic ?comparative neuroanatomy ?morphometry
Abstract
The amygdaloid complex functions to facilitate effective appraisal of the social environment and is an essential component of the neural systems subserving social behavior. Despite its critical role in mediating social interaction, the amygdaloid complex has not attracted the same attention as the isocortex in most evolutionary analyses. We performed a comparative analysis of the amygdaloid complex in the hominoids to address the lack of comparative information available for this structure in the hominoid brain. We demarcated the amygdaloid complex and the three nuclei constituting its basolateral division, the lateral, basal, and accessory basal nuclei, in 12 histological series representing all six hominoid species. The volumes obtained for these areas were subjected to allometric analyses to determine whether any species deviated from expected values based on the other hominoids. Differences between groups were addressed using nonparametric comparisons of means. The human lateral nucleus was larger than predicted for an ape of human brain size and occupied the majority of the basolateral division, whereas the basal nucleus was the largest of the basolateral nuclei in all ape species. In orangutans the amygdala and basolateral division were smaller than in the African apes. While the gorilla had a smaller than predicted lateral nucleus, its basal and accessory basal nuclei were larger than predicted. These differences may reflect volumetric changes occurring in interconnected cortical areas, specifically the temporal lobe and orbitofrontal cortex, which also subserve social behavior and cognition, suggesting that this system may be acted upon in hominoid and hominid evolution. Am J Phys Anthropol, 2007. © 2007 Wiley-Liss, Inc.
