Dissertation Research: Structural Differences in the Corpus Callosum of Macaca fascicularis and Pan Troglodytes by Confocal Microscopy

这是对大脑中作为两个大脑半球之间主要交流通道的胼胝体的性别差异的研究。这项研究将使用激光扫描共聚焦显微镜检查两种高等灵长类动物的大脑，食猴（Macaca fascicularis）和普通黑猩猩（Pan troglodytes），这是显微镜成像的最新进展，允许以前无法获得的调查和分析水平。该项目的数据将为非人类灵长类动物胼胝体的基本生物学提供新的信息，并为重建灵长类动物大脑性别差异的进化提供基础。例如，这项研究的发现可能直接与观察到的旧大陆猴子和类人猿中存在的男女认知和/或语言差异有关。拟议的研究将通过测试假设来解决这些说法，即在与总和局部胼胝体区域相关的大体形态学上，以及在有髓和无髓神经纤维的数量上，Macaca fascularis和Pan troglodytes的胼胝体存在性别差异。对纤维成分的了解可以揭示两个大脑半球相互沟通的能力，以及这种沟通可能发生的速度。例如，穿过胼胝体的纤维数量将反映半球之间的连接程度，并提供对功能侧化（即左右区隔）的见解。通过胼胝体的髓鞘纤维（即那些被髓鞘包围的神经纤维，有助于传导速度）的大小，可以深入了解信息在两个半球之间传递的速度。一般来说，神经纤维的直径越大，信号传递的速度就越快。在非人类灵长类动物大脑的一个很大程度上未被探索的区域解决这些基本问题的能力，将为人类大脑中的性别差异是如何产生的提供重要的新信息。

This is an investigation of sexual differences in that part of the brain which serves as the major communicating highway between the two cerebral hemispheres, the corpus callosum. This study will examine the brains of two species of higher primates, the cynomolgus monkey (Macaca fascicularis) and the common chimpanzee (Pan troglodytes) using laser scanning confocal microscopy, a recent advancement in microscopic imaging that allows for a level of investigation and analysis not available previously. Data from this project will offer new information on both the basic biology of the nonhuman primate corpus callosum and provide a substrate which will enable reconstruction of the evolution of sex differences in the primate brain. For example, findings from this study may directly relate to observations on the existence of male-female cognitive and/or linguistic differences in Old World monkeys and great apes. The proposed research will address these claims by testing the hypothesis that sex differences in the corpus callosum of Macaca fascicularis and Pan troglodytes are present in gross morphology related to total and regional callosal areas, and also with regard to the number of myelinated and unmyelinated nerve fibers. Knowledge about fiber composition can shed light on the ability of the two cerebral hemispheres to communicate with each other, and the speed at which this communication may occur. For example, the quantity of fibers traversing the corpus callosum will reflect the degree of connectivity between the hemispheres, and offer insight into the lateralization (i.e., left-right compartmentalization) of functions. The size of the myelinated fibers (i.e., those nerve fibers surrounded by a myelin sheath which aids in conduction velocity) which pass through the corpus callosum will offer insight into the speed at which messages are passed between the hemispheres. In general, the larger the diameter of the nerve fiber the faster the signal will be conducted. The ability to address these fundamental questions on a largely unexplored region of the nonhuman primate brain will offer significant new information on how sexual differences in the human brain came to be.