Doctoral Dissertation Improvement: Brain Size and Shape in Early Anthropoids

现存的灵长类动物--猴子、猿和人类--的大脑比狐猴和懒猴（Strepsirrhini）的大脑大。大小差异集中在某些大脑区域，包括嗅球，新皮层和小脑。这些变化的大小和比例往往强调在讨论中的差异，适应性反应的社会和环境压力之间的蝗虫和strepsirrhines。大脑大小和形状的变化也被用来解释现存灵长类动物头骨形状的一些差异。然而，大多数这些比较分析仅仅是基于对现存灵长类动物大脑的研究。化石证据表明，在灵长类动物的分支之间，大脑大小的平行增长提供了一个宝贵的机会，从比较和历史的角度来测试大脑大小和颅骨组织的发育和空间限制。使用颅骨的微型CT扫描虚拟地呈现内模。这项研究由博士生Kari艾伦在杜克大学的Richard Kay博士的监督下进行，通过检查现存和灭绝的灵长类动物的虚拟内模来探索大脑大小，形状和比例的演变及其与颅骨形状的关系，以确定各种灵长类动物群体在地质时代的趋势。三维几何技术用于表征可能携带功能或系统发育信号的内模形状的全球和区域差异。重建的大小和形状的选定区域的endosts被用来评估小脑，大脑和额叶扩张的时间和它们的关系方面的颅形。古生物学数据集包括来自非洲和南美洲的早期古生物化石，以及欧洲始新世基底灵长类动物。这些新的数据提供了有用的信息，以测试从现存灵长类动物的比较研究中发展出来的关于大脑进化的适应性解释。 本科生培训将纳入研究活动，存档的，免费提供的活体灵长类动物的微型CT扫描将作为教学材料。

Living anthropoid primates - monkeys, apes and humans - have proportionally larger brains than lemurs and lorises (Strepsirrhini). The size differences are concentrated in certain brain regions, including the olfactory bulb, neocortex, and cerebellum. These shifts in size and proportions are often highlighted in discussions of differences in adaptive responses to social and environmental pressures between anthropoids and strepsirrhines. Shifts in brain size and shape also are used to explain some differences in cranial shape among living primates. Most of these comparative analyses, however, are based only on studies of the brain of living primates. Fossil evidence for parallel brain size increase between anthropoid clades provides a valuable opportunity to test developmental and spatial constraints on brain size and cranial organization from both a comparative and historical perspective.Many details of brain size and proportions in extinct primates can be estimated from the size and proportions of endocasts, a cast of the internal braincase. Endocasts are virtually rendered using micro-CT scans of crania. This research, conducted by doctoral student Kari Allen, under supervision by Dr. Richard Kay at Duke University, explores the evolution of brain size, shape, and proportion, and its relationship to cranial form, by examining virtual endocasts of both living and extinct anthropoids to identify trends through geologic time in various primate groups. Three-dimensional geometric techniques are used to characterize global and regional differences in endocast shape that may carry a functional or phylogenetic signal. The reconstructed size and shape of selected regions of the endocasts are used to evaluate the timing of cerebellar, cerebral and frontal lobe expansion and their relationship to aspects of cranial form. The paleontological dataset includes early fossil anthropoids from Africa and South America, and European Eocene basal primates. These new data provide useful information to test adaptive explanations about brain evolution that were developed from comparative studies of living primates. Undergraduate student training will be incorporated into the research activities, and the archived, freely-available micro-CT scans of living primates will serve as teaching materials.