Comparative quantitative analysis of the cellular composition of the prefrontal cortex in the superorder Cetartiodactyla, using DTI and isotropic fractionator technique.

哺乳动物之间的脑大小差异约为100，000倍，绝对脑大小从小于0.1克（食虫动物）到9，000克（抹香鲸）不等。大脑的大小由多种因素决定，例如：神经元的数量，神经胶质细胞的数量，细胞体的大小，树突和轴突分支以及血管和心室系统的大小。通常认为神经元的数量决定了神经元的功能，因此也决定了行为。直到最近，很少有人知道哺乳动物大脑的定量细胞组成，但是随着各向同性分馏器技术的发展，总的神经元和神经胶质细胞的数量已被检查在4个不同的哺乳动物订单日期。与传统观点相反，神经元密度似乎不会随着大脑大小的增加而减少，而是大脑的规模是其神经元数量的特定功能。此外，胶质细胞密度似乎是相对恒定的物种之间的不同的订单，并不增加大脑的大小，因为先前assumed.哺乳动物的总纲Cetartiodactyla是由偶数趾有蹄类动物和鲸目动物，因为他们共享一个单系祖先。鲸偶蹄目包含近300个现存物种，是中型至大型哺乳动物中最多样化的一个目，其大脑和身体大小有很大的变化，使这个总目的物种成为研究大脑缩放规则的理想标本。目前的研究建议的全球目标是研究如何在哺乳动物的神经元和神经胶质细胞的数量的函数的神经元和神经胶质细胞的数量与以前研究的哺乳动物的订单，使用各向同性分馏器技术跨哺乳动物的总目的鲸蹄类的规模。此外，我们感兴趣的是这些细胞是如何组织在不同的结构，特别是前额叶皮层，这将使用MRI/DTI划定。这样的比较分析将深入了解细胞脑缩放规则，这些规则在不同的哺乳动物目之间共享，因此可能从共同的祖先继承和保留，以及哪些规则是不同的，因此可能反映这些目之间的系统发育差异。

Brain size between mammals varies by a factor of approximately 100,000X, with an absolute brain size ranging from less than 0.1g (insectivore) up to 9,000g (sperm whale). The size of the brain is determined by a large variety of factors such as: number of neurons, number of glial cells, cell-body size, dendritic and axonal arborisation as well as by the size of the vascular and ventricular systems. It is often assumed that the neuronal number is determinant for neuronal function and hence for behaviour. Until recently, very little was known about the quantitative cellular composition of mammalian brains; however with the development of the isotropic fractionator techniques the total neuronal and glial number has been examined in 4 different mammalian orders to date. Contrary to the traditional view it seems that the neuronal density does not decrease with increasing brain size, rather the brains scale as order-specific functions of their numbers of neurons. Moreover the glia cell density seems to be relatively constant across species of different orders and does not increase with increasing brain size as was previously assumed.The mammalian superorder Cetartiodactyla is comprised of the even-toed ungulates and the cetaceans, as they share a monophyletic ancestry. Cetartiodactyla contains nearly 300 extant species and is the most diverse order of medium to large bodied mammals, with a large variety in brain and body size, making the species of this superorder the ideal specimens in which to study brain scaling rules. The global aim of the present research proposal is to examine how brain size scales across the mammalian superorder Cetartiodactyl as a function of the numbers of neuronal and glial cells in comparison to the previously examined mammalian orders, using the isotropic fractionator technique. Furthermore we are interested in how these cells are organized in different structures, especially the prefrontal cortex, which will be delineated using MRI/DTI. Such a comparative analysis will give insight into cellular brain scaling rules that are shared between different mammalian orders and therefore might be inherited and retained from a common ancestor and what rules are different and thus might reflect phylogenetic variance across these orders.