Quantitative analysis of neuronal cells in specific brain areas of different avian orders: Comparison of avian species with high cognitive abilities to species with lower cognitive skills.

据信，灵长类物种拥有动物界中最先进的认知技能。然而，鸟类物种，如一些乌鸦和鹦鹉物种，其认知能力似乎与非人类灵长类动物的技能相匹配。这反映在他们使用工具、进行因果推理和展示未来规划以及想象力的能力上。尽管这些鸟类和非人类灵长类动物的认知能力非常相似，但它们的大脑组织却截然不同。因此，假设高级认知能力可以基于不同的神经元结构是可行的。然而，这提出了一个问题，即在灵长类动物和某些鸟类中，是哪些因素导致了这种特殊大脑的进化，只有这些物种表现出高级认知技能。大脑的绝对大小和相对大小似乎不足以解释脊椎动物认知技能的差异。高级认知功能的进化发展必须依赖于其他因素。最近在灵长类动物中发现了这种可能的因素。灵长类动物的大脑与其他哺乳动物的大脑不同，它们的神经元比例规则允许它们在每脑体积上积累比其他哺乳动物物种更多的神经元。初步数据表明，雀形目鸟类，包括乌鸦，与灵长类动物一样，也有这种比例规则。因此，类似的神经元缩放规则可能是灵长类和鹦鹉高级认知技能之间的联系因素。该项目的目的是量化鸟类不同前脑区域中神经元的数量，以调查这种有利的比例规则是否存在于拥有高级认知技能的鸟类物种中，以及这些比例规则是否特定于特定的大脑区域。出于这个原因，我计划分析已被证明与鸟类高级认知功能相关的大脑区域的细胞组成，例如与主要运动和感觉区域相比的nidopallium/Mesopallium。细胞组成的研究将使用最近发展起来的一种方法：各向同性分馏塔技术。这种方法可以精确测量给定区域内的神经元数量，而不受细胞分布异质性的影响。这项分析将在四种乌鸦和三种鹦鹉以及其他五种没有表现出非凡认知技能的鸟类身上进行。我预计与高级认知能力相关的大脑结构将显示出与其他鸟类相比，乌鸦和鹦鹉物种的细胞密度更高。另一方面，与认知关系较小的区域的细胞密度预计会随着给定物种的运动/感觉特征而变化。如果是这样的话，这项研究将提供对神经元先决条件的第一次洞察，这些先决条件允许在两个不同组织的神经元系统中发展高级认知能力。

It is believed that primate species possess the most advanced cognitive skills in the animal kingdom. However, avian species like some corvid and parrot species show cognitive abilities which seem to match the skills of non-human primates. This is reflected in their capability to use tools, perform causal reasoning and exhibit future planning as well as imagination. Although the cognitive abilities are highly similar between these avian species and non-human primates, their brain organization is vastly different. Therefore, it is feasible to assume that advanced cognitive abilities can be based on different neuronal architectures. This, however, raises the question of which factors have contributed towards the evolution of such specialized brains in both primates and certain avians, that only these species evince advanced cognitive skills. Absolute and relative brain size seem to be insufficient to explain the differences in cognitive skills within vertebrates. Evolutionary development of advanced cognitive functions has to depend on other factors. Such a possible factor has recently been identified in primates. Primate brains differ from other mammalian brains in their neuronal scaling rules allowing them to accumulate more neurons per brain volume than other mammalian species can. Preliminary data indicates that Passeriformes birds, which include corvids, share this scaling rule with primates. Therefore, comparable neuronal scaling rules could be the connecting factor between the advanced cognitive skills in primate and corvids. The aim of the presented project is to quantify the number of neurons in different forebrain areas of birds to investigate if such favorable scaling rules are present in avian species with advanced cognitive skills, and if these scaling rules are specific to certain brain areas. For this reason I plan to analyze cellular composition of brain areas which have been shown to be related to advanced cognitive functions in birds, such as the Nidopallium/Mesopallium in comparison to primarily motor and sensory areas. Cellular compositions will be investigated by using a recently developed method: the Isotropic fractionator technique. This method allows precise measurements of neuron numbers within a given area not affected by heterogeneity in cellular distribution. The analysis will be done in four corvid and three parrot species, as well as five other avian species which do not show extraordinary cognitive skills. I expect that brain structures associated with advanced cognitive abilities will show higher cell densities in corvid and parrot species in contrast to other birds. On the other hand, cellular densities of areas less related to cognition are expected to scale with motor/sensory characteristics of the given species. If this is the case, this study will provide the first insight into the neuronal prerequisites which allow the development of advanced cognitive abilities in two differently organized neuronal systems.