Allometry, sociality, domestication and the evolution of the vertebrate brain.

不同脊椎动物的大脑在大小和形状上有很大差异，但这种解剖学差异是如何以及为什么存在的，在很大程度上是未知的。我的研究计划通过使用一套神经科学，动物行为和进化生物学方法比较物种内和物种间的大脑解剖来解决这个基本问题。在这个资助周期中，我的研究计划将继续致力于通过追求3个主要目标来确定哪些因素负责在大脑中产生解剖多样性。首先，我将挑战大脑区域总是通过增加神经元而扩展的假设。我将利用我大量的、比较性的大脑样本，测试更大的感觉和运动区域是否是通过神经元的增加、神经元细胞体的扩张或两者兼而有之而进化出来的。我预测，感觉区域的扩大主要是通过增加神经元作为增加感觉受体的结果。相比之下，我预测大脑运动区域的扩张主要是由于神经元大小的增加，而不是增加更多的神经元。这些测试将为神经元数量对大脑解剖学中物种差异的相对重要性提供新的见解。第二，我将测试社会行为的进化是否与大脑的解剖学差异有关。人们认为，记忆和使用社会互动信息的需要是灵长类动物和其他动物大脑扩张的驱动力。然而，对这一理论的实证支持缺乏一个精心设计的测试，在该测试中，特定大脑区域的大小和组成被量化，混淆变量被控制。我将通过比较两个大脑区域的解剖结构来进行这样的测试，前额叶皮层和海马体，在表现出不同程度社会行为的地松鼠物种中各不相同。这将是迄今为止对社会性和大脑解剖学之间关系的最彻底的测试。第三，我将比较不同鸽种的大脑解剖结构，以测试对特定行为或身体特征的选择是否会对大脑解剖结构产生影响。驯化的物种提供了一种独特的方法来测试特定性状选择的效果，这是通过物种比较无法实现的，通过比较品种。我将比较信鸽与其他品种信鸽的大脑解剖结构，以及不同品种信鸽在喙的大小和形状上的触觉和视觉通路。这些品种间的比较将提供一个强有力的和有效的测试，是否选择单独的形态是足以驱动大脑解剖结构的重大变化，或者如果大脑解剖结构的变化只响应于选择的行为。这套独特的跨物种研究将对大脑解剖与行为之间的功能关系产生新的见解，并提高我们对大脑解剖在物种之间和物种内（包括人类）差异的理解。

The brain differs greatly in size and shape across vertebrate species, but how and why this anatomical diversity exists is largely unknown. My research program addresses this fundamental issue by comparing brain anatomy within and across species using a suite of neuroscience, animal behaviour and evolutionary biology methods. Over this grant cycle, my research program will continue to work towards identifying what factors are responsible for generating anatomical diversity in the brain by pursuing 3 main objectives. First, I will challenge the assumption that the brain regions always expand through the addition of neurons. Using my large, comparative brain collection, I will test if larger sensory and motor regions evolve through the addition of neurons, expansion of neuron cell bodies or both. I predict that sensory regions expand primarily through the addition of neurons as a result of an increase in sensory receptors. In contrast, I predict that the expansion of motor regions in the brain arise primarily from increasing neuron sizes, rather than adding more neurons. These tests will provide new insights into the relative importance of neuron numbers to species differences in brain anatomy. Second, I will test if the evolution of social behaviour is associated with anatomical differences in the brain. The need to remember and use information about social interactions is thought to be a driving force for the expansion of the brain in primates and other animals. Empirical support for this theory is, however, lacking a well-designed test in which the size and composition of specific brain regions are quantified and confounding variables are controlled. I will conduct such a test by comparing the anatomy of two brain regions, the prefrontal cortex and hippocampus, vary across ground squirrel species that exhibit different degrees of social behaviour. This will represent the most thorough test of the relationship between sociality and brain anatomy to date. Third, I will compare brain anatomy across pigeon breeds to test if selection for specific behavioural or physical traits has consequences for brain anatomy. Domesticated species offer a unique means of testing for the effects of specific trait selection that cannot be achieved through species comparisons, by comparing breeds. I will compare the brain anatomy of homing pigeons relative to other breeds and the tactile and visual pathways of pigeon breeds that vary dramatically in beak size and shape. These inter-breed comparisons will provide a strong and effective test of whether selection for morphology alone is sufficient to drive major changes in brain anatomy or if brain anatomy only changes in response to selection for behaviour. This unique suite of studies within and across species will yield novel insights into the functional relationships between brain anatomy and behaviour and improve our understanding of why brain anatomy varies among and within species, including humans.