Finite Element Analyses of the Mammalian Skull: The Impact of Biting Behavior

哺乳动物的咬入方式与摄食生物力学。放大图片作者：Ian R.马萨诸塞州大学，阿默斯特格罗斯（合作PI）哺乳动物的进化史在很大程度上是一个关于开发越来越广泛的食物资源的故事。虽然第一批哺乳动物是以昆虫为食，但现代哺乳动物的饮食范围从昆虫到水果，树叶，肉类和浮游生物。这种饮食的多样性反映在头骨的形状上-哺乳动物用来咬和咀嚼食物的主要“工具”。然而，重要的是，驱动这种多样性进化的潜在机制尚不清楚。这项研究探讨了生物力学的重要性之间的联系，在咬和哺乳动物头骨的解剖结构，安全和最佳地承担和分散这些力量。 此外，这项研究调查的作用，这种关系在头骨形状的多样性的演变。以前的哺乳动物喂养的分析采取了两种方法，其中每一种都有固有的局限性。广泛的比较研究记录了头骨形状和饮食之间的相关性，但没有测试相关性背后的因果机制。另一方面，详细的实验研究记录了骨骼和肌肉在进食过程中的行为，但实验条件往往与自然条件相去甚远。这项研究将是第一个联合收割机数据的咬合行为和咬合力收集在现场进行的生物力学实验在实验室进行的第一个目的是调查如何不同的咬合方式施加负载到头骨和这些负载是如何分散。常规的咬行为和形态之间的因果关系将通过比较物种内不同的咬风格施加的负载制度。第二个目标是解决哺乳动物进食方面的另外两个未解决的问题：头骨形状受到其他感觉系统（在这种情况下，视觉）限制的程度，以及面部骨骼相对于进食过程中产生的力的强度。这些问题的答案可以解释为什么某些哺乳动物谱系比其他谱系表现出更广泛的头骨形状。 最初，将测量由咬合产生的力，并在现场记录哺乳动物的进食行为。接下来，这些行为的机械影响将在实验室中使用有限元（FE）建模和分析进行研究，有限元建模和分析是一种基于物理的数值技术，被工程师广泛用于评估物理系统的机械行为。有限元分析（FEA）提供了一个真正新颖的角度对形式功能的关系，但还没有访问到大多数生物学家。一个目标是通过实现两个特定的方法目标，使有限元分析更容易：1）确定哺乳动物头骨的FE模型可以简化的程度，仍然产生足够准确的结果，2）开发协议，有效地转换CT扫描到三维FE模型。这些结果将通过同行评审的科学出版物，演讲和研讨会传达给生物界。功能解剖学家和机械工程师之间的这种合作提供了一个很好的机会，培养研究生，并使本科生接触到生物力学，比较解剖学和机械工程的合作，跨学科研究。研究生研究助理将进行自己的原创研究，并帮助PI指导4 - 6个本科生研究项目。这些项目将作为生物学和/或工程学研究生学习的跳板。

Biting Style and the Biomechanics of Feeding in MammalsElizabeth R. Dumont (PI), Ian R. Grosse (Co-PI)University of Massachusetts, AmherstThe evolutionary history of mammals is largely a story about exploiting an ever broader array of food resources. While the first mammals were insect-eaters, modern mammals specialize in diets ranging from insects to fruits, foliage, meat, and plankton. This diversity in diet is reflected in the shape of the skull - the primary 'tool' that mammals use to bite and chew food. Importantly, however, the underlying mechanism driving the evolution of this diversity is unknown. This study explores the importance of the biomechanical link between the forces generated during biting and the anatomy of mammal skulls that safely and optimally bear and disperse these forces. Further, this study investigates the role of this relationship in the evolution of diversity in skull shape.Previous analyses of mammalian feeding have taken one of two approaches, each of which has inherent limitations. Broad comparative studies document correlations between skull shape and diet, but fall short of testing the causal mechanisms underlying the correlations. On the other hand, detailed experimental studies document how bones and muscles behave during feeding, but the experimental conditions are often far from natural. This study will be the first to combine data on biting behavior and bite force gathered in the field with biomechanical experiments carried out in the laboratory.The first aim is to investigate how different biting styles apply loads to the skull and how those loads are dispersed. Causal links between routine biting behaviors and morphology will be identified by comparing the loading regimes imposed by different biting styles within species. The second aim is to address two other unresolved issues regarding feeding in mammals: the extent to which skull shape is limited by other sensory systems (in this case, vision), and the strength of the facial skeleton relative to forces generated during feeding. Answers to these issues may explain why some lineages of mammals exhibit a wider variety of skull shapes than do others. Initially, the forces generated by biting will be measured and the feeding behavior of mammals will be documented in the field. Next, the mechanical implications of these behaviors will be investigated in the laboratory using finite element (FE) modeling and analysis, a physics-based numerical technique widely used by engineers to assess the mechanical behavior of physical systems. FE analysis (FEA) provides a truly novel perspective on form-function relationships, but is not yet accessible to most biologists. An objective is to make FEA more accessible by accomplishing two specific methodological aims: 1) determine the extent to which FE models of mammal skulls can be simplified and still yield sufficiently accurate results, and 2) develop protocols for efficiently translating CT-scans into three dimensional FE models. These results will be communicated to the biology community through peer-reviewed scientific publications, presentations, and workshops. This collaboration between a functional anatomist and a mechanical engineer offers an excellent opportunity to train graduate students and to expose undergraduates to collaborative, interdisciplinary research in biomechanics, comparative anatomy, and mechanical engineering. Graduate Research Assistants will conduct their own original research, and help the PIs to mentor 4-6 undergraduate research projects. These projects will serve as a springboard to graduate studies in biology and/or engineering.