Jaw-Muscle Biomechanics in Primates

在国家科学基金会的支持下，Christopher Vinyard博士和合作者将确定三种模型灵长类动物在咀嚼和咬合过程中下颌闭合肌肉的功能。 体质人类学家对灵长类动物的进食器官是如何工作的，以及它在过去6500万年中是如何进化的一直保持着浓厚的兴趣。 对现存灵长类动物的研究描述了咀嚼时颌骨肌肉活动和头骨变形的模式，这对我们目前对进食装置如何工作的理解起了决定性作用。 此外，这些实验数据对于灵长类动物和人类进化的适应性和进化解释至关重要。 尽管灵长类动物进食的实验研究取得了进展，但人类学家仍然缺乏灵长类动物咀嚼时下颌闭合肌肉生物力学的关键信息。在以前研究的基础上，该项目旨在描述具有代表性的新世界卷尾猴（Cebus apella），旧世界猕猴（Macaca fascicularis）和非洲galago（Otolemur crassicaudatus）在咀嚼过程中下颌肌肉的生物力学。 具体而言，将通过肌电图（EMG）收集每个物种下颌肌肉活动的时间和相对幅度的数据。 咀嚼过程中这些肌肉的长度变化将使用声测显微技术进行量化。 肌电图和声测显微镜数据的综合分析将证明活动时下颌肌肉是否缩短、延长或收缩而不改变长度。将使用应变仪记录这些肌肉附近颅骨区域的骨变形，以估计肌肉收缩产生的力。 将结合肌肉的长度变化和力产生的数据来估计功（即，力×长度变化）和咀嚼期间下颌闭合肌肉的功率（功/时间）。 最后，这些实验数据表征颌骨肌肉的生物力学将进行比较，颌骨肌肉纤维结构，纤维类型和颌骨形状之间的这些物种。 这项拟议中的研究将产生新的信息，说明来自三个主要灵长类动物群体的代表在进食过程中下颌肌肉如何收缩和工作。 这一新的数据将有助于人类学家了解灵长类动物如何使用下颌肌肉来产生力量并移动下颌。 此外，由于实验数据是必不可少的描述形式功能的关系，这些数据将有广泛的意义，了解下颌肌肉纤维结构，纤维类型和下颌形状与下颌肌肉功能在灵长类动物。 最后，通过比较三个主要灵长类动物群体的代表的结果，这些数据将有助于测试有关灵长类动物咀嚼功能和进化的几个假设。该项目的一个重要的更广泛的影响是通过将教育和研究相结合来培训学生。 本项目将强调通过积极参与促进学生的学习和培训。 由于涉及动物的实验研究技能只能通过互动学徒制来掌握，而这些机会相对较少，因此该项目将为体质人类学提供重要的教育资源。 此外，该项目还将促进美国三所大学之间的合作。 最后，收集到的关于下颌肌肉功能的数据将为关注人类颞下颌关节和肌筋膜疼痛疾病的医学研究提供重要的基础科学信息，从而造福社会。

With National Science Foundation support, Dr. Christopher Vinyard and collaborators will determine how the jaw-closing muscles function during chewing and biting in three model primate species. Physical anthropologists maintain an enthusiastic interest in how the primate feeding apparatus works and how it has evolved over the past 65 million years. Research on living primates describing the patterns of jaw-muscle activity and bone deformation in the skull during chewing has played a decisive role in developing our current understanding of how the feeding apparatus works. Furthermore, these experimental data have been fundamental to adaptive and evolutionary interpretations of primate and human evolution. Despite the advances offered by experimental studies of primate feeding, anthropologists still lack key information on the biomechanics of primate jaw-closing muscles during chewing. Building on previous research, this project aims to describe the biomechanics of the jaw muscles during chewing in a representative New World capuchin monkey (Cebus apella), Old World macaque monkey (Macaca fascicularis) and African galago (Otolemur crassicaudatus). Specifically, data will be collected on the timing and relative magnitude of jaw muscle activity via electromyography (EMG) in each species. Length changes in these muscles during chewing will be quantified using sonomicrometry technology. Combined analysis of EMG and sonomicrometry data will demonstrate whether jaw muscles are shortening, lengthening or contracting without changing length when active. Bone deformation will be recorded in areas of the skull adjacent to these muscles using strain gauges to estimate the force created by a contracting muscle. Data on length changes and force production for a muscle will be combined to estimate the work (i.e., force x length change) and power (work/time) of the jaw-closing muscles during chewing. Finally, these experimental data characterizing jaw-muscle biomechanics will be compared to jaw-muscle fiber architecture, fiber type and jaw form among these species. The proposed research will generate new information on how jaw muscles contract and do work during feeding in representatives from three major primate groups. This novel data will help anthropologists understand how primates use their jaw muscles to create force and move their jaws. Furthermore, because experimental data are essential to describing form-function relationships, this data will have broad implications for understanding how jaw-muscle fiber architecture, fiber type and jaw form relate to jaw-muscle function in primates. Finally, by comparing results from representatives of three major primate groups, these data will facilitate the testing of several hypotheses relating to primate chewing function and evolution. An important broader impact of this project involves training students through integrating education and research. Promotion of student learning and training through active participation will be emphasized in this project. Because experimental research skills involving animals can only be mastered through interactive apprenticeship and these opportunities are relatively rare, this project will provide a significant educational resource for physical anthropology. Additionally, this project will promote collaboration among three U.S. universities. Finally, the data collected on jaw-muscle function will benefit society by providing important basic science information for medical research focusing on human temporomandibular joint and myofascial pain disorders.