CRCNS: Organization of the locomotor CPG in the rodent spinal cord

描述（由申请人提供）：本项目结合电生理学和建模方法来研究哺乳动物脊髓中协调驱动运动的节律性神经活动的中央模式发生器（CPG）神经回路的组织和神经元组成。本研究将采取一种通用的方法，利用各种自发和诱发的运动模式的扰动（包括运动神经元活动的删除，脊髓病变和药理学操作）作为探针，以了解CPG的组织和功能。分析这些扰动对节律性运动模式和已识别的脊髓活动的影响， interneurons将提供重要的见解脊髓CPG的组织和运作。这些数据将被用来开发一个全面的计算模型的脊髓运动CPG，并完善和验证该模型，使其能够再现正常的运动活动和实验扰动的后果。反过来，该模型将作为一个计算框架来制定预测，以指导随后的实验研究。该项目汇集了两名资深科学家，他们在实验（康奈尔大学的Harris-Warrick博士）和计算（德雷克塞尔大学的Rybak博士）神经科学方面具有互补和重叠的专业知识。它有三个相互关联的目标：1）探索运动神经元的行为和突触驱动的改变， 在屈肌和/或伸肌节律性运动活动中的自发和诱发缺失过程中遗传定义的中间神经元，以定义这些中间神经元在运动CPG中的可能功能。2)探索脊髓降低CPG复杂性的后果 脊髓节段的半切和移除，并比较在缺失期间和突触抑制的药理学阻断后，减少的脊髓中鉴定的中间神经元的行为。3)开发一个全面的计算模型的神经回路形成的运动CPG在新生小鼠脊髓，包括遗传识别的interneurons，并建议他们的角色在运动模式的生成。在目标1和目标2中提出的实验扰动过程中，将该模型用于模拟再现运动神经元和中间神经元活动的特定变化以及整个运动模式。该模型将通过与实验研究的持续互动而逐步发展，并将作为脊髓组织工作概念的测试平台和后续实验验证的预测来源。 智力优点：这项建议是朝着机械化的方向迈出的重要一步。 了解形成脊髓运动CPG的神经回路的组织， 哺乳动物拟议的实验和建模研究也将提供新的见解神经控制的节奏运动行为的一般原则。更广泛的影响：（1）研究和教育的整合：在康奈尔大学和德雷克塞尔大学，这项工作将包括在 为不同层次的学生开设了几门基础神经科学和神经工程课程， 本科生到研究生和医科学生。本科生和研究生将 参与这两个机构的项目。在康奈尔大学，哈里斯-沃里克博士将邀请 该项目每年向代表性不足的少数民族学生提供资助，并将支持两名女科学家，为她们今后的科学事业提供认真的指导。 (2)加强研究和教育的基础设施：两个具有基本不重叠的技术专长的实验室将合作了解运动的神经回路。这一合作将有助于两个实验室将联合收割机计算和电生理方法结合起来研究神经回路。在Drexel开发的模拟包NSM 3.0和本项目开发的所有模型将在项目参与者之间共享，并通过Drexel专门开发的网站提供给其他研究小组。(3)医学影响：现在很明显，包括人类在内的所有脊椎动物都有驱动和协调自发运动的脊髓CPG。这些CPG在上脊髓损伤后存活，并且原则上能够在损伤后恢复运动，如在啮齿动物和猫中所证明的。更好地了解这些CPG的组织和功能将为未来脊髓损伤后运动功能恢复的临床策略提供重要的见解。

DESCRIPTION (provided by applicant): This project combines electrophysiological and modeling approaches to study the organization and neuronal composition of the Central Pattern Generator (CPG) neural circuits in the mammalian spinal cord that coordinate rhythmic neural activity driving locomotion. This study will take a general approach that utilizes various spontaneous and evoked perturbations in the locomotor pattern (including deletions of motoneuron activity, spinal cord lesions and pharmacological manipulations) as probes to understand CPG organization and function. It is proposed that analysis of the influences of these perturbations on the rhythmic motor pattern and the activity of identified spinal interneurons will provide important insights on the spinal CPG organization and operation. These data will be used to develop a comprehensive computational model of the spinal locomotor CPG, and to refine and validate this model, so that it can reproduce both normal locomotor activity and the consequences of experimental perturbations. In turn, the model will serve as a computational framework to formulate predictions to guide subsequent experimental investigations. The project brings together two senior scientists with complementary and overlapping expertise in experimental (Dr. Harris-Warrick at Cornell University) and computational (Dr. Rybak at Drexel University) neuroscience. It has three interlocking objectives: 1) Explore alterations in behavior of, and synaptic drive to, motoneurons and genetically defined interneurons during spontaneous and evoked deletions in flexor and/or extensor rhythmic motor activity, to define the possible function of these interneurons in the locomotor CPG. 2) Explore the consequences of reducing CPG complexity by spinal cord hemisection and removal of spinal segments, and compare the behavior of identified interneurons in the reduced cord during deletions and after pharmacological blockade of synaptic inhibition. 3) Develop a comprehensive computational model of the neural circuits forming the locomotor CPG in the neonatal mouse spinal cord that includes genetically identified interneurons and suggests their roles in the generation of the locomotor pattern. Validate this model in simulations reproducing the specific transformations in motoneuron and interneuron activity and the entire locomotor pattern during experimental perturbations proposed in objectives 1 and 2.The model will be progressively developed by continuous interaction with the experimental studies, and will serve both as a testbed for working concepts on spinal cord organization and as a source of predictions for subsequent experimental validation. Intellectual Merit: This proposal represents an important step toward a mechanistic understanding of the organization of the neural circuits forming the spinal locomotor CPG in mammals. The proposed experimental and modeling studies will also provide novel insights into the general principles of neural control of rhythmic motor behaviors. Broader Impacts: (1) Integration of research and education: At Cornell and Drexel, this work will be included in several courses on basic neuroscience and neuroengineering for students at many levels, from undergraduate to graduate and medical students. Undergraduate and graduate students will participate in this project at both institutions. At Cornell, Dr. Harris-Warrick will invite an underrepresented minority student to work on this project each year, and the project will support two female scientists who will be given careful mentoring for a future career in science. (2) Enhance infrastructure for research and education: Two laboratories with mostly nonoverlapping technical expertise will collaborate to understand the neural circuitry for locomotion. This collaboration will help both laboratories to combine computational and electrophysiological approaches to the study of neural circuits. The simulation package NSM 3.0, developed at Drexel, and all models developed in this project will be shared between project participants and made available to other research groups via a specially developed website at Drexel. (3) Medical Impact: It is now clear that all vertebrates, including humans, have spinal CPGs that drive and coordinate locomotor movements. These CPGs survive upper spinal cord injuries, and are in principle capable of restoring locomotion after injury, as demonstrated in rodents and cats. Better understanding of the organization and function of such CPGs will provide essential insights into future clinical strategies for restoration of locomotor function after spinal cord injury.