Evaluating the functional organization of forelimb and hindlimb internal copy pathways in the lateral reticular nucleus

评估外侧网状核前肢和后肢内部复制通路的功能组织

• 批准号: 10392883
• 负责人: Kee Wui Huang
• 金额: $ 5.82万
• 依托单位: SALK INSTITUTE FOR BIOLOGICAL STUDIES
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-03-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10392883
• 关键词: 3-Dimensional; Address; Affect; Anatomy; Body part; Brain; Brain Stem; Cell Nucleus; Cells; Cerebellum; Cervical; Complex; Conflict (Psychology); Data; Disease; Electrophysiology (science); Etiology; Fluorescent in Situ Hybridization; Food; Forelimb; Functional disorder; Genes; Genetic; Goals; Helper Viruses; Hindlimb; Human; Impairment; Individual; Injury; Interneurons; Lateral; Life; Limb structure; Locomotion; Lumbar spinal cord structure; Maps; Modeling; Modernization; Molecular; Molecular Genetics; Monitor; Motor; Motor output; Movement; Movement Disorders; Mus; Muscle; Muscle Contraction; Neurons; Neurophysiology - biologic function; Outcome; Output; Pathway interactions; Pattern; Process; Quality of life; Rabies virus; Reporting; Role; Signal Transduction; Spatial Distribution; Speed; Spinal; Spinal Cord; Structure; Testing; Work; experimental study; in vivo; insight; kinematics; limb movement; molecular subtypes; nerve supply; nervous system disorder; neural circuit; optogenetics; rabies label; receptive field; recruit; relating to nervous system; response; segregation; spinal pathway; tomography; tool; treadmill; two-photon; virus genetics

The coordinated execution of movement requires the rapid and continuous refinement of neural activity that drives muscle contraction, a process that is impaired in many forms of injury and disease. In particular, many human movement disorders have been associated with dysfunction of the cerebellum, reinforcing the need for a better understanding of cerebellar circuits. The cerebellum is thought to perform computations necessary for the rapid adjustment of motor output by using internal copies of motor commands to predict movement outcomes. The lateral reticular nucleus (LRN) is a major brainstem nucleus that receives ascending internal copies from the spinal cord and conveys these signals to the cerebellum. Yet little is known about how these motor copy signals are organized and processed in the LRN to facilitate coordinated movement. The LRN is a heterogeneous structure that is classically divided into anatomical subregions. Ascending cervical and lumbar spinal inputs are somatotopically segregated and largely innervate distinct subregions within the LRN, suggesting that LRN neurons are organized into distinct subcircuits that compartmentalize internal copies to regulate the movement of different limbs. Moreover, preliminary findings have revealed at least two molecularly distinct subtypes of LRN neurons that are distributed into different anatomical subregions, potentially forming the cellular basis for these somatotopically organized subcircuits. However, separate studies have shown that a subset of LRN neurons have wide receptive fields spanning multiple limbs, suggesting a convergence of cervical and lumbar inputs onto individual LRN neurons. These findings support a competing model whereby the LRN integrates internal copies from different body parts to coordinate complex multi-limb movements. These two models of divergence versus convergence have contrasting implications for LRN function. The major goal of this proposal is to take advantage of genetic access and molecular tools in mice to resolve these conflicting models. To achieve this goal, Aim 1 will map the connectivity and identity of inputs to each molecularly distinct LRN neuron subtype using viral, genetic, and electrophysiological approaches. These experiments will address the hypothesis that the two discrete LRN neuron subtypes are innervated by distinct sets of inputs that differ in their spatial distributions and molecular identities. Aim 2 will functionally dissect the contributions of these distinct LRN neuron subtypes to forelimb versus hindlimb movements using in vivo electrophysiology and optogenetic perturbations during multi- limb and forelimb-specific movements. These experiments will address the hypothesis that LRN neuron subtypes have different patterns of activity during forelimb versus hindlimb movements, and specific perturbations targeting each LRN neuron subtype will induce distinct movement deficits. This work will provide detailed insights into the functional organization of internal copy cerebellar circuits, and should contribute towards a mechanistic understanding of the etiology of human cerebellar movement disorders.

运动的协调执行需要驱动肌肉收缩的神经活动的快速和持续的改进，这是一个在许多形式的损伤和疾病中受损的过程。特别是，许多人类运动障碍与小脑功能障碍有关，加强了对小脑回路更好理解的需要。小脑被认为通过使用运动命令的内部副本来预测运动结果，从而执行快速调整运动输出所必需的计算。外侧网状核（LRN）是一个主要的脑干核团，它接收来自脊髓的上行内部副本，并将这些信号传递到小脑。然而，关于这些运动复制信号如何在LRN中组织和处理以促进协调运动的知之甚少。LRN是一种异质结构，通常分为解剖学亚区。上升的颈椎和腰椎的脊髓输入是somatotopically隔离，并在很大程度上支配不同的亚区内的LRN，这表明LRN神经元被组织成不同的子电路，划分内部副本，以调节不同的肢体运动。此外，初步研究结果显示，LRN神经元至少有两种分子上不同的亚型，分布在不同的解剖亚区，可能形成这些躯体组织的亚回路的细胞基础。然而，单独的研究表明，LRN神经元的子集具有跨越多个肢体的宽感受野，这表明颈部和腰部输入会聚到单个LRN神经元上。这些发现支持了一个竞争模型，即LRN整合了来自不同身体部位的内部副本，以协调复杂的多肢体运动。这两种发散与收敛的模型对LRN功能有着截然不同的影响。该提案的主要目标是利用小鼠的遗传访问和分子工具来解决这些相互冲突的模型。为了实现这一目标，Aim 1将使用病毒，遗传和电生理方法将输入的连接性和身份映射到每个分子上不同的LRN神经元亚型。这些实验将解决的假设，这两个离散的LRN神经元亚型的支配不同的输入集，不同的空间分布和分子身份。目的2将在多肢和前肢特异性运动期间使用体内电生理学和光遗传学扰动功能性地剖析这些不同的LRN神经元亚型对前肢与后肢运动的贡献。这些实验将解决LRN神经元亚型在前肢与后肢运动期间具有不同的活动模式的假设，并且针对每个LRN神经元亚型的特定扰动将诱导不同的运动缺陷。这项工作将提供详细的内部复制小脑电路的功能组织的见解，并应有助于对人类小脑运动障碍的病因机制的理解。