Longitudinal structure of spinal premotor circuits

项目摘要 当动物移动时，它们不断地协调身体的吻端和尾端之间的活动。这 协调依赖于脊髓中的神经元，这些神经元发出长的向上或向下的轴突投射。 尽管几项研究表明，消融这些神经元会导致协调能力不足，但事实并非如此 这些远程电路与本地电路是相似还是不同，在很大程度上是未知的。在最近 在斑马鱼幼体上发表的数据，我们证明了至少有一种从基因上定义的脊椎 神经元，V1(EN1+)群体，随着其轴突在脊髓中的上升而改变其突触目标。 具体地说，V1神经元与运动神经元和附近的其他腹角神经元形成突触连接， 但在更远的距离上转向抑制背角感觉种群。在这里，我们建议延长这一期限 另外5组腹角神经元dI6、V0兴奋性和抑制性、V2a和V2b的分析 人口。为了创建这个大规模的电路图，我们使用识别出的脊髓的局部光遗传激活 同时对已确定的潜在突触后伙伴进行全细胞记录。通过翻译 在脊髓上下的光遗传刺激下，我们可以构建出生理图谱的强度 不同吻尾位置的突触连接。突触电荷转移的正常化允许 跨目标人群的比较，提供脊髓神经元之间的全面网络连接 在不同的吻尾距离的班级。然后我们将建立一个脊髓连通性的计算模型 这反映了在这些实验中测量到的生物现实。使用此模型，我们将测试 在吻尾轴上移动突触连接的后果，以便理解 脊椎环路组织。最后，我们将有选择地消融远程或局部V2a神经元，以确定 远距离投射与局部投射的行为效应。总之，这些实验将提供一张电路图 基因鉴定的脊髓神经元。

Project Summary As animals locomote, they constantly coordinate activity between the rostral and caudal ends of the body. This coordination relies on neurons in the spinal cord that send long ascending or descending axonal projections. Although several studies have shown that ablation of these neurons leads to deficits in coordination, it is largely unknown whether these long-range circuits are similar or different from local circuits. In recently published data in larval zebrafish, we demonstrated that at least one genetically defined class of spinal neurons, the V1 (En1+) population, changes its synaptic targets as its axon ascends in the spinal cord. Specifically, V1 neurons form synaptic connections with motor neurons and other ventral horn neurons nearby, but switch to inhibiting a dorsal horn sensory population at longer range. Here we propose to extend this analysis to five additional sets of ventral horn neurons, the dI6, V0 excitatory and inhibitory, V2a, and V2b populations. To create this large-scale circuit map, we use localized optogenetic activation of identified spinal populations while carrying out whole-cell recording of identified potential postsynaptic partners. By translating the optogenetic stimuli up and down the spinal cord, we can build a physiological map of the strength of the synaptic connection at various rostrocaudal positions. Normalization of the synaptic charge transfer allows comparisons across target populations, providing a comprehensive grid of connectivity among spinal neuron classes at various rostrocaudal distances. We will then build a computational model of spinal cord connectivity that reflects biological reality, as measured in these experiments. Using this model, we will test the consequences of shifting synaptic connections in the rostrocaudal axis, in order to understand the logic of spinal circuit organization. Finally, we will selectively ablate long-range or local V2a neurons to determine the behavioral effects of long-range vs local projections. Together, these experiments will provide a circuit map of genetically identified spinal neurons.