In Vivo Analysis of Cortical Projection Neurons

描述（由申请人提供）：人类行为的一个基本方面是进行熟练和有目的的动作的能力。这种能力依赖于完整的新皮层，特别是不同类型的投射神经元，它们将神经信息从新皮层传递到涉及行为的下游回路。有两类皮质投射神经元是我们特别感兴趣的——皮质脊髓神经元，投射到脊髓；皮质纹状体神经元，投射到双侧纹状体。虽然我们已经从脑切片实验中了解了皮质脊髓和皮质纹状体神经元的细胞和突触特性，但由于缺乏选择性记录和操纵这些投射神经元活动的简便方法，关于它们在体内与意志运动相关的活动模式的知识一直受到阻碍。在此，基于先前的离体实验，我们提出了一项研究计划，以开发新的方法来解决这一差距。在一个目标中，我们将开发多种互补的方法来记录醒着的运动小鼠的皮质脊髓和皮质纹状体神经元的活动。在一组研究中，我们将使用体内全细胞记录，以高灵敏度和时间分辨率记录运动皮层神经元，并对细胞类型进行事后鉴定。在平行研究中，我们会感染

DESCRIPTION (provided by applicant): An essential aspect of human behavior is the ability to perform skilled and purposive movements. This ability relies on an intact neocortex, and in particular on different classes of projection neurons that convey neural information from the neocortex to downstream circuits involved in behavior. Two classes of cortical projection neurons are of particular interest - corticospinal neurons, projecting to the spinal cord, and corticostriatal neurons, projecting to the striatum bilaterally. While much has been learned from brain slice experiments about the cellular and synaptic properties of corticospinal and corticostriatal neurons, knowledge about their activity patterns in vivo in relation to volitional movements has been impeded due to a lack of easy to use methods for selectively recording from and manipulating the activity of these projection neurons. Here, building on prior ex vivo experiments, we propose a research program to develop new approaches to address this gap. In one aim, we will develop multiple complementary approaches to record the activities of corticospinal and corticostriatal neurons in the awake, moving mouse. In one set of studies we will use in vivo whole-cell recordings to record from motor cortex neurons at high sensitivity and temporal resolution, with post-hoc identification of cell types. In parallel studies we will infect corticospinal and corticostriatal neurons with recombinant rabies viruses carrying genetically encoded calcium indicators (GECIs), and detect activity either at high resolution using two- photon calcium imaging or at a population level using optical fibers. In our second aim, we will develop methods to manipulate the activities of corticospinal and corticostriatal neurons in the awake, moving mice. By either up- or down-regulate projection neuron activity using optogenetic or pharmacogenetic tools, we will be able to begin to address the question of how corticospinal and corticostriatal neurons' activities are causally related to movement parameters. The proposed research program is innovative and significant, we believe, because it will generate multiple new experimental paradigms for probing the in vivo functions of cortical projection neurons, not only in motor areas but across all of neocortex, and because these tools will be readily applicable to mouse models of neurological disease.