The role of inhibition in the mapping and plasticity of representations in V1

兴奋和抑制之间的平衡对皮层回路功能至关重要，因此对大脑中表征的形成至关重要。此外，在从癫痫到自闭症和精神分裂症的神经系统疾病中也发现了不平衡。皮质抑制性中间神经元是许多不同细胞类型的不同类别，其在突触后神经元的解剖靶向、其形态和其分子特征方面不同。初级视皮层（V1）是研究皮层回路如何处理信息的一个很好的模型系统，因为简单的视觉刺激可以用来描述每个细胞的选择性反应特性。方向调整是V1细胞的一个重要特性，但我们仍然不知道这种选择性是如何产生的。有一种理论认为，皮质内连接是由具有相似特性和抑制性相互作用的细胞之间反复出现的兴奋性连接提供的，它抑制了对所有方向的反应，对改善这种选择性至关重要。 我计划研究两种类型的抑制，体细胞靶向和树突靶向，是如何参与形成和维持的视觉表征在小鼠的初级视觉皮层。我将使用新的遗传方法来特异性标记抑制性细胞的三种亚型，即体细胞靶向小清蛋白阳性（PV+）、树突靶向钙蛋白阳性（CR+）和树突靶向生长抑素阳性细胞（SOM+）。我预计这两种类型的抑制将表现出独特的取向特性，靶向PV+细胞的胞体将具有尖锐的调谐，这将使它们能够提供高度特异性的前馈抑制，靶向CR+和SOM+细胞的树突将具有宽或平的调谐，使它们能够增强取向调谐的对比度独立性。在这个项目的最后阶段，我将探索这些特定细胞亚型的可塑性，假设PV+细胞将比其他两种细胞类型表现出更高水平的短期可塑性。

The balance between excitation and inhibition is critical to cortical circuit function, and thus to the formation of representations in the brain. Furthermore, imbalances have been discovered in neurological disorders ranging from epilepsy to autism and schizophrenia. Cortical inhibitory interneurons are a diverse class of many distinct cell types, which differ in their anatomical targeting of the post-synaptic neuron, in their morphologies, and in their molecular signatures. The primary visual cortex (V1) is an excellent model system for studying how cortical circuits process information, because simple visual stimuli can be used to describe the selective response properties of each cell. Orientation tuning is an important property of cells in V1, but we still do not know how this selectivity arises. One theory is that intracortical connections, provided by recurrent excitatory connections between cells with similar properties and inhibitory interactions, which suppress responses to all orientations, are critical for refining this selectivity. I plan to study how two types of inhibition, soma-targeting and dendritic targeting, are involved in the formation and maintenance of visual representations in the primary visual cortex of the mouse. I will use newly available genetic approaches to specifically label three subtypes of inhibitory cells, soma-targeting parvalbumin-positive (PV+), dendrite-targeting calretinin-positive (CR+), and dendrite-targeting somatostatin- positive cells (SOM+). I expect that these two types of inhibition will demonstrate unique orientation properties, that soma-targeting PV+ cells will have sharp tuning, which would allow them to provide highly specified feedforward inhibition, and that the dendrite targeting CR+ and SOM+ cells will have broad or flat tuning, allowing them to enhance the contrast-independence of orientation tuning. In the final phase of this project, I will explore the plasticity of these specific subtypes of cells, with the hypothesis that PV+ cells will demonstrate higher levels of short-term plasticity than the other two cells types.