GABAergic Interneurons can be subdivided into three subclasses: parvalbumin positive (PV), somatostatin positive (SOM) and serotonin positive neurons. With principal cells (PCs) they form complex networks. We examine PCs and PV responses in mouse anterior lateral motor cortex (ALM) and barrel cortex (S1) upon PV photostimulation in vivo. In ALM layer 5 and S1, the PV response is paradoxical: photoexcitation reduces their activity. This is not the case in ALM layer 2/3. We combine analytical calculations and numerical simulations to investigate how these results constrain the architecture. Two-population models cannot explain the results. Four-population networks with V1-like architecture account for the data in ALM layer 2/3 and layer 5. Our data in S1 can be explained if SOM neurons receive inputs only from PCs and PV neurons. In both four-population models, the paradoxical effect implies not too strong recurrent excitation. It is not evidence for stabilization by inhibition.

中文翻译：

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小鼠皮质网络对光遗传学操纵的响应的潜在机制

GABA能性神经元可分为三个亚类：小白蛋白阳性（PV），生长抑素阳性（SOM）和血清素阳性神经元。通过主单元（PC），它们形成了复杂的网络。我们检查体内PV光刺激后，小鼠前外侧运动皮层（ALM）和桶状皮层（S1）中的PC和PV反应。在ALM层5和S1中，PV响应是矛盾的：光激发会降低其活性。在ALM第2/3层中不是这种情况。我们结合分析计算和数值模拟来研究这些结果如何约束体系结构。两人口模型无法解释结果。具有V1类架构的四人口网络解释了ALM第2/3层和第5层中的数据。如果SOM神经元仅从PC和PV神经元接收输入，则可以解释S1中的数据。在这四个人口模型中，矛盾的效应暗示着不太强烈的循环激励。尚无通过抑制作用稳定的证据。