Meng Xiangying, Winkowski Daniel E, Kao Joseph P Y, Kanold Patrick O
Department of Biology, University of Maryland, College Park, Maryland 20742, and.
Center for Biomedical Engineering and Technology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201.
J Neurosci. 2017 Oct 18;37(42):10200-10214. doi: 10.1523/JNEUROSCI.1361-17.2017. Epub 2017 Sep 20.
The cerebral cortex is subdivided into six layers based on morphological features. The supragranular layers 2/3 (L2/3) contain morphologically and genetically diverse populations of neurons, suggesting the existence of discrete classes of cells. In primates and carnivores L2/3 can be subdivided morphologically, but cytoarchitectonic divisions are less clear in rodents. Nevertheless, discrete classes of cells could exist based on their computational requirement, which might be linked to their associated functional microcircuits. Through slice recordings coupled with laser-scanning photostimulation we investigated whether L2/3 of male mouse auditory cortex contains discrete subpopulations of cells with specific functional microcircuits. We use hierarchical clustering on the laminar connection patterns to reveal the existence of multiple distinct classes of L2/3 neurons. The classes of L2/3 neurons are distinguished by the pattern of their laminar and columnar inputs from within A1 and their location within L2/3. Cells in superficial L2 show more extensive columnar integration than deeper L3 cells. Moreover, L3 cells receive more translaminar input from L4. imaging in awake mice revealed that L2 cells had higher bandwidth than L3 cells, consistent with the laminar differences in columnar integration. These results suggest that similar to higher mammals, rodent L2/3 is not a homogenous layer but contains several parallel microcircuits. Layer 2/3 of auditory cortex is functionally diverse. We investigated whether L2/3 cells form classes based on their functional connectivity. We used whole-cell patch-clamp recordings with laser-scanning photostimulation and performed unsupervised clustering on the resulting excitatory and inhibitory connection patterns. Cells within each class were located in different sublaminae. Superficial cells showed wider integration along the tonotopic axis and the amount of L4 input varied with sublaminar location. To identify whether sensory responses varied with sublaminar location, we performed Ca imaging and found that L2 cells were less frequency-selective than L3 cells. Our results show that the diversity of receptive fields in L2/3 is likely due to diversity in the underlying functional circuits.
大脑皮层根据形态学特征可细分为六层。颗粒上层2/3（L2/3）包含形态和基因多样的神经元群体，这表明存在不同类别的细胞。在灵长类动物和食肉动物中，L2/3在形态上可进一步细分，但在啮齿动物中细胞结构划分不太明确。然而，基于其计算需求，可能存在不同类别的细胞，这可能与其相关的功能微电路有关。通过结合激光扫描光刺激的切片记录，我们研究了雄性小鼠听觉皮层的L2/3是否包含具有特定功能微电路的离散细胞亚群。我们对层状连接模式进行分层聚类，以揭示多个不同类别的L2/3神经元的存在。L2/3神经元的类别通过它们从A1内部的层状和柱状输入模式以及它们在L2/3内的位置来区分。浅层L2中的细胞比深层L3中的细胞表现出更广泛的柱状整合。此外，L3细胞从L4接收更多的跨层输入。清醒小鼠的成像显示，L2细胞的带宽高于L3细胞，这与柱状整合中的层状差异一致。这些结果表明，与高等哺乳动物类似，啮齿动物的L2/3不是一个均匀的层，而是包含几个并行的微电路。听觉皮层的第2/3层功能多样。我们研究了L2/3细胞是否根据其功能连接形成类别。我们使用全细胞膜片钳记录结合激光扫描光刺激，并对由此产生的兴奋性和抑制性连接模式进行无监督聚类。每个类别中的细胞位于不同的亚层。浅层细胞在音调轴上显示出更广泛的整合，并且L4输入的量随亚层位置而变化。为了确定感觉反应是否随亚层位置而变化，我们进行了钙成像，发现L2细胞的频率选择性低于L3细胞。我们的结果表明，L2/3中感受野的多样性可能是由于潜在功能电路的多样性。
