Laboratory of Sensory Processing, Brain Mind Institute, Faculty of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom.
Elife. 2024 Oct 11;13:RP97602. doi: 10.7554/eLife.97602.
Long-range axonal projections of diverse classes of neocortical excitatory neurons likely contribute to brain-wide interactions processing sensory, cognitive and motor signals. Here, we performed light-sheet imaging of fluorescently labeled axons from genetically defined neurons located in posterior primary somatosensory barrel cortex and supplemental somatosensory cortex. We used convolutional networks to segment axon-containing voxels and quantified their distribution within the Allen Mouse Brain Atlas Common Coordinate Framework. Axonal density was analyzed for different classes of glutamatergic neurons using transgenic mouse lines selectively expressing Cre recombinase in layer 2/3 intratelencephalic projection neurons (Rasgrf2-dCre), layer 4 intratelencephalic projection neurons (Scnn1a-Cre), layer 5 intratelencephalic projection neurons (Tlx3-Cre), layer 5 pyramidal tract projection neurons (Sim1-Cre), layer 5 projection neurons (Rbp4-Cre), and layer 6 corticothalamic neurons (Ntsr1-Cre). We found distinct axonal projections from the different neuronal classes to many downstream brain areas, which were largely similar for primary and supplementary somatosensory cortices. Functional connectivity maps obtained from optogenetic activation of sensory cortex and wide-field imaging revealed topographically organized evoked activity in frontal cortex with neurons located more laterally in somatosensory cortex signaling to more anteriorly located regions in motor cortex, consistent with the anatomical projections. The current methodology therefore appears to quantify brain-wide axonal innervation patterns supporting brain-wide signaling.
不同类型的新皮层兴奋性神经元的长程轴突投射可能有助于大脑范围内的感觉、认知和运动信号处理的相互作用。在这里，我们对来自后初级体感皮层和补充体感皮层中遗传定义的神经元的荧光标记轴突进行了光片成像。我们使用卷积网络来分割包含轴突的体素，并在 Allen 小鼠脑图谱共同坐标框架内量化它们的分布。我们使用转基因小鼠系，选择性地在层 2/3 内脑投射神经元（Rasgrf2-dCre）、层 4 内脑投射神经元（Scnn1a-Cre）、层 5 内脑投射神经元（Tlx3-Cre）、层 5 锥体束投射神经元（Sim1-Cre）、层 5 投射神经元（Rbp4-Cre）和层 6 皮质丘脑神经元（Ntsr1-Cre）中表达 Cre 重组酶，分析不同类型谷氨酸能神经元的轴突密度。我们发现来自不同神经元类别的明显的轴突投射到许多下游脑区，这些投射在初级和补充体感皮层之间基本相似。从体感皮层的光遗传学激活和宽场成像获得的功能连接图显示，额皮质中存在具有拓扑组织的诱发活动，位于体感皮层更外侧的神经元信号传递到运动皮质中更靠前的区域，这与解剖学投射一致。因此，当前的方法似乎可以量化全脑范围的轴突支配模式，支持全脑范围的信号传递。
