Thalamocortical pathways from the rodent ventral posterior (VP) thalamic complex to the somatosensory cerebral cortex areas are a key model in modern neuroscience. However, beyond the intensively studied projection from medial VP (VPM) to the primary somatosensory area (S1), the wiring of these pathways remains poorly characterized. We combined micropopulation tract-tracing and single-cell transfection experiments to map the pathways arising from different portions of the VP complex in male mice. We found that pathways originating from different VP regions show differences in area/lamina arborization pattern and axonal varicosity size. Neurons from the rostral VPM subnucleus innervate trigeminal S1 in point-to-point fashion. In contrast, a caudal VPM subnucleus innervates heavily and topographically second somatosensory area (S2), but not S1. Neurons in a third, intermediate VPM subnucleus innervate through branched axons both S1 and S2, with markedly different laminar patterns in each area. A small anterodorsal subnucleus selectively innervates dysgranular S1. The parvicellular VPM subnucleus selectively targets the insular cortex and adjacent portions of S1 and S2. Neurons in the rostral part of the lateral VP nucleus (VPL) innervate spinal S1, while caudal VPL neurons simultaneously target S1 and S2. Rostral and caudal VP nuclei show complementary patterns of calcium-binding protein expression. In addition to the cortex, neurons in caudal VP subnuclei target the sensorimotor striatum. Our finding of a massive projection from VP to S2 separate from the VP projections to S1 adds critical anatomical evidence to the notion that different somatosensory submodalities are processed in parallel in S1 and S2.

从啮齿动物腹侧后 （VP） 丘脑复合体到体感大脑皮层区域的丘脑皮质通路是现代神经科学的关键模型。然而，除了从内侧 VP （VPM） 到初级躯体感觉区 （S1） 的深入研究投射之外，这些通路的布线仍然很差。我们结合了微群体区域示踪和单细胞转染实验，以绘制雄性小鼠 VP 复合物不同部分产生的通路。我们发现源自不同 VP 区域的通路在面积/层状树枝化模式和轴突静脉曲张大小方面表现出差异。来自喙部 VPM 亚核的神经元以点对点方式支配三叉神经 S1。相比之下，尾部 VPM 亚核主要支配地形第二体感区 （S2），但不支配 S1。第三个中间 VPM 亚核中的神经元通过 S1 和 S2 的分支轴突支配，每个区域的层状模式明显不同。一个小的前背侧亚核选择性地支配颗粒异常的 S1。小细胞 VPM 亚核选择性地靶向岛叶皮层以及 S1 和 S2 的相邻部分。外侧 VP 核 （VPL） 喙部的神经元支配脊髓 S1，而尾部 VPL 神经元同时靶向 S1 和 S2。喙部和尾部 VP 核显示钙结合蛋白表达的互补模式。除了皮层，尾部 VP 亚核中的神经元还以感觉运动纹状体为目标。我们发现从 VP 到 S2 的巨大投影与到 S1 的 VP 投影分开，这为 S1 和 S2 中不同体感子模态并行处理的概念增加了关键的解剖学证据。