Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States.
Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, United States.
Elife. 2021 Apr 14;10:e66836. doi: 10.7554/eLife.66836.
Sensory-guided limb control relies on communication across sensorimotor loops. For active touch with the hand, the longest loop is the transcortical continuation of ascending pathways, particularly the lemnisco-cortical and corticocortical pathways carrying tactile signals via the cuneate nucleus, ventral posterior lateral (VPL) thalamus, and primary somatosensory (S1) and motor (M1) cortices to reach corticospinal neurons and influence descending activity. We characterized excitatory connectivity along this pathway in the mouse. In the lemnisco-cortical leg, disynaptic cuneate→VPL→S1 connections excited mainly layer (L) 4 neurons. In the corticocortical leg, S1→M1 connections from L2/3 and L5A neurons mainly excited downstream L2/3 neurons, which excite corticospinal neurons. The findings provide a detailed new wiring diagram for the hand/forelimb-related transcortical circuit, delineating a basic but complex set of cell-type-specific feedforward excitatory connections that selectively and extensively engage diverse intratelencephalic projection neurons, thereby polysynaptically linking subcortical somatosensory input to cortical motor output to spinal cord.
感觉引导的肢体控制依赖于感觉运动回路之间的通讯。对于手部的主动触摸，最长的回路是皮质上的上行通路的延续，特别是传递触觉信号的 lemnisco-cortical 和皮质皮质通路，通过楔束核、腹后外侧核（VPL）和初级体感（S1）和运动（M1）皮质到达皮质脊髓神经元并影响下行活动。我们在小鼠中描述了这条通路的兴奋性连接。在 lemnisco-cortical 肢体中，双突触楔束→VPL→S1 连接主要兴奋 L4 神经元。在皮质皮质肢体中，来自 L2/3 和 L5A 神经元的 S1→M1 连接主要兴奋下游的 L2/3 神经元，这些神经元兴奋皮质脊髓神经元。这些发现为手部/前肢相关的皮质下回路提供了一个详细的新布线图，描绘了一组基本但复杂的细胞类型特异性的前馈兴奋性连接，这些连接选择性和广泛地参与各种内脑投射神经元，从而将皮质下感觉输入与皮质运动输出与脊髓多突触连接。
