Bilateral corticospinal projections arise from each motor cortex in the macaque monkey: A quantitative study
Bilateral corticospinal projections arise from each motor cortex in the macaque monkey: A quantitative study
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DOI：
10.1002/cne.20051
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发表时间：
2004-05-24
影响因子：
2.5
通讯作者：
Tuszynski, MH
中科院分区：
文献类型：
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作者：
Lacroix, S;Havton, LA;Tuszynski, MH
在灵长类动物中，皮质脊髓投射被认为是通过几乎完全来自皮质的对侧投射来影响精细运动功能的。然而，在各种物种中，该系统的单侧病变经常伴随着显著的功能改善，这增加了该通路的双侧投射可能存在或在损伤后出现的可能性。为了研究猕猴（n = 4）皮质脊髓运动神经元的详细解剖和投影，我们将高分辨率顺行示踪剂生物素化葡聚糖胺（BDA）注射到以右下肢（LE）初级运动皮层为中心的126个部位。腰椎L1、L4和L7水平的投影和终止模式被量化，并通过连续切片重建绘制。值得注意的是，皮质脊髓束（CST）轴突在皮质BDA注射的同侧侧CST中平均下降了10.1 +/- 0.6% (+/- SEM)，在对侧CST中投射了87.9 +/- 1.0%的CST轴突。同侧腹侧CST仅包含所有CST轴突的1.0 +/- 0%，而对侧腹侧CST包含所有轴突的0.3 +/- 0.2%。此外，还发现了一个小的背柱CST投影。脊髓灰质bda标记末端的测量显示，11.2 +/- 2.2%的CST轴突终止于皮质注射侧的同侧，其余的终止于对侧。如前所述，大多数CST轴突终止于脊髓V-VIII层，以及IX层的外侧运动神经元组（支配远端肢体肌肉）。值得注意的是，许多CST轴突穿过脊髓中线（平均每40毫米厚切片19.9±4.9轴突）。详细的单轴突重建显示，大多数同侧突出的侧CST轴突终止于同侧灰质。值得注意的是，我们发现许多同侧CST轴突在背外侧束下降的钮扣样肿胀位于Rexed的IX层内，靠近运动神经元体。因此，起源于单一运动皮层的皮质脊髓轴突的双侧投射可能有助于脊髓运动神经元的双侧控制和灵长类动物精细运动控制的高度进化。此外，来自单个运动皮层的双侧CST投射可能代表损伤后可塑性的潜在来源，以及神经再生策略治疗努力的目标。(C) 2004 Wiley-Liss, Inc。
The corticospinal projection is considered to influence fine motor function through nearly exclusively contralateral projections from the cortex in primates. However, unilateral lesions to this system in various species are frequently followed by significant functional improvement, raising the possibility that bilateral projections of this pathway may exist or emerge after injury. To examine the detailed anatomy and projections of the corticospinal motor neurons in rhesus monkeys (n = 4), we injected the high-resolution anterograde tracer biotinylated dextran amine (BDA) into 126 sites centered about the right lower extremity (LE) primary motor cortex. Projection and termination patterns were quantified at lumbar levels L1, L4, and L7 and mapped by using serial-section reconstructions. Notably, a mean of 10.1 +/- 0.6% (+/- SEM) of corticospinal tract (CST) axons descended in the lateral CST ipsilateral to the cortical BDA injection, and 87.9 +/- 1.0% of total CST axons projected in the contralateral lateral CST. The ipsilateral ventral CST contained only 1.0 +/- 0% of all projecting CST axons, whereas the contralateral ventral CST contained 0.3 +/- 0.2% of all axons. In addition, a minor dorsal column CST projection was identified. Measurement of BDA-labeled terminals in the spinal cord gray matter revealed that 11.2 +/- 2.2% of CST axons terminated ipsilateral to the side of cortical injection, and the remainder terminated contralaterally. As previously reported, most CST axons terminated in spinal cord laminae V-VIII, as well as the laterodorsal motoneuronal group of lamina IX (which innervates distal extremity muscles). Notably, many CST axons crossed the spinal cord midline (mean 19.9 +/- 4.9 axons per 40-mum-thick section). Detailed single-axon reconstructions revealed that most ipsilaterally projecting lateral CST axons terminated in ipsilateral gray matter. Notably, we found that the bouton-like swellings of many ipsilateral CST axons descending in the dorsolateral tract were located within Rexed's lamina IX, in close proximity to motoneuronal somata. Thus, bilateral projections of corticospinal axons originating from a single motor cortex could contribute to bilateral control of spinal motor neurons and to the highly evolved degree of fine motor control in primates. Furthermore, bilateral CST projections from a single motor cortex could represent a potential source of plasticity after injury, as well as a target of therapeutic effort in neural regeneration strategies. (C) 2004 Wiley-Liss, Inc.