Schmidlin Eric, Wannier Thierry, Bloch Jocelyne, Belhaj-Saif Abderraouf, Wyss Alexander F, Rouiller Eric M
Department of Medicine, Faculty of Sciences, University of Fribourg, Chemin du Musée 5, CH-1700 Fribourg, Switzerland.
BMC Neurosci. 2005 Aug 31;6:56. doi: 10.1186/1471-2202-6-56.
After sub-total hemi-section of cervical cord at level C7/C8 in monkeys, the ipsilesional hand exhibited a paralysis for a couple of weeks, followed by incomplete recovery of manual dexterity, reaching a plateau after 40-50 days. Recently, we demonstrated that the level of the plateau was related to the size of the lesion and that progressive plastic changes of the motor map in the contralesional motor cortex, particularly the hand representation, took place following a comparable time course. The goal of the present study was to assess, in three macaque monkeys, whether the hand representation in the ipsilesional primary motor cortex (M1) was also affected by the cervical hemi-section.
Unexpectedly, based on the minor contribution of the ipsilesional hemisphere to the transected corticospinal (CS) tract, a considerable reduction of the hand representation was also observed in the ipsilesional M1. Mapping control experiments ruled out the possibility that changes of motor maps are due to variability of the intracortical microstimulation mapping technique. The extent of the size reduction of the hand area was nearly as large as in the contralesional hemisphere in two of the three monkeys. In the third monkey, it represented a reduction by a factor of half the change observed in the contralesional hemisphere. Although the hand representation was modified in the ipsilesional hemisphere, such changes were not correlated with a contribution of this hemisphere to the incomplete recovery of the manual dexterity for the hand affected by the lesion, as demonstrated by reversible inactivation experiments (in contrast to the contralesional hemisphere). Moreover, despite the size reduction of M1 hand area in the ipsilesional hemisphere, no deficit of manual dexterity for the hand opposite to the cervical hemi-section was detected.
After cervical hemi-section, the ipsilesional motor cortex exhibited substantial reduction of the hand representation, whose extent did not match the small number of axotomized CS neurons. We hypothesized that the paradoxical reduction of hand representation in the ipsilesional hemisphere is secondary to the changes taking place in the contralesional hemisphere, possibly corresponding to postural adjustments and/or re-establishing a balance between the two hemispheres.
在猴子的C7/C8水平进行颈髓半横断后，损伤侧手部会出现数周的瘫痪，随后手部灵活性不完全恢复，在40 - 50天后达到稳定状态。最近，我们证明了稳定状态的水平与损伤大小有关，并且对侧运动皮层中运动图谱的渐进性可塑性变化，尤其是手部代表区，在类似的时间进程中发生。本研究的目的是在三只猕猴中评估损伤侧初级运动皮层（M1）中的手部代表区是否也受到颈髓半横断的影响。
出乎意料的是，基于损伤侧半球对横断的皮质脊髓（CS）束的贡献较小，在损伤侧M1中也观察到了手部代表区的显著减少。映射对照实验排除了运动图谱变化是由于皮质内微刺激映射技术的变异性所致的可能性。在三只猴子中的两只中，手部区域大小减少的程度几乎与对侧半球一样大。在第三只猴子中，它表示减少的幅度是对侧半球观察到变化的一半。尽管损伤侧半球的手部代表区发生了改变，但如可逆性失活实验所示（与对侧半球相反），这种变化与该半球对损伤手部灵活性不完全恢复的贡献无关。此外，尽管损伤侧半球M1手部区域大小减少，但未检测到与颈髓半横断相对侧手部的手部灵活性缺陷。
颈髓半横断后，损伤侧运动皮层的手部代表区显著减少，其程度与轴突切断的CS神经元数量较少不匹配。我们假设损伤侧半球手部代表区的矛盾性减少是对侧半球发生变化的继发结果，则可能对应于姿势调整和/或重新建立两个半球之间的平衡。
