Rouiller E M, Yu X H, Moret V, Tempini A, Wiesendanger M, Liang F
Institute of Physiology, Faculty of Sciences, University of Fribourg, Switzerland.
Eur J Neurosci. 1998 Feb;10(2):729-40. doi: 10.1046/j.1460-9568.1998.00075.x.
Infant monkeys were subjected to unilateral lesions of the motor cortex (mainly its hand representation). After maturation, they showed normal use of the contralateral hand for global grip movements. However, as compared with the ipsilateral hand, precision grip tasks requiring relatively independent finger movements were performed with less dexterity, particularly if adjustments of the wrist position were necessary. The purpose of this study was to investigate mechanisms which may be responsible for the rather well, although not complete, preservation of manipulative behaviour of these adult monkeys. To this end, the hand representations were mapped bilaterally with intracortical microstimulation in the mature monkeys, and the dexterity of both hands assessed quantitatively in a precision grip task. The behavioural effects of reversible inactivations of the primary (M1) and supplementary (SMA) motor cortical areas were then tested. The following were found. (i) The hand contralateral to the lesion exhibited subtle but significant dexterity deficits, as compared with the ipsilateral hand; the deficit was essentially for complex movements requiring dissociation of the thumb-index finger pinch from the other digits, involving also an arm rotation. (ii) Reversible inactivation of the M1 hand representation in the intact hemisphere dramatically impaired dexterity of the opposite hand without affecting the ipsilateral hand (contralateral to the early lesion). (iii) A relatively complete hand representation was found to occupy a new territory, medial to the old lesion. (iv) The role of this new displaced representation was crucial for the preserved dexterity of the opposite hand, as evidenced by its functional inactivation. In contrast, inactivation of both SMA cortices did not interfere with the manipulative behaviour. It is thus concluded that the preserved functional capacity of manipulations with the hand opposite the early lesion can be essentially attributed to a cortical reorganization around the old lesion. Under the present experimental conditions, contributions from either the SMA or the intact M1 appear not to be crucial.
幼年猴子接受了单侧运动皮层损伤（主要是其手部代表区）。成熟后，它们对侧手在进行整体抓握动作时使用正常。然而，与同侧手相比，需要相对独立手指运动的精确抓握任务执行起来灵活性较差，尤其是在需要调整手腕位置时。本研究的目的是探究这些成年猴子尽管并非完全但相当良好地保留了操作行为的机制。为此，在成熟猴子中通过皮层内微刺激对双侧手部代表区进行映射，并在精确抓握任务中对双手的灵活性进行定量评估。然后测试了初级运动皮层（M1）和辅助运动皮层（SMA）可逆性失活的行为效应。结果如下：（i）与同侧手相比，损伤对侧的手表现出细微但显著的灵活性缺陷；该缺陷主要针对需要将拇指 - 食指捏合与其他手指分离的复杂动作，还涉及手臂旋转。（ii）完整半球中M1手部代表区的可逆性失活显著损害了对侧手的灵活性，而不影响同侧手（早期损伤的对侧）。（iii）发现一个相对完整的手部代表区占据了旧损伤内侧的新区域。（iv）这个新的移位代表区的作用对于对侧手保留的灵活性至关重要，其功能失活证明了这一点。相比之下，双侧SMA皮层的失活并未干扰操作行为。因此得出结论，早期损伤对侧手保留的操作功能能力基本上可归因于围绕旧损伤的皮层重组。在当前实验条件下，SMA或完整的M1的贡献似乎并不关键。
