Differential activity-dependent development of corticospinal control of movement and final limb position during visually guided locomotion
Differential activity-dependent development of corticospinal control of movement and final limb position during visually guided locomotion
复制标题
DOI：
10.1152/jn.00750.2006
复制
发表时间：
2007-05-01
影响因子：
2.5
通讯作者：
Martin, J. H.
中科院分区：
文献类型：
--
作者：
Friel, K. M.;Drew, T.;Martin, J. H.
虽然我们知道，活动和使用依赖性的过程是重要的，在确定皮质脊髓轴突终末的发展在脊髓中，鲜为人知的是，这些过程中的作用，在发展中的肢体运动的熟练控制。在本研究中，我们确定的影响，单侧运动皮层活动阻滞蝇蕈醇输注皮质脊髓轴突终末细化期间，出生后5-7周之间，视觉引导运动。我们研究了步进和前爪放置在水平梯子的梯级和步态的修改，动物在跑步机行走过程中跨过障碍。当猫穿过水平梯时，失活对侧肢体在梯级上比同侧肢体明显更靠前，表明终点控制有缺陷。同样，当动物在跑步机上跨过障碍物时，对侧肢体会被放置在障碍物前面更远的地方，但仅当它是第一个时（即，引导）肢体跨过障碍物，而不是当它是第二个（即，拖曳）肢。这也表明存在终点控制缺陷。相比之下，无论是在梯子上行走，也不是当踏在跑步机上的障碍，有任何一致的证据表明，在肢体轨迹的重大损害。这些结果表明，运动轨迹控制和终点控制的不同和可能独立的皮质脊髓机制。虽然在出生后早期发育过程中，需要皮质脊髓活动来完善回路以实现精确的终点控制，但这种活动依赖性的完善对于运动轨迹控制是不需要的。
Although we understand that activity-and use-dependent processes are important in determining corticospinal axon terminal development in the spinal cord, little is known about the role of these processes in development of skilled control of limb movements. In the present study we determined the effects of unilateral motor cortex activity blockade produced by muscimol infusion during the corticospinal axon terminal refinement period, between postnatal weeks 5-7, on visually guided locomotion. We examined stepping and forepaw placement on the rungs of a horizontal ladder and gait modifications as animals stepped over obstacles during treadmill walking. When cats traversed the horizontal ladder, the limb contralateral to inactivation was placed significantly farther forward on the rungs than the ipsilateral limb, indicating defective endpoint control. Similarly, when animals stepped over obstacles on a treadmill, the contralateral limb was placed farther in front of the obstacle, but only when it was the first (i.e., leading) limb to step over the obstacle, not when it was the second (i.e., trailing) limb. This is also indicative of an endpoint control deficit. In contrast, neither during ladder walking, nor when stepping over obstacles on the treadmill, was there any consistent evidence for a major impairment in limb trajectory. These results point to distinct and possibility independent corticospinal mechanisms for movement trajectory control and endpoint control. Although corticospinal activity during early postnatal development is needed to refine circuits for accurate endpoint control, this activity-dependent refinement is not needed for movement trajectory control.