Lack of evidence for direct corticospinal contributions to control of the ipsilateral forelimb in monkey.
Lack of evidence for direct corticospinal contributions to control of the ipsilateral forelimb in monkey.
复制标题
DOI：
10.1523/jneurosci.0257-11.2011
复制
发表时间：
2011-08-03
期刊：
影响因子：
--
通讯作者：
Baker SN
中科院分区：
文献类型：
--
作者：
Soteropoulos DS;Edgley SA;Baker SN
强有力的实验证据表明，皮质脊髓束参与对侧前肢的自主控制。其在控制同侧前肢中的潜在作用尚不清楚，尽管已确定了对同侧脊髓回路的解剖投影。我们使用多种方法研究了同侧皮质脊髓束对支配手部和前臂肌肉的运动神经元的输入。三只麻醉猴子的62个运动神经元的细胞内记录显示，在同侧皮质脊髓束刺激后，没有单突触，只有一个弱的寡突触兴奋性突触后电位。对清醒动物的初级运动皮层（M1）进行单刺激的皮质内微刺激未能在同侧肌肉中产生任何反应。强刺激（bbb500 μ a，单次刺激）在髓锥体上的大多数皮质脊髓轴突显示，在较长的潜伏期下，同侧肌肉的抑制较弱，而对侧的促进较强。对M1神经放电（184个细胞）的同侧肌肉活动进行峰触发平均，未发现与单突触皮质神经元连接相一致的任何峰后效应。我们还检查了191个M1神经元在同侧或对侧“到达精确握力”运动中的活动。许多细胞（67%）在同侧肢体运动试验中调节了它们的活动（与对侧试验的90%相比），但这种活动的时间与对侧不运动手臂的弱肌肉活动最相关。我们的结论是，在正常成年人中，任何来自同侧皮质脊髓束的前肢运动神经元的输入都是微弱和间接的，M1细胞放电的调节似乎主要与对侧肢体的控制有关。
Strong experimental evidence implicates the corticospinal tract in voluntary control of the contralateral forelimb. Its potential role in controlling the ipsilateral forelimb is less well understood, although anatomical projections to ipsilateral spinal circuits are identified. We investigated inputs to motoneurons innervating hand and forearm muscles from the ipsilateral corticospinal tract using multiple methods. Intracellular recordings from 62 motoneurons in three anaesthetized monkeys revealed no monosynaptic, and only one weak oligosynaptic excitatory post-synaptic potential following stimulation of the ipsilateral corticospinal tract. Single stimulus intracortical microstimulation of the primary motor cortex (M1) in awake animals failed to produce any responses in ipsilateral muscles. Strong stimulation (>500μA, single stimulus) of the majority of corticospinal axons at the medullary pyramids revealed only weak suppressions in ipsilateral muscles at longer latencies than the robust facilitations seen contralaterally. Spike triggered averaging of ipsilateral muscle activity from M1 neural discharge (184 cells) did not reveal any post-spike effects consistent with monosynaptic corticomotoneuronal connections. We also examined the activity of 191 M1 neurons during ipsilateral or contralateral ‘reach to precision grip’ movements. Many cells (67%) modulated their activity during ipsilateral limb movement trials (compared with 90% with contralateral trials), but timing of this activity was best correlated with weak muscle activity in the contralateral non-moving arm. We conclude that, in normal adults, any inputs to forelimb motoneurons from the ipsilateral corticospinal tract are weak and indirect, and that modulation of M1 cell firing seems to be related primarily to control of the contralateral limb.