Department of Medical Neurobiology, Institute of Medical Research Israel-Canada, The Hebrew University - Hadassah Medical School Jerusalem, Israel.
Front Syst Neurosci. 2011 Jun 30;5:54. doi: 10.3389/fnsys.2011.00054. eCollection 2011.
In the healthy primate, neurons of the external and internal segments of the globus pallidus (GP) present a primarily irregular firing pattern, and a negligible level of synchrony is observed between pairs of neurons. This holds even for neighboring cells, despite their higher probability to receive common inputs and to innervate each other via lateral connectivity. In the Parkinsonian primate, this changes drastically, and many pairs of GP cells show synchronous oscillations. To address the relation between distance and synchrony in the Parkinsonian state, we compared the synchrony of discharge of close pairs of neurons, recorded by the same electrode, with remote pairs, recorded by different ones. However, spike trains of neighboring cells recorded by the same extracellular electrode exhibit the shadowing effect; i.e., lack of detection of spikes that occur within a few milliseconds of each other. Here, we demonstrate that the shadowing artifact can both induce apparent correlations between non-correlated neurons, as well as conceal existing correlations between neighboring ones. We therefore introduced artificial shadowing in the remote pairs, similar to the effect we observed in the close ones. After the artificial shadowing, neighboring cells did not show a higher tendency to oscillate synchronously than remote ones. On the contrary, the average percentage (over all sessions) of artificially shadowed remote pairs exhibiting synchronous oscillations was 35.4% compared to 17.2% in the close ones. Similar trend was found when the unshadowed remote pairs were separated according to the estimated distance between electrode tips: 29.9% of pairs at approximate distance of less than 750 μm were significantly synchronized, in comparison with 28.5% of the pairs whose distance was more than 750 μm. We conclude that the synchronous oscillations in the GP of MPTP treated primates are homogenously distributed.
在健康的灵长类动物中，苍白球内外节的神经元呈现出主要的不规则放电模式，并且在神经元对之间观察到几乎没有同步性。即使对于相邻的细胞也是如此，尽管它们更有可能接收共同的输入，并通过横向连接彼此支配。在帕金森病灵长类动物中，这种情况发生了巨大变化，许多对苍白球细胞表现出同步振荡。为了研究帕金森病状态下距离和同步性之间的关系，我们比较了通过同一电极记录的接近神经元对的放电同步性与通过不同电极记录的远程神经元对的放电同步性。然而，通过同一细胞外电极记录的相邻细胞的尖峰序列表现出阴影效应，即缺乏检测彼此之间相隔几毫秒发生的尖峰。在这里，我们证明了阴影伪影既可以诱导非相关神经元之间的明显相关性，也可以掩盖相邻神经元之间的现有相关性。因此，我们在远程神经元对中引入了人工阴影，类似于我们在近距离神经元对中观察到的效果。在引入人工阴影后，相邻的细胞并没有比远程的细胞表现出更高的同步振荡倾向。相反，在所有的实验中，人工阴影的远程神经元对表现出同步振荡的平均百分比（所有实验中）为 35.4%，而近距离神经元对的平均百分比为 17.2%。当根据电极尖端之间的估计距离分离未被阴影遮挡的远程神经元对时，也发现了类似的趋势：在接近距离小于 750μm 的神经元对中，有 29.9%的神经元对表现出显著的同步振荡，而距离大于 750μm 的神经元对中，有 28.5%的神经元对表现出显著的同步振荡。我们得出结论，MPTP 处理的灵长类动物苍白球中的同步振荡是均匀分布的。
