Precise spatiotemporal repeating patterns in monkey primary and supplementary motor areas occur at chance levels
Precise spatiotemporal repeating patterns in monkey primary and supplementary motor areas occur at chance levels
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DOI：
10.1152/jn.2000.84.4.1770
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发表时间：
2000-10-01
影响因子：
2.5
通讯作者：
Lemon, RN
中科院分区：
文献类型：
--
作者：
Baker, SN;Lemon, RN
神经放电中精确的时空模式是大脑中信息编码的一种可能机制。以前的研究发现，这种模式重复出现，似乎与关键的行为事件有关。这些模式是否发生在偶然水平之上仍然存在争议。为了解决这个问题，我们同时记录了三只猴子的初级运动皮层和辅助运动区的两到九个神经元，同时他们执行精确的抓握任务。在总共67个神经元中，46个被逆向鉴定为锥体束神经元。在60秒长的录音片段中搜索涉及三个或更多个重复至少两次的尖峰的模式。模式重复的允许抖动为3 ms，模式长度被限制为192 ms。在所有11个记录分析，大量的重复模式被发现。为了评估模式的预期机会水平，“替代”数据集被生成。这些具有相同的时刻调制的放电率的实验尖峰列车，并匹配其interspike间隔分布，但没有保留精确的时间个别尖峰。使用10个随机生成的替代品中的重复模式数来形成随机预期的重复模式计数的99%置信限。这些置信限与实验数据中观察到的模式数量之间存在密切的一致性。在四个长记录（平均持续时间23.2分钟，同时记录的神经元的平均数量7.5）进行了高复杂性模式的分析。该分析仅记录了由大量（7-11）尖峰组成的模式。在替代数据集中看到的模式的数量显示出一个小的，但显着超过那些在原始实验数据中看到的;这是在替代生成的上下文中讨论。实验数据中重复模式的发生与精确抓握任务的特定阶段密切相关;然而，对于替代数据，可以看到类似的任务依赖性。当一个重复的模式被用作模板，以找到不精确的匹配，其中多达一半的组件尖峰可能会丢失，相似的匹配数量被发现在实验和替代数据，这种匹配的发生时间显示出相同的任务依赖性。我们的结论是，精确的重复模式的存在，在我们的数据是不是由于皮层机制，有利于这种形式的编码，因为许多，如果不是更多的，模式所产生的尖峰列车构造只调制他们的发射率以相同的方式作为实验数据，并匹配的interspike间隔直方图。模式发生的任务依赖性可以解释为神经放电率调制的伪影。在皮层的时间编码理论的后果进行了讨论。
Precise spatiotemporal patterns in neural discharge are a possible mechanism for information encoding in the brain. Previous studies have found that such patterns repeat and appear to relate to key behavioral events. Whether these patterns occur above chance levels remains controversial. To address this question, we have made simultaneous recordings from between two and nine neurons in the primary motor cortex and supplementary motor area of three monkeys while they performed a precision grip task. Out of a total of 67 neurons, 46 were antidromically identified as pyramidal tract neurons. Sections of recordings 60 s long were searched for patterns involving three or more spikes that repeated at least twice. The allowed jitter for pattern repetition was 3 ms, and the pattern length was limited to 192 ms. In all 11 recordings analyzed, large numbers of repeating patterns were found. To assess the expected chance level of patterns, "surrogate" datasets were generated. These had the same moment-by-moment modulation in firing rate as the experimental spike trains, and matched their interspike interval distribution, but did not preserve the precise timing of individual spikes. The number of repeating patterns in 10 randomly generated surrogates was used to form 99% confidence limits on the repeating pattern count expected by chance. There was close agreement between these confidence limits and the number of patterns seen in the experimental data. Analysis of high complexity patterns was carried out in four long recordings (mean duration 23.2 min, mean number of neurons simultaneously recorded 7.5). This analysis logged only patterns composed of a larger number (7-11) of spikes. The number of patterns seen in the surrogate datasets showed a small but significant excess over those seen in the original experimental data; this is discussed in the context of surrogate generation. The occurrence of repeating patterns in the experimental data were strongly associated with particular phases of the precision grip task; however, a similar task dependence was seen for the surrogate data. When a repeating pattern was used as a template to find inexact matches, in which up to half of the component spikes could be missing, similar numbers of matches were found in experimental and surrogate data, and the time of occurrence of such matches showed the same task dependence. We conclude that the existence of precise repeating patterns in our data are not due to cortical mechanisms that favor this form of coding, since as many, if not more, patterns are produced by spike trains constructed only to modulate their firing rate in the same way as the experimental data, and to match the interspike interval histograms. The task dependence of pattern occurrence is explicable as an artifact of the modulation of neural firing rate. The consequences for theories of temporal coding in the cortex are discussed.