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A critical branching model of activity in local cortical networks.

机译：局部皮质网络中活动的关键分支模型。

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摘要

Recent experimental work has begun to characterize activity in local cortical networks containing hundreds to thousands of neurons. One finding is that neocortical circuits can produce cascades of electrical activity whose sizes follow a power law distribution. Another finding is that these cascades of activity form spatio-temporal patterns that re-occur significantly more often than expected by chance. A simple critical branching model can account for both of these findings from multielectrode recording data. Interestingly, this critical branching model also suggests that local cortical networks are poised to operate near a critical point where information processing would be optimal. In this thesis, we experimentally test three key predictions of the critical branching model.;The first prediction is that local cortical networks operate at a critical point. Although a power law may suggest that these circuits operate near a critical phase transition point, many other non-critical mechanisms can also produce power laws. To explore the origin of this distribution, we recorded cascade sizes and then perturbed activity. Deviations from a power law distribution varied systematically with a control parameter, as expected in a continuous phase transition. We also performed a data collapse analysis, showing that both avalanche size and length distributions exhibited scaling relationships. These results strongly suggest that neocortical circuits belong to the class of critical phenomena.;The second prediction is that changes in the connection weights within the network will alter the trajectories produced by spatio-temporal patterns of activity. Recently there has been an explosion of work on connectivity in networks of all types. It would seem natural then to explore the influence of connectivity on dynamics at the local network level. Dynamics can be measured as a trajectory in state space. We recorded significant changes in connectivity after a pharmaceutical agent was applied. As predicted, agents that changed the network weight structure also altered spatio-temporal trajectories in a manner that was consistent with the critical branching model. Importantly, trajectories at the critical point are dynamically neutral, allowing flexibility without introducing instabilities.;The third prediction is that a skewed distribution of connection weights will optimize the number of significantly repeating spatio-temporal patterns retained in the network. We found that when the model weight distribution was appropriately skewed, it correctly matched the distribution of repeating patterns observed in the data. In addition, the skewed distribution of weights maximized the capacity of the network model to retain stable activity patterns. We conclude that living cortical networks are very likely to use the skewed weight distributions predicted by theory to optimize information retention.;Taken together, these results suggest that the critical branching model can capture important features of the data. In addition, these results support the hypothesis that local cortical networks operate near a critical point where they may optimize information processing.
机译：最近的实验工作已经开始表征包含数百到数千个神经元的局部皮质网络的活动。一个发现是，新皮质电路可以产生级联的电活动，其大小遵循幂律分布。另一个发现是，这些活动级联形成时空模式，其发生频率比偶然预期的要高得多。一个简单的临界分支模型可以解释多电极记录数据中的这两个发现。有趣的是，此关键分支模型还表明，本地皮质网络已准备好在关键点附近运行，在该关键点，信息处理将是最佳的。在本文中，我们对关键分支模型的三个关键预测进行了实验测试。第一个预测是局部皮质网络在关键点运行。尽管功率定律可能暗示这些电路在临界相变点附近工作，但许多其他非关键机制也会产生功率定律。为了探索这种分布的起源，我们记录了级联大小，然后记录了活动。功率定律分布的偏差随控制参数而系统地变化，这在连续相变中是可以预期的。我们还进行了数据崩溃分析，显示雪崩大小和长度分布均显示出比例关系。这些结果强烈表明，新皮层回路属于关键现象类别。第二个预测是，网络内连接权重的变化将改变由时空活动模式产生的轨迹。近来，关于各种类型的网络中的连接性的工作激增。因此，在本地网络级别上探索连接性对动态性的影响似乎很自然。动力学可以作为状态空间中的轨迹来测量。应用药剂后，我们记录了连通性的重大变化。如预期的那样，改变网络权重结构的主体也以与关键分支模型一致的方式改变了时空轨迹。重要的是，关键点处的轨迹是动态中性的，从而允许灵活性而不会引入不稳定性。;第三个预测是，连接权重的偏斜分布将优化网络中保留的明显重复的时空模式的数量。我们发现，当模型权重分布适当偏斜时，它可以正确匹配数据中观察到的重复模式的分布。此外，权重的偏斜分布最大化了网络模型保持稳定活动模式的能力。我们得出结论，活体皮层网络很可能会使用理论上预测的偏权重分布来优化信息保留。总而言之，这些结果表明，关键分支模型可以捕获数据的重要特征。此外，这些结果支持以下假设：本地皮质网络在可能优化信息处理的临界点附近运行。

著录项

  • 作者

    Chen, Wei.;

  • 作者单位

    Indiana University.;

  • 授予单位 Indiana University.;
  • 学科 Physics General.;Biophysics General.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 143 p.
  • 总页数 143
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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