Gebber Gerard L, Orer Hakan S, Barman Susan M
Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824-1317, USA.
J Neurophysiol. 2006 Feb;95(2):1176-84. doi: 10.1152/jn.01021.2005. Epub 2005 Nov 23.
We used Allan factor analysis to classify time series of the discharges of single presympathetic neurons in the cat medullary lateral tegmental field (LTF) and rostral ventrolateral medulla (RVLM) and of the postganglionic vertebral sympathetic nerve. These time series fell into two classes of fractal-based point processes characterized by statistically self-similar behavior reflecting long-range correlations among data points. Classification of a time series as either a fractional Gaussian noise (fGn)-or fractional Brownian motion (fBm)-based point process depended on the scaling exponent, alpha, of the power law in the Allan factor curve. fGn is defined as 0 < alpha < 1 and fBm as 1 < alpha < 3. The process responsible for the fractal spike trains of 11 of 12 classifiable LTF neurons with sympathetic nerve-related activity was fGn. In contrast, the process responsible for the fractal spike trains of eight of nine classifiable RVLM presympathetic neurons was fBm. The time series of simultaneously recorded vertebral sympathetic nerve discharge and the arterial pulse also were fBm-based signals. Because a fBm signal is the cumulative sum of the elements comprising the corresponding fGn signal, these results show smoothing of fractal time series in a feedforward direction from medullary presympathetic neurons to postganglionic sympathetic neurons. This may involve integration by RVLM neurons of their LTF inputs or independent fractal processes acting at different levels of the network controlling sympathetic nerve discharge. Whether feedforward smoothing of fractal signals is a feature in other neural systems is open to investigation.
我们使用阿伦因子分析对猫延髓外侧被盖区（LTF）、延髓头端腹外侧区（RVLM）单个节前交感神经元以及节后椎旁交感神经放电的时间序列进行分类。这些时间序列分为两类基于分形的点过程，其特征是具有反映数据点之间长程相关性的统计自相似行为。将时间序列分类为基于分数高斯噪声（fGn）或分数布朗运动（fBm）的点过程取决于阿伦因子曲线中幂律的标度指数α。fGn定义为0 < α < 1，fBm定义为1 < α < 3。12个可分类的具有交感神经相关活动的LTF神经元中，有11个的分形峰电位序列的产生过程为fGn。相比之下，9个可分类的RVLM节前交感神经元中，有8个的分形峰电位序列的产生过程为fBm。同时记录的椎旁交感神经放电和动脉脉搏的时间序列也是基于fBm的信号。由于fBm信号是构成相应fGn信号的元素的累积和，这些结果表明分形时间序列在从前庭节前交感神经元到节后交感神经元的前馈方向上得到了平滑。这可能涉及RVLM神经元对其LTF输入的整合，或者是在控制交感神经放电的网络不同层次上起作用的独立分形过程。分形信号的前馈平滑是否是其他神经系统的一个特征尚有待研究。
