Cerf R, Daoudi A, Ould Hénoune M, el Ouasdad E H
Laboratoire d'Ultrasons et de Dynamique des Fluides Complexes, Unité de Recherche Associée au C.N.R.S. no. 851, Université Louis Pasteur, Strasbourg, France.
Biol Cybern. 1997 Oct;77(4):235-45. doi: 10.1007/s004220050384.
Self-organized neuronal dynamics revealed by cortical alpha-rhythms occur as episodes, which are rarely observed without extraction of the alpha-band from the other spectral components. Three episodes of an unusually long duration of 10 s, two with no signal processing after data recording at the clinic, are described and show evidence of low-dimensional alpha-dynamics. The evidence is gained from an analysis of scaled structures appearing in families of slope curves of the correlation integrals and is checked against time reparametrization. The data for the two unprocessed 10-s episodes are used for a test of the methodology, as well as a re-examination of the adequacy of the model of an autonomous dynamic system in steady state and of the concept of an attractor in brain dynamics investigations. Striking evidence for the model's inadequacy is provided by the episode of subject S1. In this example five consecutive overlapping 6-s sections do show evidence for low-dimensional dynamics, whereas the 10-s section containing those sections does not. The episode of subject 1 provides an example of alpha-activity which may involve self-organized dynamics extending down to low frequencies. The system (the neuronal network) showing episodes of attractor-ruled dynamics, under conditions of blurred and smoothly fading out evidence that it stays on an attractor, is designated as being ruled by a 'shadow-attractor'. This concept is compared with that of a 'quasi-attractor' introduced by H. Haken in studies of physiological systems. One possible mechanism for the observed episodes is proposed, based on a time-dependent number of enslaved sub-systems.
皮层α节律揭示的自组织神经元动力学以事件的形式出现，若不将α频段从其他频谱成分中提取出来，这些事件很少被观察到。本文描述了三个持续时间异常长、长达10秒的事件，其中两个事件在临床数据记录后未进行信号处理，这些事件显示出低维α动力学的证据。该证据来自对相关积分斜率曲线族中出现的标度结构的分析，并经过时间重参数化检验。这两个未经处理的10秒事件的数据用于该方法的测试，以及对稳态下自主动力系统模型的充分性和脑动力学研究中吸引子概念的重新审视。受试者S1的事件为该模型的不充分性提供了显著证据。在这个例子中，五个连续重叠的6秒片段确实显示出低维动力学的证据，而包含这些片段的10秒片段却没有。受试者1的事件提供了一个α活动的例子，它可能涉及延伸到低频的自组织动力学。在模糊且逐渐消失的证据表明系统停留在吸引子上的情况下，显示出吸引子主导动力学事件的系统（神经元网络）被指定为由“影子吸引子”主导。这个概念与H.哈肯在生理系统研究中引入的“准吸引子”概念进行了比较。基于随时间变化的受奴役子系统数量，提出了一种观察到的事件的可能机制。
