Freeman Walter J
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA.
Chaos. 2003 Sep;13(3):1067-77. doi: 10.1063/1.1596553.
My objective of this study was to find evidence of chaotic itinerancy in human brains by means of noninvasive recording of the electroencephalogram (EEG) from the scalp of normal subjects. My premise was that chaotic itinerancy occurs in sequences of cortical states marked by state transitions that appear as temporal discontinuities in neural activity patterns. I based my study on unprecedented advances in spatial and temporal resolution of the phase of oscillations in scalp EEG. The spatial resolution was enhanced by use of a high-density curvilinear array of 64 electrodes, 189 mm in length, with 3 mm spacing. The temporal resolution was advanced to the limit provided by the digitizing step, here 5 ms, by use of the Hilbert transform. The numerical derivative of the analytic phase revealed plateaus in phase that lasted on the order of 0.1 s and repeated at rates in the theta (3-7 Hz) or alpha (7-12 Hz) ranges. The plateaus were bracketed by sudden jumps in phase that usually took place within 1 to 2 digitizing steps. The jumps were commonly synchronized in each cerebral hemisphere over distances of up to 189 mm, irrespective of the orientation of the array. The jumps were usually not synchronized across the midline separating the hemisphere or across the sulcus between the frontal and parietal lobes. I believe that the widespread synchrony of the jumps in analytic phase manifest a metastable cortical state in accord with the theory of self-organized criticality. The jumps appear to be subcritical bifurcations. They reflect the aperiodic evolution of brain states through sequences of attractors that on access support the experience of remembering.
本研究的目的是通过对正常受试者头皮脑电图（EEG）进行无创记录，来寻找人类大脑中混沌游走的证据。我的前提假设是，混沌游走发生在以状态转换为特征的皮质状态序列中，这些状态转换在神经活动模式中表现为时间上的不连续性。我的研究基于头皮EEG振荡相位在空间和时间分辨率方面取得的前所未有的进展。通过使用一个长度为189毫米、间距为3毫米的64电极高密度曲线阵列，空间分辨率得到了提高。通过使用希尔伯特变换，时间分辨率提高到了数字化步长所提供的极限，这里是5毫秒。解析相位的数值导数揭示了持续约0.1秒并以θ（3 - 7赫兹）或α（7 - 12赫兹）范围内的频率重复的相位平台。这些平台被通常在1到2个数字化步长内发生的相位突然跳跃所包围。这些跳跃在每个大脑半球内通常在长达189毫米的距离上同步，与阵列的方向无关。这些跳跃通常不会在分隔半球的中线或额叶与顶叶之间的脑沟两侧同步。我认为解析相位跳跃的广泛同步表明了一种符合自组织临界性理论的亚稳态皮质状态。这些跳跃似乎是亚临界分岔。它们反映了大脑状态通过吸引子序列的非周期性演化，这些吸引子在访问时支持记忆体验。
