Mäkinen S, Hartikainen K, Eriksson J T, Jäntti V
Laboratory of Electricity and Magnetism, Tampere University of Technology, Finland.
Int J Neural Syst. 1996 Sep;7(4):481-7. doi: 10.1142/s0129065796000464.
In this paper we have studied cortical dynamics as assessed using graphical methods during deep anaesthesia. Graphical analysis was carried out by autocorrelation functions and return maps with different lags. During moderate and deep anaesthesia, the electroencephalogram (EEG) shows a burst suppression pattern, consisting of abruptly-occurring high amplitude bursts alternating with periods of relative silence. Deep anaesthesia with burst suppression pattern provides a simple model of brain activity when the noise that is usually present in a subject who is awake is suppressed. During anaesthesia-induced EEG suppression, the brain reacts to different external stimuli with bursts. In respect to sensory processing during anaesthesia, it is interesting to know whether these bursts have different dynamics depending on the stimuli used. We have used graphical analysis to reveal the possible differences in bursts evoked by different stimuli. Externally evoked bursts were induced by auditory, electric and visual stimuli. The EEG studied in this paper consists of 25 bursts from one subject. We have estimated the autocorrelation function for each burst and used the formation gained from such autocorrelation coefficients as the grounds for determining different lags for return maps. The graphical methods used revealed differences in dynamics and topology of bursts as evoked by different stimuli. Spontaneous bursts clearly had different dynamics from evoked burst; which could not be seen directly from the raw EEG data. This study suggests that graphical analysis is a useful tool to obtain information about the dynamics of neuronal processes behind cortical responses during deep anaesthesia.
在本文中，我们研究了在深度麻醉期间使用图形方法评估的皮质动力学。通过自相关函数和具有不同滞后的返回映射进行图形分析。在中度和深度麻醉期间，脑电图（EEG）显示出爆发抑制模式，由突然出现的高振幅爆发与相对安静的时期交替组成。具有爆发抑制模式的深度麻醉提供了一个简单的大脑活动模型，此时清醒受试者中通常存在的噪声被抑制。在麻醉诱导的脑电图抑制期间，大脑会以爆发的形式对不同的外部刺激做出反应。关于麻醉期间的感觉处理，了解这些爆发是否根据所使用的刺激而具有不同的动力学是很有趣的。我们使用图形分析来揭示不同刺激诱发的爆发中可能存在的差异。外部诱发的爆发由听觉、电和视觉刺激引起。本文研究的脑电图由一名受试者的25次爆发组成。我们估计了每次爆发的自相关函数，并将从这些自相关系数中获得的信息作为确定返回映射不同滞后的依据。所使用的图形方法揭示了不同刺激诱发的爆发在动力学和拓扑结构上的差异。自发爆发的动力学明显不同于诱发爆发；这从原始脑电图数据中无法直接看出。这项研究表明，图形分析是获取深度麻醉期间皮质反应背后神经元过程动力学信息的有用工具。
