Modifications of EEG Related to Repeated Static Grasp Efforts Developed by the Hand in Humans

The characteristics of EEG recorded before, in the course, and after three sequential static grasp efforts developed by the right hand were analyzed in 14 healthy volunteers of both sexes, 19 to 56 years old. The grasps were 3 min long, and intervals between the sequential trials were 5 min long. The mean intensity was, as a rule, the greatest in the first trial and decreased, because of fatigue, in the second and third trials. In the course of the grasp effort, significant (P ≤ 0.05) or close to significant decreases in the spectral power were observed in all trials within the alpha2 subrange in some frontal, central, and central/temporal leads. This reaction of desynchronization of alpha2 oscillations probably reflects activation of the sensorimotor cortical zones. Within the above period, the power of alpha2 oscillations increased in the occipital leads. In a few leads of the frontal group, the powers of delta, theta1, theta2, and alpha1 oscillations increased significantly (P < 0.05) in the course of the first trial. Such reaction was not observed in the second and third trials, while the powers of delta and alpha1 ranges increased in the occipital sites (P < 0.05). The powers of delta and theta oscillations increased, as compared with the control values, after the second and third grasps. Such specific EEG modifications in sequential trials can be related to the actions of a novelty factor in the first trial and a fatigue factor in the subsequent trials. The coherence coefficient (CC) of alpha and beta oscillations for symmetric leads usually increased in the course of the grasp. This effect reached a significance level (P < 0.05) for alpha2 oscillations in central, posterotemporal, parietal, and occipital pairs. The CC for beta2 oscillations increased in both temporal lead pairs. A drop in the interhemisphere coherence was more typical of the delta and theta1 ranges. Therefore, changes in the CC values show that the structure of interhemisphere interaction undergoes modifications with the development of the grasp static efforts. Neirofiziologiya/Neurophysiology, Vol. 37, No. 4, pp. 362–371, July–August, 2005.     

Effect of cold stimulation of the arm fingers on the spectral/coherent EEG characteristics in humans

Examination of modifications of EEG in humans induced by cold stimulation of the arm fingers showed that the EEG frequency composition noticeably depended on this thermal influence (in the relaxed state with no movements or during realization of voluntary cyclic movements by the fingers of another arm). In the resting state, cold stimulation mostly induced intensification of the delta activity, while, when coinciding with the performance of voluntary movements, it also resulted in increases in the powers of oscillations of the alpha1 and beta1 ranges. The structure of changes in the coefficients of coherence under the influence of cooling also depended on the conditions of testing (in the resting state or during motor activity). Therefore, the effect of tonic cold stimulation on the interaction between synchronizing and desynchronizing cerebral systems and interrelations between different cortical zones was modified under conditions of realization of a motor function. Neirofiziologiya/Neurophysiology, Vol. 40, No. 3, pp. 268–270, May–June, 2008.     

功率谱熵在痫性发作大鼠脑电检测中的应用研究

目的:研究功率谱熵在痫性发作大鼠脑电检测中的应用。方法:采用青霉素在大鼠海马微注射制备急性痫性发作模型,以深部电极记录大鼠原始脑电信号,将24只SD大鼠随机分成四组,即正常组(A),对照组(B),单电极组(C),多电极组(D)。C、D组大鼠经致痫后观察未发作期、发作前期、发作期和发作后期四期脑电信号的变化,运用谱熵对四期脑电信号进行分析,并与A、B组进行对比。结果:C组和D组脑电功率谱熵显示两组发作期与未发作期、发作前期、发作后期比较有显著差异(P0.05),发作期明显低于其它各期;未发作期和发作前期相比有明显差异(P0.05),发作前期较未发作期降低;将D组大鼠海马致痫灶(a)及其同侧附近(b)、对侧(c)三点发作各期脑电功率谱熵进行对比分析,发作前期和发作期a、b、c三点比较有明显差异(P0.05),a点最低,c点的功率谱熵值最高。结论:功率谱熵可以预报痫性发作并可对癫痫病灶的定位提供一定的帮助。     

Statistical Comparison of Band Spectral Power: An Aid in Stochastical Analysis of Brain Electrical Activity Part 1: Approximation of the distribution of broad band power by a χ2-distribution

In this study the distribution of estimated broad band spectral power is evaluated. Under weak assumptions it is possible to appropriate this distribution by a χ2-distribution and to construct tolerance intervals with great statistical accuracy. The theoretical results implicate a new methodical basis for statistical comparison of spectral parameters in EEG analysis.