Cross-correlation analysis of the lateral pulvinar and scalp EEG in man

Cross-correlation analysis of the EEG between the lateral pulvinar and various cortical regions was made after EEG was recorded during stereotactic pulvinectomy. Cross-correlation analysis of the alpha-waves between the lateral pulvinar and the scalp EEG showed that the lateral pulvinar has the highest degree of functional connection with the pre-central area, diminishing in degree with the parietal and frontal areas, and has poor functional connections with the occipital area. From these results, it might be concluded that the lateral pulvinar may be related to motor function by functional connections with the pre-central area rather than the parietal area.     

Lateral inhibition in neuronal networks and the shape of alpha-rhythm in the EEG

In 15 volunteers, the background EEG was registered from the right occipital area with eyes closed. Rhythmic photo-stimulation conjugated with a certain phase of the alpha-waves (10 phases) elicited responses that were compared by means of measurement of the alpha-wave average amplitude in each protocol. The wave shape was compared by asymmetry at the level of ascending and descending fronts. The shape changes were most obvious during the stimuli in middle of the descending front, the changes shrply differing from other 9 phases of the stimulation.     

Dynamic values of the EEG factors in the human perception of sound stimuli

In 43 healthy subjects passing from the state of calm alertness to various conditions of perception of short sounds of different height, interchanging at random, the most expressed is a generalized reduction of individual values of the EEG factor I positively related to the index, mean amplitude and regularity of the alpha-activity and also to mean beta- and theta-amplitudes and negatively related to the theta-index. Maximum reaction by this factor is observed at the beginning of the stimulation; at the second minute of the stimulation, the factor values return towards the initial background level, and again, to a lesser degree, are reduced when carrying out tasks on the sound analysis of stimuli, and the more difficult is the task the stronger is the reduction. In all cases the parietal regions are more reactive than the central ones. By the EEG factor II positively related to the index, frequency and regularity of the beta-activity, the reaction is less expressed and is more local: the factor values in the parietal areas augment only at the beginning of stimulation and diminish at the second minute; and in the central parts, on the contrary, there is a tendency to increase only at the second minute of stimulation. At the sound analysis, reaction is poorly expressed by this factor. Changes of values of the EEG-factor III, positively related to the mean period of the alpha-waves and theta-index, are not great and have only a general tendency to increase at the beginning of the stimulation, and to lower to the background level at the second minute.     

On the use of EEG autointervalograms for analyzing the responses to periodic light stimulation

Autointervalograms of the extremums of human electroencephalograms (EEGs) recorded under periodic stimulation were analyzed. The method was compared with visual EEG analysis and EEG sinusoid testing. It was shown that, in most cases, the construction of intervalograms is as good as, or even better than, the other two methods, because it allows us to detect the responses and obtain additional information.     

Correlation between the Activity of Dopaminergic Neurons of the Ventral Tegmentum and Spectral Power of the EEG Rhythms in Awake Cats

We studied correlations between the frequency of background impulse activity (BIA) of dopaminergic (DAergic) neurons of the ventral tegmentum (VT) and spectral power (SP) of the frequency components of EEG samples recorded in awake cats. The EEG was recorded monopolarly (electrodes were fixed in the cranial bones) from the frontal, occipital, and right and left temporal regions of the cortex. In a great majority of the cases, the BIA frequency of VT DA-ergic neurons demonstrated significant positive correlations with changes in the SPs of the alpha and beta EEG rhythms. The closest correlations of the spiking frequency of DA-ergic cells with the SP of the alpha rhythm was observed in the occipital region, while those with the beta SP were found in the frontal area. Correlations of the activity of DA-ergic neurons with the SPs of the alpha and beta rhythms in the left temporal cortical zone were closer, as compared with those in the symmetrical right zone. Correlations of the SPs of the delta, theta, and gamma EEG components with the discharge frequency of VT DA neurons were of opposite directions, and in most cases such correlations did not reach the level of significance. The results of this study show that, in some cases, specific EEG patterns can be considered indicators of the state of the cerebral VT DA-ergic system. Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 359–367, July–August, 2008.     

Influence of artificial air ionisation on the human electroencephalogram

Exposure of 20 subjects to negative ionisation was monitored by EEG. Negative ionisation was supplied by an Ionotron apparatus (Amcor-Amron, Herzlia-Israel) with an output of 3.5 × 10⁵ ions/(cm³ · sec) at 1 m distance. Objective findings in ten normal subjects showed reduction of the frequency of the alpha-waves from 10 or 11 down to 9 or 8 Hz, increase of the amplitude by up to 20%, advance of the alpha rhythm pattern from the occipital to the frontal area and general synchronisation of the EEG records of both hemispheres. These reactions were suppressed in 10 subjects by tranquillisers. Subjective findings included relaxation, alertness, improved working capacity and relief from the Serotonin Irritation Syndrome produced by the positive ionisation of hot, dry desert winds.This paper is devoted to the memory of Dr Igho H.Kornblueh, the pioneer of ion therapy, who passed away in 1973 in Philadelphia. Working on this project in 1957 he concluded "that further research on the effects of ionisation on the EEG is warranted".This report was prepared with the technical assistance of Mrs Suzi Alpern and B.Shalita.     

Evoked potentials to joint presentation of photic and acoustic stimuli in the human EEG

The results are outlined of a comparative estimation of averaged EP recorded in response to simultaneous and separate presentation of photic and acoustic stimuli on EEG of fifteen healthy subjects and twelve patients with focal lesions of the diencephalic structures. Investigation of the EP components and integral-temporal parameters has revealed that in healthy subjects EP to a combined heteromodal stimulation considerably exceeded by amplitude the one recorded in response to a separate presentation of stimuli. In case of lesion of the diencephalic formations, the converging effect of polysensory stimulation for the main waves of the response was less pronounced than in healthy subjects. At the same time, in pathological cases the summation effect of the afteraction potential (recorded after the main EP components as a slow negative oscillation) was manifested most distinctly, especially in the central zone of the cortex.     

Electrical reactions in the cat brain during differentiation of photic stimuli]

Study of EEG responses to photic conditioned stimuli in cats has shown that the extent of brain activation depends not on the physical strength of the stimulus, but on its biological significance. The longest activation is recorded to a positive signal, even if it is the weakest flash of light. The intensity of EEG responses to negative stimuli is determined by the nearness of their physical parameters to those of the positive signal. Repeated presentation of a non-reinforced flash leads to a gradual extinction of EEG reactions. Brain activation in response to a reinforced positive signal persists unchanged even after a large number of its repetitions. The revealed properties of brain electrical reactions to stimuli of different significance accord with those previously recorded in response to acoustic stimuli. In both cases the data are in agreement with hypothesis of a central system of signal analysis, which performs the estimation of stimuli according to their biological quality.     

Phase-shift gradients of dominant cortical potentials in rabbits

Phase shifts of cortical potentials were studied in rabbits before and during photic stimulation and their importance for irradiation of excitation from the visual to the motor area was examined. Both before and during stimulation variations in phase relationships of various kinds were observed. In most cases, however, with an increase in distance between the electrodes, the phase shift of the theta-waves gradually increased. Most motor responses of the rabbits took place in the presence of a marked phase shift gradient. It is suggested that the state of the brain in which a spatial phase shift gradient of the theta-waves is recorded in the EEG is the optimal condition for realization of the motor response. Photic stimulation increases the number of in-phase waves in the EEG recorded from closely situated points and it reduces scatter of the phase shift values between components of the sensomotor and visual cortical EEG, i.e., it leads to an increase in coherence. Motor responses of the rabbits to stimulation take place in the presence of theta-waves with the most constant phase shift in the EEG of the sensomotor and visual cortex.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 512–519, July–August, 1984.     

On Connections of Symmetrical Regions of the Frontal and Occipital Areas of the Human Cortex Based On Eeg Cross-Correlation Data

The problem of the correlation of the electrical activity of various parts of the brain is closely linked with the problem of the functional connections between them. The investigation of such relationships using an index of synchronization of the alpha- or beta-rhythm in a human EEG based on calculations of the coincidence of the phases of oscillations for definite short periods of time has been carried out in a number of studies (Adrian and Yamagiwa [9], Cohn [16], Goodwin and Stein [19], Darrow et al. [17], Garoutte and Aird [18], Adamovich [1]). These investigations revealed a high degree of synchrony at symmetrical points of both hemispheres and a phase lag of alpha-waves in the frontal sections compared to the occipital. In recent years M. N. Livanov et al. [2, 6, 7] have been studying the synchronization of electrical activity of various areas of the cortex of the large hemispheres in man by means of encephaloscopy and subsequent data analysis on electronic computers. They have shown that the degree of synchronization of the EEG of the different sections of the cerebral cortex normally found in man varies significantly and changes under the influence of functional load and pharmacological tests.     

Proton magnetic resonance spectroscopy in diagnostics of epilepsy

Present paper presents proton MRS investigation results. The investigation was carried out with Magnetom Vision device. Twenty-five patients in the age of 20-44 years suffering with generalization epileptic fits validated by EEG (no visible changes on MRT) were examined. In all cases independently on the localization of the changes, decreasing of NAA and increasing of Cho were recorded. At one side temporal lobe injury recorded by EEG at the damaged part decreasing of NAA/Cr and NAA/Cho + Cr ratios were registered. Patients with bilateral changes registered by EEG showed non-equal changes of metabolite concentration on both sides. Examination of patients suffering with distinct symptoms of temple epileptics has shown ipsilaterality decrease of NAA and Cr concentration. But on the injured side NAA/Cr ratio decrease was more distinct. In general, the laterality was recorded in 14 patients out of 22 with pathological changes registered by proton MRS and in 10 patients out of 14 the above mentioned changes corresponds to the side of the fit initiation. In the patients with bilaterality changes NAA/Cr ratio asymmetry was recorded in all cases, but the most distinctly in the medium part of the temple lobe. Comparison of data recorded in 8 patients suffering with one side fit complex has shown significant asymmetry of metabolites which was observed in ipsilaterality and contra laterality NAA ratio obtained in hippocampal areas. Difference in NAA ratio obtained between left and right sides are 19-25%. Left-right ratio of other metabolites corresponded to that ratio in the control group and was symmetrical.     

Effects of EEG of the osmotic opening of the blood-brain barrier in rats

EEG activity was recorded in rats submitted to osmotic opening of the BBB by intracarotid mannitol infusion.This procedure produced an immediate short-lasting depression of the EEG and a tardive paroxysmal EEG activity. Both these phenomena were more relevant on the ipsilateral hemisphere. In some instances a tonico-clonic seizure was recorded.Pre-treatment with diazepam abolished the occurrence of the tardive EEG and behavioral modifications.In accord with previous findings, focal seizure activity is likely to be responsible for the metabolic abnormalities associated with osmotic opening of the BBB. This preparation therefore produces in the brain unphysiological states in respect to local metabolism and electrical function.     

急性轻中度缺氧EEG信号的复杂度研究

建立了一个急性高空缺氧实验模型,记录了四种不同高度条件下从缺氧前(正常呼吸)到缺氧后30分钟时的EEG,分析了其复杂度。发现缺氧引起复杂度明显变化,随时间和高度增加,一定程度缺氧可使EEG复杂度低于正常。表明EEG复杂度对脑缺氧较为敏感,可用于缺氧程度进行评估,有望成为临床诊断的一个指标。     

神经工程与脑-机接口

神经工程是近年来在生物医学工程领域备受关注的学科发展新方向。它运用神经科学和工程学的方法来分析神经功能并为神经功能缺失与紊乱的修复提供新的解决问题的方案;而脑-机接口则是当前神经工程领域中最活跃的研究方向之一。脑-机接口是在脑与计算机或其他外部设备之间建立的直接的通信和交流通道。在脑-机接口系统中,具有特定模式的脑信号携带着受试者希望表达的意愿,计算机将接收到的脑信号转换成相应的控制命令,于是那些有运动障碍的残疾人就可以利用脑-机接口系统来实现与外界的交流与对外部设备的控制。在基于脑电信号的脑-机接口系统中,受试者产生的脑信号大致可以分为内源性（endogenous）和外源性（exogenous）两类。其中外源性的成分主要取决于外部物理刺激（视觉、听觉或触觉）的参数而与认知行为无关;而内源性成分则主要由认知行为产生而与外部的物理刺激无关。在许多情况下,脑－机接口中的瞬态诱发电位通常都同时包含着内源性和外源性两种成分。寻找新的脑－机接口模式使之能显著提升记录脑电信号中的内源性与外源性成分在脑－机接口研究中具有重要意义。本文中将介绍一种基于运动起始时刻（motion—onset）的新的脑-机接口实验范式。本文的最后还探讨了脑－机接口未来发展的趋势与展望。     

A Representational Similarity Analysis of the Dynamics of Object Processing Using Single-Trial EEG Classification

The recognition of object categories is effortlessly accomplished in everyday life, yet its neural underpinnings remain not fully understood. In this electroencephalography (EEG) study, we used single-trial classification to perform a Representational Similarity Analysis (RSA) of categorical representation of objects in human visual cortex. Brain responses were recorded while participants viewed a set of 72 photographs of objects with a planned category structure. The Representational Dissimilarity Matrix (RDM) used for RSA was derived from confusions of a linear classifier operating on single EEG trials. In contrast to past studies, which used pairwise correlation or classification to derive the RDM, we used confusion matrices from multi-class classifications, which provided novel self-similarity measures that were used to derive the overall size of the representational space. We additionally performed classifications on subsets of the brain response in order to identify spatial and temporal EEG components that best discriminated object categories and exemplars. Results from category-level classifications revealed that brain responses to images of human faces formed the most distinct category, while responses to images from the two inanimate categories formed a single category cluster. Exemplar-level classifications produced a broadly similar category structure, as well as sub-clusters corresponding to natural language categories. Spatiotemporal components of the brain response that differentiated exemplars within a category were found to differ from those implicated in differentiating between categories. Our results show that a classification approach can be successfully applied to single-trial scalp-recorded EEG to recover fine-grained object category structure, as well as to identify interpretable spatiotemporal components underlying object processing. Finally, object category can be decoded from purely temporal information recorded at single electrodes.     

Dynamics of local maxima chains in spectra of human electroencephalogram

The continuous wavelet transform was applied to the human EEG signals recorded in different states of brain activity. The dynamics of local maxima chains in the matrices of the continuous wavelet transform coefficients was studied. The typologization method was developed for local maxima chains to separate by their drift in the frequency space as well as by dynamics of their signal “energy.” The method proved to be highly informative. It was shown that it was highly sensitive to a selection of one of two responses to the test question. It is determined that local maxima chains in most cases are gradually increasing and decreasing in the frequency space and by changes in the values of their continuous wavelet transform coefficients. The functional asymmetry in local maxima chains types’ distribution is determined. The results obtained allow us to consider the types of the local maxima chains dynamics as a new phenomenon of EEG activity.     

EEG spectral characteristics at different stages of the unconscious visual set in two motivation conditions

Multichannel EEG were recorded in young healthy subjects in two series of experiments during formation, actualization, and extinction of the visual unconscious set to the perception of unequal circles under conditions of increased motivation of subjects to the result of their performance. In the first series of experiments, subjects were promised to be rewarded (a small money price) for each correct response (the "general" rise of motivation). In the second series, subjects were promised to be rewarded for correct responses only in cases when one of the circles was larger than the other one (the "directed" rise of motivation). The dynamics of the EEG spectral power derived under these two conditions was compared with similar indices obtained earlier during formation of the same set without any special motivation of subjects (control). In all experimental conditions, before the presentation of the stimuli the EEG power in the alpha range was higher in subjects with the stable set. The dynamics of changes in the alpha power at set stages was principally similar in all conditions. In all the experimental conditions, in subjects with unstable set the EEG power in the delta range was highest at the stage of set actualization. The most pronounced generalized changes in the EEG power in the theta-range during the "general" rise of motivation in subjects with stable and unstable forms of set and greater variability of the reaction time to the probe stimulus suggest that the task performance under these conditions required greater tension than under conditions of the "directed" rise of motivation.     

Influence of the Emotional Perception of a Signal on the Electroencephalographic Correlates of Creative Activity

Subjects were asked to invent as many definitions (ideas of a definition) of emotionally positive, emotionally negative, or neutral notions as possible using notions of other semantic fields. In the control task, the notions to be defined and to be used in definition were of the same or close semantic fields. The EEG was recorded during task performance. Significant differences in EEG local power (LS) and spatial synchronization (SS) were established in comparison of EEGs recorded during performance of creative tasks differing in complexity, complex creative tasks differing in emotional background (positive and negative), and tasks performed with or without emotional induction. Differences in LS and SS were most distinct in the medio- and posterotemporal areas of both hemispheres. Positive emotions increased LS and differently affected SS. Negative emotions predominantly increased SS. Analysis of self-reports of the subjects showed that both positive and negative induced emotions increased the fluency of association of notions from different semantic fields but decreased the originality of the ideas produced by a subject to define a notion.     

Post-radiation effect on the interhemispheric asymmetry in EEG and thermography characteristics

Complex analysis of EEG and thermographic parameters carried out in 10 healthy subjects and 34 patients, Chernobyl clean-up participants revealed a correlation between EEG and brain temperature changes in the baseline state and during mental arithmetic. During cognitive activity the maximal increase in the average EEG coherence and temperature shifts in healthy subjects were observed in the left frontotemporal and right parietotemporal areas. In patients changes in both parameters under study were most pronounced, the interhemispheric relations were impaired. The visual analysis revealed "flat" and "hypersynchronous" EEG types in patients. The dominant pathologic activity in the betal range indicative of mediobasal and oral brainstem lesions was characteristic of the flat EEG. This type of activity was observed in 60% of patients. In these cases, a general decrease in EEG coherence and temperature was most pronounced in the left hemisphere. The hypersynchronou EEG type (40% patients) was characterized by paroxysmal activity in the theta and alpha ranges suggesting diencephalic brain lesions. In these cases, EEG coherence and temperature were more variable; changes in the right hemisphere were significant, be it increase or decrease. Our complex approach to investigation of brain activity in different aspects seems to be promising in estimation of the brain functional state both in healthy persons and patients in remote terms after exposure to radiation. The specific hemispheric temperature changes revealed in Chernobyl patients especially during cognitive activity can be the sequels of postradiation disorders of vascular neuro-circulation. The EEG findings suggest subcortical disorders at different levels (diencephalic or brainstem) and functional failure of the right or left hemispheres in remote terms after exposure to radiation.     

Automatic classification of EEG segments and extraction of representative ones by dynamic clusters method

Use of the dynamic clusters method for automatic extraction of compressed information about recorded EEG signal is presented. The computer first divides the record into quasi-stationary segments by means of adaptive segmentation. Second, the extracted segments are classified by a method of dynamic clusters into homogeneous classes. One part of the used clustering algorithm permits to specify and draw the most typical class members, which may represent the whole studied EEG signal and may be used as input for the further phase of the automatic EEG analysis, i.e. for the classification of the whole EEG records. The above procedure was applied to a 75 sec long EEG record of anaesthetized cat intoxicated by CO.