睡眠纺锤波在植物状态病人预后判别中的价值研究

目的:探讨脑电图睡眠纺锤波在植物状态病人预后判别中的价值。方法:在长程脑电监测下观察植物状态病人的睡眠纺锤波,与其意识恢复进行相关性分析,并预测患者意识恢复的敏感性、特异性及准确性。结果:28例患者中,12例有纺锤波,其中9例意识恢复;16例无纺锤波患者中,14例未恢复意识。纺锤波的有无与患者意识恢复有相关性,P值<0.01。脑电图睡眠纺锤波对植物状态患者意识恢复判断的敏感性(83.25%)、特异性(81.82%)、准确性(82.14%)。结论:脑电图睡眠纺锤波可较准确预测植物状态患者的意识恢复能力,可作为临床评估植物状态患者意识恢复能力的辅助方法。     

Intracerebral EEG functioning as a reflexion of the systemic brain organization in norm and pathology

The authors summarized the EEG findings and defined the nature of intercentral EEG relationships in different functional states of healthy subjects and patients with organic cerebral pathology based on coherence analysis. The EEG features typical of healthy subjects were identified: an anterior-posterior gradient of the mean coherence and the character of cortical-subcortical relationships in the anterior cerebral structures. Right- and lefthanded subjects showed the frequency and regional differences in EEG coherence, which reflected, mainly, specific intracortical relationships. Development and regression of pathologic signs in right- and lefthanded patients with organic brain lesions are thought to be determined by these differences. As distinct from cortical pathology, lesions of regulatory structures (diencephalic, brainstem, and limbic) were shown to produce more diffuse changes in intercentral relationships with a tendency to reciprocity. Intercentral relations, including their interhemispheric differences, varied with changes in the functional state of healthy subjects (increase and decrease in the level of functioning). A certain time course of changes in intercentral relationships was also revealed in patients with organic brain lesions during recovery of their consciousness and mental activity. Changes in the dominance of activity of individual regulatory structures are considered to be one of the most important factors that determine the dynamic character of EEG coherence.     

Influence of Short-Term Relaxation on the Organization of the Brain Electrical Activity of Young Schoolchildren in the State of Quiet Wakefulness

Relaxation-induced changes in characteristics of the functional state of the nervous system (EEG parameters and electrodermal resistance (EDR)) were studied in 30 schoolchildren aged 9–10 years. A multichannel EEG was recorded from the occipital, parietal, temporo-parieto-occipital, central, and frontal areas of both brain hemispheres in three test conditions: quiet wakefulness, R, and recovery of the initial state. Simultaneously, the EDR was monitored. EEG amplitude spectra and coherence were calculated. Prior to and after relaxation, a cognitive test to determine the extent of short-term auditory verbal memory was performed. While changes in the EDR were reversible, relaxation-induced changes in the EEG parameters persisted after relaxation in many subjects. Changes in EEG coherence between distant derivations were most stable. Since short-term auditory verbal memory improved after relaxation, the postrelaxation changes in the EEG parameters were considered to reflect positive changes arising in the brain function and increasing the efficiency of cognitive processes.     

Intercentral EEG relationships in regressive and chronic post-traumatic Korsakoff syndrome.]

Dynamic EEG study of patients with posttraumatic Korsakoff's syndrome (KS) with the application of complex analysis methods revealed a complicated pathological structure of the intercentral relations of cortical electrical activity. The interhemispheric EEG coherence between symmetrical frontal cortical areas are sharply reduced, while the intrahemispheric coherence are increased in comparison with the normal values. The proposed technique of segregation of statistically homogeneous spectro-coherent characteristics made it possible to reveal the earlier intercentral EEG relations formed by stable and variable coherence spectra. The structure formed by the stable and variable coherence spectra in KS differs from that reflected in the mean coherence levels. During the KS regression, the EEG coherence between the right and left frontal areas increased to the normal level, and the variable spectra are revealed. In the chronic KS syndrome, the pathological intercentral relations persist, while the variable relations in the frontal areas are absent. A reduction of pathologically decreased intrahemispheric coherence selectively revealed in the right hemisphere during the KS regression and formation of variable relations in this hemisphere point to a leading role of the right hemisphere in development of compensatory processes in KS. The reciprocal relations between the intra- and interhemispheric coherence and coherence dynamics in the theta rhythm suggest that pathological activity in the basal diencephalic structures plays an important role in formation of the pathological EEG pattern in KS.     

EEG markers of the stabilotraining effect during the rehabilitation of patients with posttraumatic Korsakoff’s syndrome

Nine patients with posttraumatic Korsakoff syndrome (KS) were examined before and after a rehabilitation course of feedback stability training (ST) using EEG, posturographic and clinical tests (with the FIM and Mayo Portland scales used for estimation). During 7 to 12 sessions, the patients tried to perform static and motor tasks. A group of 18 healthy subjects were examined to provide standard parameters. The results demonstrated a disturbed spatiotemporal EEG pattern in patients with KS before ST in the form of a reduced coherence for short derivation pairs (intrahemispheric, interhemispheric, and diagonal ones) in frontal and parietooccipital areas. Analysis of specific EEG rhythms demonstrated the maximum decrease in coherence in the α band (with the aforementioned regional specificity) and for long diagonal pairs (between the left frontal and right parietooccipital areas). The ST course was accompanied by KS regression (according to clinical scales and posturographic study); an original increase in EEG coherence, especially that of α waves, was recorded in the occipitoparietal and central frontal areas of the right hemisphere; a subsequent increase in coherence of the frontal areas in both hemispheres was observed. Late after the ST course, further positive changes were characteristic of the EEG spatiotemporal pattern. However, comparison with standard data suggested incomplete recovery of various coherence parameters: hypertrophied coherence in intrahemispheric pairs and still reduced values in interhemispheric derivations. This EEG pattern suggested incomplete KS regression, which was confirmed by clinical data.     

The reorganization of the electrical activity of the human brain during the depression of consciousness (comatose states)

To study the problem of consciousness an original structural-functional approach has been applied with the use of possibilities of spectral-coherent EEG analysis in evaluation of human brain functional state together with the specificity of the cerebral coma having local focal belonging. It is revealed that the most informative signs for characteristics of consciousness state are peculiarities of reconstruction of intercentral relations of the electrical brain processes: decrease of mean levels of the EEG coherence at progressive development of coma; staged approach to relative norm at regressive course of comatose state and recovery of consciousness; their stability on the low level at prolonged coma; increase in low or high (above optimum) frequencies band at neighbouring with coma states of consciousness. It may be considered that one of the necessary conditions of normal state of consciousness is preservation of the optimum level of correlation of electrical brain activity alongside with frequency-regional specificity of the EEG coherence spectrum. Any deviation from the optimum is unfavourable condition for normal course of cerebral reactions because of the disturbance of intercentral connections mosaic necessary for their realization.     

Bedside Evaluation of the Functional Organization of the Auditory Cortex in Patients with Disorders of Consciousness

To measure the level of residual cognitive function in patients with disorders of consciousness, the use of electrophysiological and neuroimaging protocols of increasing complexity is recommended. This work presents an EEG-based method capable of assessing at an individual level the integrity of the auditory cortex at the bedside of patients and can be seen as the first cortical stage of this hierarchical approach. The method is based on two features: first, the possibility of automatically detecting the presence of a N100 wave and second, in showing evidence of frequency processing in the auditory cortex with a machine learning based classification of the EEG signals associated with different frequencies and auditory stimulation modalities. In the control group of twelve healthy volunteers, cortical frequency processing was clearly demonstrated. EEG recordings from two patients with disorders of consciousness showed evidence of partially preserved cortical processing in the first patient and none in the second patient. From these results, it appears that the classification method presented here reliably detects signal differences in the encoding of frequencies and is a useful tool in the evaluation of the integrity of the auditory cortex. Even though the classification method presented in this work was designed for patients with disorders of consciousness, it can also be applied to other pathological populations.     

Changes in aesthetic appearance and intelligibility of speech after partial glossectomy in patients with Down syndrome

Eight patients with Down syndrome, aged 9 years and 10 months to 25 years and 4 months, underwent partial glossectomy. Preoperative and postoperative videotaped samples of spoken words and connected speech were randomized and rated by two groups of listeners, only one of which knew of the surgery. Aesthetic appearance of speech or visual acceptability of the patient while speaking was judged from visual information only. Judgments of speech intelligibility were made from the auditory portion of the videotapes. Acceptability and intelligibility also were judged together during audiovisual presentation. Statistical analysis revealed that speech was significantly more acceptable aesthetically after surgery. No significant difference was found in speech intelligibility preoperatively and postoperatively. Ratings did not differ significantly depending on whether the rater knew of the surgery. Analysis of results obtained in various presentation modes revealed that the aesthetics of speech did not significantly affect judgment of intelligibility. Conversely, speech acceptability was greater in the presence of higher levels of intelligibility.     

The reflection of different levels of the regulation of human brain activity in spectrally coherent EEG parameters]

On the basis of clinico-anatomo-electroencephalographic studies it was shown, that in early terms of cerebral trauma, at gross disturbances of the cortical functions and safety in some cases of only vital regulation, the parameters of the EEG stability or variability are of distinct information value for estimation of the functional state of patients. It was established, that changes of stability of the frequency, power, and coherent EEG characteristics correlate with different parameters of changes of the structural-functional brain organization. At this stage the greatest connection with the disease outcome reveals the EEG coherence parameters of the cortical symmetrical points reflecting the state of predominantly median formations and general brain reactions to traumatic action. In the process of restoration of disturbed neuromental functions priority prognostic significance is acquired by parameters of intrahemispheric coherence as well as by frequency-regional properties of interhemispheric asymmetry of coherence of the brain electrical processes, characterizing functional features of the lesion focus.     

Functional organization of the cortex of the large hemispheres during voluntary movement performance: Age aspect

The method of estimation of the coherence (Coh) function values of EEG rhythmic components disclosed the specific features of functional associations of cortical regions during the performance of voluntary graphic cyclic movements under usual and unusual conditions. A significant increase in the Coh function values of the α-rhythm was observed both in the contralateral hemisphere and the symmetrical central and parietal cortical regions in adult subjects during right-hand movement performance with open eyes (usual conditions); in this case the resulting functional associations included motor zone and cortical regions responsible for visual information analysis and perception. During right- and left-hand movement performance with closed eyes (unusual conditions), the mature-type functional organization had a bilateral character with interrelated activity focused in the frontal regions that clearly demonstrated the function of these structures during formation of new motor programs. The significant changes in cortical mechanisms of voluntary graphic movements were disclosed in young 7- to 8- and 9- to 10-year-old schoolchildren.     

Spectral and coherence EEG analysis of rats differing in the level of seizure readiness

The resting EEGs of several brain structures (motor and visual cortex, caudate nucleus and intralaminar thalamic nuclei) were submitted to spectral and coherence computer analyses in two rat strains. Genetically predisposed to convulsive state KM rats were shown to differ from nonpredisposed Wistar rats in EEG spectral properties. KM rats EEG pattern was characterized by increase of low frequencies (1-2 Hz) power and decrease of faster activity (5-12 Hz) power in cortical spectrograms as well as by decrease of caudate nucleus EEG absolute power. The coherence value between cortical or subcortical structures at below 4 Hz was intensified in KM rats. Reinforcement of cortical auto-oscillating properties manifested by ECoG synchronization in cortical-thalamic resonance interaction as well as weakening of striatal inhibitory system may constitute neurophysiological mechanisms of enhanced convulsive readiness. The probable role of mediator imbalance in these mechanisms is discussed.     

Optimal structure of the connections of the electrical processes in the human cerebral cortex and its disorders in changes of state

In this paper the data are analyzed on the human EEG investigation. Significance is shown of parameters of correlative and spectral-coherent EEG functions for the estimation of the brain functional state of healthy people and patients with local cerebral lesions. In the norm, the parameter of the mean coherence is stable, its characteristics correspond to the optimum cortical tone, the most favourable for the performance of the cortical functions. In healthy people unstable, individual, different in different cortical areas changes of the spectrum details, coherence and phases reflect local processes, taking place at the optimum mean level of the coherence and form the cortical mosaic. These two sides of the intercentral relations of the electrical processes (optimum level of coherence and dynamic mosaic of connections of separate rhythms) reflect the most favourable conditions of the nervous processes development. In the brain pathology, different forms are noted of deviations from the system of intercentral relations and levels of coherence of cortical electrical processes.     

Electroencephalographic markers of the spontaneous recovery of the vertical posture in patients with consequences of traumatic brain injury

Nine patients (mean age, 23.6 ± 3.15 years) with a severe traumatic brain injury (TBI) associated with a loss of the ability to maintain vertical posture were enrolled in a comprehensive clinical and electroencephalographic study during the spontaneous recovery of vertical posture (VP). The patients were divided into three groups according to their functional deficit assessed on the international MPAI, FIM, and MMSE scales, which was determined by the severity of the TBI. The EEG data were compared to those of ten healthy subjects (mean age, 22.8 ± 0.67 years). In patients with a moderate impairment of the brain and a rapid recovery of VP (over two weeks), a change in the sitting position revealed EEG signs similar to reactive EEG restructurings of healthy individuals during the maintenance of VP in the form of a predominant EEG coherence increase in the right hemisphere for most of the rhythm bands; however, at this stage of VP recovery, the EEG restructurings retained pathological signs. In patients with a more severe functional deficit, spontaneous recovery of VP was accompanied by hyperreactive EEG restructurings for all rhythm bands without regional specificity. This finding showed up irrespective of the lateralization of the brain injury, which could be considered as a marker of positive dynamics of VP recovery. In patients with the most severe impairment and functional deficit and long-term (more than three months) absence of spontaneous VP recovery, the absence of reactive EEG restructurings was revealed in their passive verticalization, which could be used as a marker of negative prognosis.     

Indices of Coherence of EEG Rhythms in the Course of Cognitive Activity as Markers of Creative Thinking: Gender Specificity

According to the results of psychological testing, persons aged 18 to 21 years were divided into four groups, women and men with low and high productivity of divergent (creative, nonroutine) thinking (n = = 18 to 23). Results of EEG recording (19 leads) were used for calculation of the coherence coefficients for oscillations of the delta, theta, alpha1, alpha2, alpha3, beta, and gamma frequencies in lead pairs and estimation of integral indices of coherence within the anterior and posterior cortical regions and between these zones (interaction coefficients, IC1-IC3, respectively). EEG was recorded in the resting state and in the course of resolving convergent- and divergent-type cognitive test tasks. It was found that, during the performance of tests of both types, men with a higher productivity of divergent thinking demonstrated significantly higher values of IC1 (that characterizes the coherence in associative linkages within the anterior cortex) for oscillations of all EEG frequency ranges compared with the respective estimates for “low-creative” men. Similar increments were typical of the IC2 values for low- and midfrequency EEG rhythms (delta, theta, and alpha). At the same time, values of the “interregional” IC3 for theta, beta, and gamma activity in “high-creativity” men were significantly lower. In women of both groups (low and high creativity), such specificity of the IC1-IC3 patterns was practically not observed, i.e., the respective aspect demonstrated clear gender specificity. The sex of the subjects and type of the performed cognitive tests could not be considered factors significantly affecting the calculated absolute IC values. The observed specificities of integral coherence indices are probably associated with different strategies of the performance of cognitive tasks in men and women. Our findings allow us to believe that the above interrelations between integrated coherence indices can be used as EEG markers of high productivity of divergent thinking in men. The more flexible strategies of thinking in women are probably related to more variable neurophysiological cortical mechanisms (compared with those in men), and this type of organization is not clearly reflected in the pattern of intracortical interactions estimated by coherence indices.     

Frontal bilateral synchronous theta waves and the resting EEG coherence in children aged 7–8 and 9–10 with learning difficulties

The resting state cortical functional connectivity was studied in children of 7–8 (N = 29) and 9–10 (N = 23) years with learning difficulties whose EEG showed the frontal bilateral synchronous theta waves (FTW) and in the control children of 7–8 (N = 32) and 9–10 (N = 16) years who did not experience school difficulties and whose EEG did not show signs of abnormality. The functional connectivity was estimated in the θ, α₁, α₂, and β₁ frequency bands via measuring the coherence for the resting EEG that was free from any abnormal patterns. Compared to control children, there was a reduction in the strength of the functional coupling between the frontal and anterior temporal cortices found predominantly in the left hemisphere of FTW children. The relative weakness of the coupling between the frontal cortex and the other cortical areas was more pronounced in children of 7–8 than in children of 9–10 years. These between-group differences were unaffected by the frequency band or gender factors.     

Impairment of space-frequency parameters of EEG coherence during cognitive performance (consequences of Chernobyl accident)

Changes in frequency and space parameters of the EEG coherence evoked by cognitive performance were analyzed in 13 healthy subjects and participants of the Chemobyl clean-up. In healthy subjects, the EEG coherences in the alpha and beta frequency bands were significantly increased during arithmetic count and during visuospatial performance. Each test was characterized by regionally-specific features. Chemobyl patients demonstrated a global decrease in the EEG coherence predominantly in the alpha and beta frequency bands, especially in the frontal cortical areas. Patients with various pathological EEG patterns demonstrated specific impairment of EEG parameters. In patients with a "flat" EEG pattern, the EEG coherence predominantly decreased in the frontal associative areas, especially during arithmetic calculation. In patients with a "hypersynchronous" EEG pattern, the decrease in the EEG coherence was most pronounced in the parietal associative areas, especially during the visuospatial performance. The revealed impairments of the EEG coherence reactivity may be a reflection of disorders of the intracortical and corticosubcortical interaction and can result from the remote postradiation brain atrophy, especially, of cortical structures.     

Role of the Visual Afferent Stream in Recovery of the Postural Control in Different Periods after Craniocerebral Injury

A comprehensive posturographic (PG), electroencephalographic, and clinical examination was performed during rehabilitation in 17 patients (mean age 27.5 ± 7.4 years) who had suffered a severe craniocerebral injury (SCCI). Of these, nine were examined soon after the SCCI and eight, in the period of remote consequences of the SCCI. The patients were compared to a control group of 18 healthy subjects (mean age 27.8 ± 12.2). The PG studies showed that, in the healthy subjects, the amplitude of sway of the common center of pressure (A_CCP) in the absence of the visual control was higher than with the eyes open. The A_CCP was higher in the sagittal than in the frontal plane and decreased during optokinetic stimulation. In the control group, rhythmic photostimulation produced a local increase in interhemispheric EEG coherence in symmetrical occipital and parietal cortical areas. In the patients examined early after the SCCI with the eyes open, the A_CCP was higher than in the healthy subjects, especially in the frontal plane. The A_CCP did not decrease in the Romberg posture and increased during optokinetic stimulation. In these patients, rhythmic photostimulation was accompanied by a generalized increase in mean interhemispheric EEG coherence as compared to the resting level. In the remote period after the SCCI, the PG and EEG responses to a decrease or an increase in the visual afferent stream proved to be inverted: the patients stood better with the eyes closed than with them open and photostimulation produced a decrease in EEG coherence in the occipitoparietal areas of the cortex. The results confirmed a greater efficiency of rehabilitation in the early period after the SCCI. Thus, specific PG and EEG reactions were observed in the SCCI patients at different stages of recovery. The generalized reactivity and “infantile” features of the EEG and PG rearrangements characteristic of the early period after the SCCI were considered to be a favorable prognostic sign for the recovery of the integrative brain activity and postural control of a patient. The inversion of the reactions in the remote period after the SCCI testified to limited possibilities of the recovery of the impaired functions and was indicative of a pathological type of compensatory rearrangements.__________Translated from Fiziologiya Cheloveka, Vol. 31, No. 4, 2005, pp. 5–13.Original Russian Text Copyright © 2005 by Zhavoronkova, Maksakova, Shchekut’ev.     

Complexity of Multi-Channel Electroencephalogram Signal Analysis in Childhood Absence Epilepsy

Absence epilepsy is an important epileptic syndrome in children. Multiscale entropy (MSE), an entropy-based method to measure dynamic complexity at multiple temporal scales, is helpful to disclose the information of brain connectivity. This study investigated the complexity of electroencephalogram (EEG) signals using MSE in children with absence epilepsy. In this research, EEG signals from 19 channels of the entire brain in 21 children aged 5-12 years with absence epilepsy were analyzed. The EEG signals of pre-ictal (before seizure) and ictal states (during seizure) were analyzed by sample entropy (SamEn) and MSE methods. Variations of complexity index (CI), which was calculated from MSE, from the pre-ictal to the ictal states were also analyzed. The entropy values in the pre-ictal state were significantly higher than those in the ictal state. The MSE revealed more differences in analysis compared to the SamEn. The occurrence of absence seizures decreased the CI in all channels. Changes in CI were also significantly greater in the frontal and central parts of the brain, indicating fronto-central cortical involvement of “cortico-thalamo-cortical network” in the occurrence of generalized spike and wave discharges during absence seizures. Moreover, higher sampling frequency was more sensitive in detecting functional changes in the ictal state. There was significantly higher correlation in ictal states in the same patient in different seizures but there were great differences in CI among different patients, indicating that CI changes were consistent in different absence seizures in the same patient but not from patient to patient. This implies that the brain stays in a homogeneous activation state during the absence seizures. In conclusion, MSE analysis is better than SamEn analysis to analyze complexity of EEG, and CI can be used to investigate the functional brain changes during absence seizures.     

EEG characteristics determining the quality of subsequent recognition of visual images

Recognition of noisy pictures of Arabic numerals was accompanied by an increase in EEG coherence in the frontal cortical regions, especially in the left hemisphere, and between the frontal and occipital areas in both left and right hemispheres. Coherence values decreased in the temporo-centro-occipital areas of both hemispheres. A correlation was found between the coherence pattern in the prestimulus period and the quality of subsequent activity. Correct recognition was preceded by left-side asymmetry of the EEG coherence. Before erroneous recognition, EEG coherence levels were higher than before a correct response, and the increase in coherence was widely generalized over the cortex (especially in the Δ, ?, and α₁ frequency bands). The frequency of expression of an increased integral EEG coherence was higher before erroneous recognition than before a correct response. These changes in coherence were symmetrical.     

Spectral analysis of the human EEG in acutely developing foci of irritation at the diencephalic and brain stem levels

The dynamic study of EEG spectra and coherence in 52 patients in early period after tumor ablation at the diencephalic (27 patients) and brainstem (25 patients) levels with favourable (24 patients) and lethal (28 patients) outcomes revealed a dependence of their changes on the reversibility or irreversibility of pathological irritation of these brain levels. At regressively developing foci and retained compensatory mechanisms characteristic changes of EEG relations were seen in the central cortical areas, i. e. in cortical projection zone of the nonspecific thalamic pathways. The changes observed consisted of EEG synchronization in the band of 7 cps and sharp coherence increase while changes of EEG correlations in other cortical areas were unsimilar. Gradual EEG normalization with alpha-rhythm restoration passed through the stage of sigma-rhythm and slow sleeplike waves which indicated the safety of brainstem-subcortical hypnogenic systems. In patients with destructive foci at the diencephalic and brainstem levels, i. e. under conditions of brain functioning similar to "cerveau isolé" and "encephale isolé",--a general coherence decrease and EEG synchronization in the band of 5 cps, or generalized slow, monomorphic oscillations were observed.