Spectral Power Of Alpha Rhythms Research Articles

Relationship of background electroencephalogram with cognitive impairment in patients with alcohol dependence

A significant number of studies have focused on the neurophysiological basis of cognitive dysfunction among individuals with neurological and psychiatric disorders, including alcoholism. However, the neural correlates of cognitive deficits in alcohol dependence are still not clear enough.
 The purposeof the study: to identify the relationship of background electroencephalogram indicators with cognitive disorders in patients with alcohol dependence.
 Material and methods.107patients with alcohol dependence aged 30 to 60years after detoxification were examined. The background electroencephalogram was recorded with closed eyes for 2min. The values of the absolute spectral power of theta, alpha and beta rhythms were analyzed. The study of the level of Executive functioning was conducted using the Go/Nogo test. The level of spatially working memory was evaluated using the Corsi Block-Tapping test.
 Results.Data analysis revealed statistically significant correlations between the spectral power of the alpha rhythm in the occipital cortex and the number of errors per inhibitory signal (Nogo) in the Go/Nogo problem (r=0.287; p=0.025). There were also statistically significant correlations between the values of alpha-rhythm spectral power and working memory in the Corsi test in the parietal cortex (r=0.273; p=0.037), occipital cortex (r=0.316; p=0.015) and temporal cortex (r=0.359; p=0.005). There were no statistically significant correlations of beta and theta rhythms with the results of cognitive tests (p0.05).
 Conclusion.Thus, all of the above results indicate that the background EEG indicators, in particular the spectral power of alpha activity, can with a certain probability indicate violations of cognitive functioning (inhibitory control and working memory) in patients with alcohol dependence.

Quantitative electrophysiological pattern of neurodegeneration in encephalopathies of various origin

Electrophysiological characteristics of patients with encephalopathy of different etiology are presented. Pathogenic mechanisms affecting the electroencephalographic pattern and quantitative components of electroencephalogram are discussed. The aim of the study was to determine a universal quantitative electrophysiological criterion for the evaluation of neurodegenerative changes in the brain of patients with encephalopathy. We analyzed the data of anamnesis, neurological examination, laboratory tests and electroencephalograms from 389 patients with encephalopathy of post-traumatic, infectious, vascular and mixed etiology. Spectral analysis of electroencephalograms was performed and the values of relative quantitative electrophysiological criterion - the ratio of spectral power in the alpha/theta ranges at rest and during the test with hyperventilation were counted. The ratio of spectral power in the alpha/theta ranges was the lowest in patients of older age group and low - in patients with encephalopathy of infectious etiology. The ratio of the spectral power in the alpha-theta ranges in patients with post-traumatic encephalopathy was significantly different depending on the severity of the traumatic brain injury - mild or moderate/severe. We studied the possibilities of practical application of selected electrophysiological criterion - the ratio of spectral power of rhythms in the alpha-theta ranges. We counted this criterion in 150 patients with encephalopathy for the effectiveness evaluation of the neuroprotective therapy with сortexin. The chosen electrophysiological criterion had proved its effectiveness in therapy monitoring in patients with encephalopathy. In this article we demonstrated the advantages of additional neuroprotective therapy with сortexin. Increase in spectral power of alpha rhythm and decrease in spectral power of slow-wave components in the electroencephalographic pattern characterizes successful neuroprotective therapy with neuropeptides, such as сortexin.

Diurnal trend in EEG interhemispheric asymmetry in endogenous depressions

A trend in EEG interhemispheric asymmetry was studied in patients with endogenous depressions in morning and evening hours. In the morning, the spectral power of alpha rhythm particularly in the occipital cortical regions, proved to be higher than that in the evening. In the morning, the interhemispheric differences in the power of occipital alpha rhythm were leveled off while in the evening there was normalization of interhemispheric balance with the higher power of alpha rhythm in the right occipital region. Analysis of the mean coherence (mean Coh) of alpha rhythm in individual cortical regions revealed that the patients with endogenous depression had higher readings mainly in the parietal and central regions of both hemispheres and in the right temporal regions in the morning than in the evening. The occipital and posttemporal regions showed an inverse trend in the mean Coh - it was lower in the morning than in the evening.

BOLD correlates of EEG alpha phase-locking and the fMRI default mode network

Phase locking or synchronization of brain areas is a key concept of information processing in the brain. Synchronous oscillations have been observed and investigated extensively in EEG during the past decades. EEG oscillations occur over a wide frequency range. In EEG, a prominent type of oscillations is alpha-band activity, present typically when a subject is awake, but at rest with closed eyes. The spectral power of alpha rhythms has recently been investigated in simultaneous EEG/fMRI recordings, establishing a wide-range cortico-thalamic network. However, spectral power and synchronization are different measures and little is known about the correlations between BOLD effects and EEG synchronization. Interestingly, the fMRI BOLD signal also displays synchronous oscillations across different brain regions. These oscillations delineate so-called resting state networks (RSNs) that resemble the correlation patterns of simultaneous EEG/fMRI recordings. However, the nature of these BOLD oscillations and their relations to EEG activity is still poorly understood. One hypothesis is that the subunits constituting a specific RSN may be coordinated by different EEG rhythms. In this study we report on evidence for this hypothesis. The BOLD correlates of global EEG synchronization (GFS) in the alpha frequency band are located in brain areas involved in specific RSNs, e.g. the ‘default mode network’. Furthermore, our results confirm the hypothesis that specific RSNs are organized by long-range synchronization at least in the alpha frequency band. Finally, we could localize specific areas where the GFS BOLD correlates and the associated RSN overlap. Thus, we claim that not only the spectral dynamics of EEG are important, but also their spatio-temporal organization.