EEG Frequency Composition Research Articles

Quantitative EEG biomarkers for STXBP1-related disorders.

EEG patterns and quantitative EEG (qEEG) features have been poorly explored in monogenic epilepsies. Herein, we investigate regional differences in EEG frequency composition in patients with STXBP1 developmental and epileptic encephalopathy (STXBP1-DEE). We conducted a retrospective study collecting electroclinical data of patients with STXBP1-DEE and two control groups of patients with DEEs of different etiologies and typically developing individuals matched for age and sex. We performed a (1) visual EEG assessment, (b) qEEG analysis, and (c) electrical source imaging (ESI). We quantified the relative power (RP) of four frequency bands (α β, θ, δ), in two electrode groups (anterior/posterior), and compared their averages and dynamics (standard deviation [SD] over time). The ESI was performed by applying the standard Distributed Source Modeling algorithm. We analyzed 42 EEG studies in 19 patients with STXBP1-DEE (10 female), with a median age at recordings of 9.6 years (range 9 months to 29 years). The δRP was higher in recordings of STXBP1-DEE (p < .001) compared to both control groups, suggesting the pathogenicity and STXBP1-specificity of these findings. In STXBP1-DEE, the δRP was significantly higher in the anterior electrode group compared to the posterior one (p = .003). There was no correlation between the anterior δRP and the epilepsy focus, age at recordings, and concomitant medications The ESI modeling of this activity showed a widespread involvement of the dorsomesial frontal cortex, suggesting a large corticosubcortical pathologic network. Finally, we identified two groups of recordings: cluster.1 with higher anterior δRP and low dynamics and cluster.2 with lower δRP and higher dynamics. Patients in cluster.1 had a more severe epilepsy and neurological phenotype compared to patients in cluster 2. The qEEG analysis showed a predominant frontal slow activity as a specific STXBP1 feature that correlates with the severity of the phenotype and may represent a biomarker for prospective longitudinal studies of STXBP1-DEE.

2200 Association between gait speed deterioration and EEG abnormalities

Abstract Introduction Physical and cognitive decline at an older age is preceded by changes that accumulate over time until they become clinically evident difficulties. These changes, frequently overlooked by patients and health professionals, may respond better than fully established conditions to strategies designed to prevent disabilities and dependence in later life. The objective of this study was twofold: to provide further support for the need to screen for early functional changes in older adults and to look for an early association between decline in mobility and cognition. Methods A cross-sectional cohort study was conducted on 95 active functionally independent community-dwelling older adults in Havana, Cuba. We measured their gait speed at the usual pace and their cognitive status using the MMSE. A value of 0.8 m/s was used as the cut-off point to decide whether they presented a decline in gait speed. A quantitative analysis of their EEG at rest was also performed to look for an associated subclinical decline in brain function. Results Results show that 70% of the sample had a gait speed deterioration (i.e. lower than 0.8 m/s), of which 80% also had an abnormal EEG frequency composition for their age. While there was no statistically significant difference in the MMSE score between participants with a gait speed above and below the selected cut-off, individuals with MMSE scores below 25 also had a gait speed&amp;lt;0.8 m/s and an abnormal EEG frequency composition. Conclusions Our results provide further evidence of early decline in older adults – even if still independent and active - and point to the need for clinical pathways that incorporate screening and early intervention targeted at early deterioration to prolong the years of functional life in older age.

Association between gait speed deterioration and EEG abnormalities.

Physical and cognitive decline at an older age is preceded by changes that accumulate over time until they become clinically evident difficulties. These changes, frequently overlooked by patients and health professionals, may respond better than fully established conditions to strategies designed to prevent disabilities and dependence in later life. The objective of this study was twofold; to provide further support for the need to screen for early functional changes in older adults and to look for an early association between decline in mobility and cognition. A cross-sectional cohort study was conducted on 95 active functionally independent community-dwelling older adults in Havana, Cuba. We measured their gait speed at the usual pace and the cognitive status using the MMSE. A value of 0.8 m/s was used as the cut-off point to decide whether they presented a decline in gait speed. A quantitative analysis of their EEG at rest was also performed to look for an associated subclinical decline in brain function. Results show that 70% of the sample had a gait speed deterioration (i.e., lower than 0.8 m/s), of which 80% also had an abnormal EEG frequency composition for their age. While there was no statistically significant difference in the MMSE score between participants with a gait speed above and below the selected cut-off, individuals with MMSE scores below 25 also had a gait speed<0.8 m/s and an abnormal EEG frequency composition. Our results provide further evidence of early decline in older adults-even if still independent and active-and point to the need for clinical pathways that incorporate screening and early intervention targeted at early deterioration to prolong the years of functional life in older age.

Longitudinal study of EEG frequency maturation and power changes in children on the Russian North

The aim of the study was to reveal longitudinal changes in electroencephalogram spectral power and frequency (percentage frequency composition of EEG and alpha peak frequency) patterns in normal children from northern Russia. Fifteen children (9 girls and 6 boys) participated in the study. The resting state (eyes closed) EEGs were recorded yearly (2005–2013) from age 8 to age 16–17 for each child. EEG frequency patterns were estimated as the percentages of waves with a 1Hz step revealed by measuring the interval durations between points crossing zero (isoline) by a curve. EEG spectral power changes were analyzed for delta (1.5–4Hz), theta (4–7.5Hz), alpha-1 (7.5–9.5Hz), alpha-2 (9.5–12.5Hz), beta-1 (12.5–18Hz) and beta-2 (18–30Hz) bands. According to the frequency composition of the EEG signals fast synchronous, polymorphous synchronous, polymorphous desynchronous and slow synchronous types of children EEG were revealed. These EEG types were relatively stable during adolescence. In these EEG types, the frequency patterns and spectral power dynamics with age had several common and specific features. Slow wave percentage and spectral power in the delta band remarkably decreased with age in all groups. Starting from the theta band the EEG types were characterized by different EEG spectral power changes with age. In fast synchronous EEG type, the theta and alpha-1 EEG power decreased, and the alpha-2 power increased in the occipital and parietal areas. The polymorphous synchronous type was characterized by increased both the alpha-1 and alpha-2 power with regional peculiarities. In the polymorphous desynchronous type spectral power in all bands decreased with age, and in the slow synchronous type, the alpha-1 power massively increased with age. Obtained results suggest predictive strength of the spatial-frequency patterns in EEG for its following maturation through the years.

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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.

Generalized background qEEG abnormalities in localized symptomatic epilepsy

Spectral features of EEG background activity were studied in patients with localized symptomatic epilepsy (LSE), with origin in the frontal or temporal lobes. Z-values of high resolution spectra and measures of the parametric ( ξ α) model of the EEG were obtained for all 10/20 System leads and were compared with those obtained in a control group. Comparisons were performed between syndromic variants of LSE and between subgroups of patients with or without paroxysmal activity in their digital EEGs (dEEG). Marked reduction of the energy in the alpha range and a mild increase in the theta range were found in the patients, unrelated to the syndromic variant of the epilepsy. These deviations from normality were widespread on the scalp and were not related to antiepileptic medication. Non-parametric testing showed a positive correlation between the magnitude of the quantitative EEG abnormalities and the amount of paroxysmal activity in the dEEG. Slowing of the mean frequency of alpha components of the spectra, an actual decrease of power in the alpha range and an increase in the theta range explained the results. The most striking finding of this paper is that focal epileptogenesis may have a generalized impact in the frequency composition of EEG.

Increases in the power spectral slope of background electroencephalogram just prior to asymmetric spike and wave complexes in epileptic patients

Moment-to-moment electroencephalogram (EEG) changes just before spike and wave complexes (SWCs) were investigated by using a non-stationary power spectral analysis in 10 epileptic patients with asymmetric SWCs. The instantaneous power spectra of background EEG were estimated for a 10-s period just before SWCs in 10 locations. The spectral shape, showing a 1 f amplitude characteristic, was assessed by the negative slope (spectral slope) of a straight line on a plot of log power versus frequency. Spectral slope significantly increased toward SWCs at locations with greater SWCs. This finding suggested structural changes in EEG frequency composition just before SWCs because of an epileptogenic process.

An EEG computerized system for the evaluation of hypnotic drugs

Digital recording of sleep EEG allows computer analysis and quantitative evaluations of sleep disorders and pharmacological effects. A system for polygraphic signal acquisition and storage, which performs a Fourier transform to compute series of spectra representing the evolution of EEG frequency composition through different sleep stages is described. The time course of spectral descriptors like relative band power is used to study the cyclic patterns of sleep and to compute the DSRI (Delta Sleep Regularity Index), a synthetic measure of sleep quality. The method is compared with conventional sleep scoring and examples of applications to normal, pathological and pharmacological conditions are shown. The topographical distribution of spectral parameters is analyzed by means of mapping techniques, allowing the detection of regional variations of EEG in specific pharmacological conditions.

Cortical EEG Frequency Composition and the Quality of Apparent Motion in Man

ABSTRACTHuman subjects were asked to rate the quality of apparent motion (beta motion) in trial‐wise presentations of stimuli. The interstimulus interval (ISI) between presentation of two adjacent light patches was varied between 10 and 90 msec. EEG activity during stimulus presentation was assessed with a frequency spectral analysis technique. Results with 10 subjects showed that high quality apparent motion was associated with faster EEG activity at short ISI, and lower frequency EEG activity at longer ISI. The results were significant at a midline occipital electrode, with a tendency in the right direction over the right occipital cortex, but not at other occipital and parietal sites. Changes were within the 8‐12 Hz frequency band. Results are interpreted in terms of a mechanism associated with components of the spontaneous EEG which serves to pace information processing within the primary visual cortex.

Perceptual correlates of variability in the duration of the cortical excitability cycle

To determine effects of cortical excitability cycle duration on human perceptual and cognitive performance, EEG frequency spectra were calculated from EEGs recorded while subjects were performing a two-flash discrimination or a duration estimation task. In the two-flash discrimination task, subjects' report of two flashes seen was associated by higher frequency EEG than when only one flash was reported. Primary EEG differences were in the alpha frequency range, about 10 c/sec. In the duration estimation tasks, correlation coefficients determined between a weighted mean frequency measure of EEG frequency composition and objective durations showed that significantly high correlations were achieved within a small frequency band (about 2 c/sec wide) near the alpha frequency. Results are related to the duration of the spontaneous cortical excitability cycle: when the cycle is shorter, discrimination threshold is reduced. Similarly, subjective duration seems to be regulated by rate of cortical information processing, which is in turn regulated by cortical excitability cycle duration.