Electrophysiological Correlates of Major Depression Disorder with Anxious Distress in Patients of Different Age Groups

The electrophysiological correlates of major depression disorder with anxious distress in patients of different age groups have been investigated. The spectral characteristics of 19-channel background EEG were analyzed and the power spectra recorded with the eyes closed vs. eyes open in 64 patients with anxiety–depressive disorder and in 194 healthy subjects were compared. The subjects were divided into the two age groups: 18–39 and 40–76 years old. The spectral parameters were calculated for 5 main EEG frequency bands: θ (4–8 Hz), α (8–12 Hz), β₁ (12–20 Hz), β₂ (20–30 Hz), and γ (30–40 Hz). The most statistically significant differences between the groups were found in the α, β, and γ bands. Lower values of spectral power of the α rhythm in occipital areas and the higher values of spectral power of the β and γ rhythms in the frontocentral region were recorded in the group of 18-to-39-year-old patients with the eyes closed. Higher values of spectral power of the β rhythm in the fronto-central region and in the left temporal lobe were recorded in the group of 40-to-76-year-old patients with both the eyes closed and the eyes open. The higher β-activity in the fronto-central regions in both groups of patients may be caused by increased excitability of the cerebral cortex and decreased activity of inhibitory processes. Increased activation of the left temporal lobe in older subjects is probably associated with the severity of anxiety symptoms and may be a distinctive marker of mixed anxiety and depressive disorder. The lower values of α-power revealed only in the group of younger subjects are probably associated with age-related reorganization of EEG in older subjects.     

Brain bioelectrical activity at a high anxiety level in humans

Brain bioelectrical activity was studied in 38 and 34 subjects with high and low levels of anxiety, respectively, by means of toposelective mapping of EEG spectral power and recording of P300 endogenous event-related auditory evoked potentials (EPs). Analysis of EEG spectra demonstrated, in the subjects with a high level of trait anxiety, a higher power of β₁ oscillations in the central-parietal areas of both hemispheres and the occipital area of the right hemisphere, as well as a higher power of θ and α oscillations in the frontal areas of both hemispheres and the central-parietal area of the left hemisphere. The occipital-frontal gradient of the spectral power of these rhythmic EEG components was altered in subjects with a high level of trait anxiety. Comparison of P300 cognitive auditory EPs in the subjects with high anxiety and in the control group showed that, in the former, the P300 EP amplitude and the habituation distortion (dishabituation) of the P300 EP amplitude were significantly higher in both hemispheres. This indicates that, at a high level of anxiety, the active directed attention was disturbed, which is confirmed by the results of neuropsychological examination, demonstrating reduced selectivity, concentration, and stability of attention in the Münsterberg test and Schulte’s test. The results of electrophysiological examination suggest that the malfunction of regulatory brain modulating systems is an important neurophysiological mechanism of attention pathology and disturbed adaptation in subjects with a high level of trait anxiety.     

Interrelations between EEG Parameters and Personality Characteristics in Parkinsonian Patients

We studied a number of EEG parameters and indices of personality characteristics (evaluated with the use of the MMPI questionnaire) in sixty 44- to 73-year-old patients with Parkinson's disease (PD). According to the intensity of the symptoms, they were classified into groups 1 and 2, with an initial or moderate level of disease manifestation. In group-2 patients, the powers of the - and -range rhythms were greater, as compared with those in group 1. This was combined with higher indices in scales 2 (depression, D), 8 (individualism, Sc), and 0 (introversion/extraversion, Si). A clear correlations between the EEG parameters and indices of personality structure were found. There were positive correlations between the normalized power of ₂-rhythm and values of a few MMPI scales: 1 (supercontrol, Hs), 2 (depression, D), 4 (impulsivity, Pd), 7 (anxiety, Pt), 8 (individualism, Sc), and 0 (introversion/extraversion, Si). We also found negative correlations between the frequency of -rhythm and indices of supercontrol and anxiety scales. Correlations between different EEG parameters and MMPI scale indices depended on the level of disease manifestation. Our results allow us to assume a certain generality of the neurophysiological mechanisms determining modifications of the integral electrical activity of the brain and formation of individual psychological characteristics in parkinsonian patients.     

Specific features of the oscillatory brain activity during the final stage of creative problem solving in young and elderly subjects

The neurophysiological mechanisms underlying retention of creative potential during aging are still poorly studied. Previously, we have identified age-related changes in the temporal dynamics of brain activity and the speed of creative problem solving at its initial stage, suggesting that younger and older subjects used different strategies. These differences in strategies may also be observed at the final stage of problem solving. Therefore, we have studied the pattern of temporal changes in the EEG spectral characteristics (event-related spectral perturbation, ERSP) in younger (N = 89, 22.1 ± 3.2 years) and older (N = 90, 64.9 ± 6.7 years) age cohorts during 600 ms before the preparation to motor response, which indicates that solution is found. The general and ageand sex-related features of the oscillatory brain activity at the final stage of problem solving were revealed. All subjects displayed statistically significant EEG temporal dynamics associated with a reduction of power reactivity of rhythms prior to the response. The age-related differences included more pronounced ERSP frontal–parietal gradient in the θ frequency range and lower ERSP values in the β frequency range in elderly subjects as compared with the younger individuals. The most pronounced age-related differences in the β₁ rhythm were observed in the posterior cortex. The age-related differences in the α₃ frequency range were mediated by the sex factor: lateral differences were pronounced only in young men, and the coefficient of hemispheric asymmetry in this group differed significantly from that in older men and younger women. These data reflect the changes in EEG that were associated with the evaluation of creative idea, making a decision about completion of the search, and intention to make a motor response that indicates that solution is found.     

The reflection of different aspects of brain activation in the electroencephalogram: Quantitative electroencephalography of the states of rest with the eyes open and closed

The rest states with the eyes open (RSEO) and closed (RSEC) were subjected to quantitative EEG study as states similar in the pattern of mental activity and subjective assessments but different in the EEG pattern. The mean values of the spectral power and EEG coherence function were compared in 74 subjects for the following bands: Δ, ?, α₁, α₂, β₁, β₂, and γ. Upon the transition from the RSEC to the RSEO, the EEG local power significantly decreased over the whole cortex for the α, ?, and β bands. A simultaneous decrease in the EEG power in all the bands (including β and γ) was most pronounced (as judged by relative changes and tests of significance of difference) in the parietooccipital derivations immediately related to the cortical zones where an increase in the neuronal activity upon opening the eyes is most probable. A significant increase in the EEG power was observed only for the γ band in frontal derivations F ₃ and F ₄. Significant differences in the mean EEG coherence in the RSEO-RSEC comparison were present in many derivation pairs, especially in the α₂, β₁, β₂, and γ bands. For each of these bands, the number of differences determined on the basis of Fisher test was more than 70% of the maximum possible number. In the overwhelming majority of cases, the coherence was lower in the RSEO; however, in the caudal cortical zones, a higher coherence in the α₁, ?, and Δ bands in the RSEO was rather typical. The results confirmed that the two states under study differ in a number of averaged EEG parameters with high statistical significance and may be used as reference states during performance of tasks with the eyes open and closed, respectively. The differences between the RSEC and the RSEO may be caused by the fact that the RSEC is a functional state oriented predominantly to the analysis of internal information (internally oriented), and the RSEO, predominantly to the analysis of information coming from the outside (externally oriented). The pattern of the observed EEG differences points to a combination of effects both localized in the visual zone and reflecting changes in the network cortical activity, i.e., simultaneous, although nonuniform, changes over all the main zones of the cortex. Comparison of the results with published estimations of differences in the local cerebral blood flow (ICBF) between the RSEO and the RSEC shows that increase in the ICBF may be associated with a local decrease in the EEG spectral power in any frequency band, including the high-frequency β and γ bands, or several frequency bands simultaneously.     

Relationships between the EEG θ- and β-parameters and heart rate variability during human cognitive performance

We studied the dynamics of spectral coherence characteristics of the EEG θ-, β₁-, and β₂-activity and the heart rate variability (HRV) in subjects performing cognitive tests. We found an association between the HRV parameters in the process of cognitive activity and the coherence of potentials in the EEG θ-, β₁-, and β₂-bands. The heart rate parameters in the baseline state and during the test performance best correlated with the levels of the right-hemispheric coherence of potentials in the θ-, β₁-, and β₂-bands of the baseline EEG (eyes closed). The higher coherence levels corresponded to lower values of the mean time of RR intervals (RRNN), coefficient of variation (CV), total power (TP), the power of the high-frequency (HF) and low-frequency (LF) components in the HRV spectrum. During the performance of the test, higher coherence values in the EEG θ-bands with the focus in the right temporal lead corresponded to higher LF/HF values reflecting the predominance of sympathetic effects on heart rate.     

The influence of reward on the performance of verbal creative tasks: Behavioral and EEG effects

The goal of this study was to compare the effects of the verbal instruction (IN1) that stimulated originality and of monetary reward (IN2) on the efficiency of performing a verbal creative task. The EEG patterns were also compared on the basis of mapping the bioelectric potential power within the frequency range of 4 to 30 Hz. Right-handed students (10 men and 10 women) participated in the experiment. The originality of the solution improves if a monetary reward is expected. In contrast to IN1, the promise of a monetary reward caused a global increase in task-related synchronization of bioelectric potentials in the θ₂ band. Hemispheric asymmetry of the power of the θ₁, θ₂, and α₂ rhythm grows with higher values in the right hemisphere. These changes in response to IN2 were in the background EEG, which testifies that an overall increase in hemispheric asymmetry induces a preparatory state after the promise of monetary reward. Specific changes in regional brain activity were at the β₂-rhythm frequency. In all posterior derivation, except for the frontotemporal ones, the power of the β2 rhythm decreased in response to IN2 in contrast to IN1. The rewardinduced changes in EEG were characteristic of men to a greater extent. An increase in the θ₂-rhythm asymmetry and the power of the α rhythm was observed only in men in response to a monetary reward. Our results suggest that the promise of monetary reward is favorable for creative thinking and original solutions. Gender differences of changes in the power of bioelectric potentials suggest that the neurophysiological mechanisms of creativity are different in men and women.     

Effect of swinging on EEG of rats of juvenile age in the wakefulness state

Simultaneous recording of the EEG activity of superficial cortical and deep (caudate nucleus, dorsal hippocampus, anterior hypothalamus) brain parts has been performed for the first time after a 2-h swinging of frequency of 0.2 Hz in Wistar rats of juvenile age. Swinging was produced on a 4-bar parallel swing. Using a Neuron-Spectre electroencephalograph and a Diana program, normalized power spectra of wave EEG components, synchronization coefficients, and coefficients of cross-correlation between bioelectrical potentials of various brain structures were determined. After a 2-h swinging, the mean value of normalized power of slow waves of δ-diapason in hypothalamus and hippocampus was found to increase statistically significantly, while normalized power of fast waves of α-and β₁-diapasons in hippocampus decreased (p < 0.05). A statistically significant increase of synchronization coefficient was observed in hypothalamus and hippocampus. Changes of coefficients of cross-correlation between hypothalamus and hippocampus and other brain strictures were of the oppositely directed, individual character. In the parietal occipital brain cortex and in caudate nucleus, the changes of the EEG spectral composition also were of individual character. The obtained results on the whole correspond to data about an enhancement of the EEG low-frequency rhythms at swinging and agree with the resonance hypothesis of motion sickness.     

Neuropsychophysiological correlates of reactive depression

To justify neurophysiological correlates of depressive disorders, the spetral parameters of EEG, peak latencies of the “late” components of auditory cognitive evoked potentials, and latencies of sensorimotor reactions in middle age and elderly patients (aged 53–72 years) during therapy of prolonged psychogenic depressive reaction (F43.21 according to ICD-10) have been studied. Initial depression severity was associated to the EEG signs of decreased functional state of the anterior areas of the left hemisphere and increased activation of the right hemisphere (especially, its temporal areas). Pronounced improvement of clinical state under the affect of psychopharmacotherapy was accompanied by acceleration of the sensorimotor reactions, a decrease in peak latencies of the “late” components (P2, N2, and P3) of auditory cognitive evoked potentials and associated with the EEG signs of improvement of functional state of the posterior areas of the brain, an enforcement of inhibitory processes in the right hemisphere (especially, in its frontal, central, and temporal areas) and more pronounced activation of frontal areas of the left hemisphere. The data are in good agreement with the concept on the systemic character of impairments of brain functioning in depression, as well as on the preferential role of the left hemisphere in control of positive emotions and the right one, of negative emotions.     

Differences in brain activity during olfactory testing of female body odors between young men with and without sexual experience

Olfactory testing was performed in two groups of young men aged 18–22 years with and without sexual experience. Multichannel EEG was recorded at rest and upon the presentation of 45 natural body odors of young women in different phases of the menstrual cycle. The odors were either intact or mixed with J’Adore L’Absolu perfume (Christian Dior) with or without a female pheromone. Changes in spectral power within narrow frequency ranges in response to olfactory stimulation were estimated by multivariate analysis of variance. It was found that background electrical activity of the brain in young men with regular sex life had lower spectral power in all frequency ranges. The EEG responses to the intact olfactory stimuli in all young men were associated with a decrease in spectral power in the majority of the frequency ranges and especially in the θ₂ and high- and low-frequency α rhythms. Presentation of female odors masked with a perfume resulted in bidirectional EEG responses; i.e., the spectral power in the θ₁ and β₁ ranges increased or decreased depending on the sexual experience of men and the menstrual cycle phase of a female donor as compared with an intact odor. The comparison of the EEG responses to intact or perfume-masked odors showed that individual odor remains dominant.     

Neurophysiological indices of CNS plasticity in the course of treatment of head trauma in adolescents

Using the methods of quantitative EEG analysis and cognitive evoked potentials, we investigated delayed consequences of head trauma (HT) after nootropic therapy with cerebrolysin. The study was performed in 30 12-to 19-year-old adolescents who had had severe HT with brain contusion one to five years prior to the study and manifested asthenic symptoms. During the study, they underwent treatment with 30 daily intramuscular injections of cerebrolysin at a dose of 0.1 ml/kg body weight. A positive effect on the functional state of the brain was found in 77% of patients. It was expressed as the appearance of the occipital α rhythm in the EEGs, an increase in the EEG spectral power, normalization of frequency parameters of the α rhythm, a decrease in the power spectrum of the low-frequency θ and δ EEG activity, and shortening of the P300 peak latency. These changes were associated with an improvement of the general clinical state and the psychometric indices of attention and memory in the patients.     

Analysis of EEG characteristic at early stages of depression using method of independent components

Independent Component Analysis (ICA) was used for 19-channel resting EEG analysis 111 patients at early stages of depressive disorder and 526 age-matched healthy subjects. Comparison of independent components power spectra in depressed patients and healthy subjects in two states: Eyes closed and Eyes open, has revealed significant differences between groups for three frequency bands: Theta (4-7.5 Hz), Alpha (7.5-14 Hz), and Beta (14-20 Hz). Increased power of alpha and theta activity in depressed patients at parietal and occipital sites may be caused by decreased cortical activation of these regions. Diffuse enhancement of beta activity level can correlate with anxiety symptoms which take an important place in clinical picture of depressive disorder at early stages. Using of ICA method for comparison of spectral characteristics of EEG in groups of patients with different brain pathology and healthy subjects gives a possibility to localize more precisely the discovered differences as compare to traditional analysis of EEG spectra.     

The Effects of QEEG-Informed Neurofeedback in ADHD: An Open-Label Pilot Study

In ADHD several EEG biomarkers have been described before, with relevance to treatment outcome to stimulant medication. This pilot-study aimed at personalizing neurofeedback treatment to these specific sub-groups to investigate if such an approach leads to improved clinical outcomes. Furthermore, pre- and post-treatment EEG and ERP changes were investigated in a sub-group to study the neurophysiological effects of neurofeedback. Twenty-one patients with ADHD were treated with QEEG-informed neurofeedback and post-treatment effects on inattention (ATT), hyperactivity/impulsivity (HI) and comorbid depressive symptoms were investigated. There was a significant improvement for both ATT, HI and comorbid depressive complaints after QEEG-informed neurofeedback. The effect size for ATT was 1.78 and for HI was 1.22. Furthermore, anterior individual alpha peak frequency (iAPF) demonstrated a strong relation to improvement on comorbid depressive complaints. Pre- and post-treatment effects for the SMR neurofeedback sub-group exhibited increased N200 and P300 amplitudes and decreased SMR EEG power post-treatment. This pilot study is the first study demonstrating that it is possible to select neurofeedback protocols based on individual EEG biomarkers and suggests this results in improved treatment outcome specifically for ATT, however these results should be replicated in further controlled studies. A slow anterior iAPF at baseline predicts poor treatment response on comorbid depressive complaints in line with studies in depression. The effects of SMR neurofeedback resulted in specific ERP and EEG changes.     

EEG spectral power of young schoolchildren with perinatal pathology of the CNS

The influence of perinatal risk factors (prematurity and hypoxia) on the spectral power values of individual EEG frequency bands (θ₁, θ₂, α₁, α₂, β₁, β₂, and γ) in the state of quiet wakefulness in young schoolchildren with educational problems was studied. The results of statistical analysis showed a significant predominance of the power in the θ₁ (especially in the anterior and posterior associative areas), β, and γ (on the whole surface of the cortex, with a predominance of differences in the anterior associative areas) bands in children with a gestational age (GA) less than 38 weeks at birth compared to that in the control group (a GA of 38 weeks). The intergroup differences in the power of most frequency bands were most pronounced in the left temporal area. A relationship between the consequences of perinatal hypoxia and the GA, namely, an increase in the power (especially in the left-hemispheric areas) of all the EEG frequency components (except α₂) in the group with a GA less than 38 weeks, in contrast to its slight inhibition in the control group (except the γ band), was found. The genesis of the specific features of the pattern of local EEG synchronization, as well as their functional significance in the formation of different structures of cognitive disorders in children with perinatal dysontogenesis, is discussed.     

Changes in the EEG power during tests for nonverbal (figurative) creativity

The EEG was recorded in 19 standard derivations according to the international 10–20 system in 30 subjects during a test for figurative creativity. To involve subjects in the creative process, they were presented with the following creative tasks: (Cr1) thinking up and drawing an original picture; (Cr2) drawing a face, a house, and a clown in an original manner; (C1) drawing a picture from memory; and (C2) drawing geometric figures without any system. All the tasks had to be performed using a given set of geometric figures (a circle, semicircle, triangle, and rectangle). Statistical analysis of the EEG spectral power for the frequency bands α₁, α₂, β₁, β₂, and γ showed that the creative task performance was characterized by an increase in the EEG power in the β₂ and γ bands and single differently directed power changes in the α₁, α₂, and β₁ bands. The findings were compared to previous results of EEG studies on creative activity.     

Electroencephalographic Correlates of Brain States during Verbal Learning: I. Characteristics of EEG Local Synchronization

Electroencephalograms (EEGs) were recorded by 19 standard derivations in 57 subjects in a resting state with the eyes opened, during memorization of verbal bilingual semantic pairs (Latin and Russian), and during retrieval (monitoring) of the learned information. Statistical comparison of the EEG spectral power in the frequency bands θ, α₁, α₂, β₁, β₂, and γ showed that induction of the states of memorization (encoding) and retrieval of the verbal information led to multiple significant changes in the EEG absolute power (local synchronization) as compared to the state of rest. Such changes took place simultaneously in different frequency bands over the entire cortex. The relative values and significance of changes in different cortical regions varied. The main features of the EEG power-difference patterns were an increase in the power of the γ band over the entire cortex, a bilateral increase in the power of the β₂ band in the temporal areas, and a decrease in the power of the α₂ and α₁ bands over a large part of the cortical surface. In the state of retrieval, synchronization in the γ- and β₂ bands and desynchronization in the α₂ band were significantly stronger than in the state of encoding. In the α₁ band, desynchronization was more pronounced in the state of encoding than in the state of retrieval. The results are discussed in combination with the available data of the EEG studies of different types of memory.     

Characteristics of the θ and α EEG Bands in 15- to 17-Year-Old Adolescents

A neurophysiological study included 16 males aged 15–17 years and 12 psychologically and neurologically healthy men. The EEG was recorded under conditions of quiet wakefulness (eyes closed), total activation (eyes open), and aversive acoustic stimulation. Under all conditions, the adolescents showed a significantly higher spectral power (SP) in the θ₁ and θ₂ EEG bands and a lower SP in the α₁ and α₂ bands as compared to the adults. Under all conditions and in all frequency bands, the level of interhemispheric coherence (ICOH) between the frontotemporal regions (F_7/8) in the adolescents significantly surpassed that in the adults, whereas, in all other areas, ICOH was lower than in the adults. The opening of the eyes and aversive acoustic stimulation were associated with a decrease in SP in all groups. This decrease was more pronounced in the θ₁ and θ₂ bands in the adolescents compared to the adults and less significant in the α2 band. The EEG was characterized by significant differences in both the initial parameters of the θ and α bands and their activation-induced reactive changes in the adolescents compared to the adults. This finding was explained by brain immaturity in the adolescents of this age group.     

Long-range temporal correlations of broadband EEG oscillations for depressed subjects following different hemispheric cerebral infarction

Abnormal long-range temporal correlation (LRTC) in EEG oscillation has been observed in several brain pathologies and mental disorders. This study examined the relationship between the LRTC of broadband EEG oscillation and depression following cerebral infarction with different hemispheric lesions to provide a novel insight into such depressive disorders. Resting EEGs of 16 channels in 18 depressed (9 left and 9 right lesions) and 21 non-depressed (11 left and 10 right lesions) subjects following cerebral infarction and 19 healthy control subjects were analysed by means of detrended fluctuation analysis, a quantitative measurement of LRTC. The difference among groups and the correlation between the severity of depression and LRTC in EEG oscillation were investigated by statistical analysis. The results showed that LRTC of broadband EEG oscillations in depressive subjects was still preserved but attenuated in right hemispheric lesion subjects especially in left pre-frontal and right inferior frontal and posterior temporal regions. Moreover, an association between the severity of psychiatric symptoms and the attenuation of the LRTC was found in frontal, central and temporal regions for stroke subjects with right lesions. A high discriminating ability of the LRTC in the frontal and central regions to distinguish depressive from non-depressive subjects suggested potential feasibility for LRTC as an assessment indicator for depression following right hemispheric cerebral infarction. Different performance of temporal correlation in depressed subjects following the two hemispheric lesions implied complex association between depression and stroke lesion location.     

Comparison of the effects of the subjective complexity and verbal creativity on EEG spectral power parameters

The EEG recording was made when the subjects performed tasks that involved overcoming the stereotype (creative) and retrieving information from memory (noncreative) with the usual and complicated presentation of the initial material (incomplete proverbs and sayings without concluding words). The subjective complexity of the task performance under different conditions was assessed. The EEG power from 19 EEG derivations was compared in the β₂ and γ frequency bands. The creative task performance was associated with a marked increase in the EEG power; significantly more complicated noncreative tasks were not accompanied by marked changes in the EEG power in these bands.     

Electroencephalograms of patients with initial signs of depression: Independent component analysis

Independent component analysis (ICA) of 19-channel background EEG was performed in 111 patients with the early signs of depressive disorders and in 526 healthy subjects. The power spectra of the independent components were compared in the depressive patients and in healthy subjects at the eyes closed and eyes opened states. Statistically significant differences between the groups were detected in three frequency bands: θ (4–7.5 Hz), α (7.5–14 Hz), and β (14–20 Hz). Increased θ and α activities in parietal and occipital derivations of depressive patients may have been caused by a reduced cortical activity in the projection of these derivation. Diffuse enhancement of the β activity may be correlated with anxiety symptoms that are pronounced in the clinical picture of depressive disorders at early stages of the disease. ICA used to compare quantitative EEG parameters in different groups of patients and in healthy persons makes it possible to localize the differences more accurately than the traditional analysis of EEG spectra.