V. A. Ponomarev

Comparative efficiencies of different methods for removing blink artifacts in analyzing quantitative electroencephalogram and event-related potentials

Different methods for blink artifact correction in multichannel electoencephalogram (EEG) have been compared with respect to their efficiency and the relative systemic error of the estimation of the parameters of EEG spectra and event-related potentials (ERPs). Three methods of blink artifact correction have been used: distraction of the electrooculogram (EOG) signals from EEG signals, zeroing independent EEG components associated with vertical eye movement, and zeroing the principal EEG components related to blinking. The results have shown that these correction methods can substantially improve the accuracy of the estimation of quantitative EEG parameters while only slightly distorting signals from most EEG sites. It is concluded that wide use of these methods for EEG processing in fundamental and applied studies would be advisable.

EEG-Biocontrol Method in Treating the Attention Deficit Hyperactivity Disorder in Children

The problems of epidemiology, etiology, pathogenesis, and clinical signs of attention deficit hyperactivity disorder (ADHD) in children were considered. The literature review of the EEG-biocontrol method in treating ADHD in children, including the background, the theoretical basis of the method, and the assessment of its effectiveness, is presented. Specific features of the EEG-biocontrol protocols based on the data of different authors are given. The comparative assessment of the efficacy of EEG-biocontrol and drug treatment with the use of psychostimulants in ADHD is presented.

Functional biomarkers in the diagnostics of mental disorders: Cognitive event-related potentials

The article deals with recent research in the field of fundamental knowledge about the mechanisms of information processing in the human brain for the diagnosis of mental disorders performed in the laboratory of neurobiology for action programming of the Bechtereva Institute of the Human Brain of the Russian Academy of Sciences. These studies were connected with the analysis of functional components for cognitive event-related potentials (ERPs) obtained under various behavioral conditions. The main goal of this fundamental approach is the decomposition of multi-channel ERPs into functionally different components. These components are generated in various cortical areas, have different temporal dynamics, and reflect a variety of mental operations. The main methodology we used is the independent component analysis, applied to a large set of ERPs (from hundreds of people) obtained by varying functional conditions in the psychological test. In particular, components related to psychological processes, such as the comparison of sensory signals with a trace in working memory, inhibition of current activity, and monitoring of conflict, were identified in the GO/NOGO test. In the European project, a normative database was constructed for the components described above, and this allowed us to compare the data obtained from large groups of patients (including patients with attention deficit disorder, schizophrenia, obsessive disorders, depression, autism, dyslexia, brain trauma, and dementia) with the healthy subjects. This article presents data from patients with a diagnosis of attention deficit disorder and schizophrenia.

Improving source localization of event-related potentials in the GO/NOGO task by modeling their cross-covariance structure

Nineteen-channel event-related potentials (ERPs) were studied in the GO/NOGO test in 517 healthy subjects. Multi-channel ERPs were decomposed into independent components by the method of modeling the cross-covariance structure of transient process. The research results showed that low-correlated ERP components could be obtained by this method with acceptable reliability. The identified components were associated with psychological processes, such as the attended sensory mismatch operation, decision making on the subsequent action, the action inhibition operation, and the conflict monitoring operation. In conclusion, decomposition of ERP recordings into independent components and the use of sLORETA help to localize ERP sources more accurately than the conventional ERP analysis.

Developmental features of the formation of the brain’s bioelectrical activity in children with remote consequences of a perinatal lesion of the CNS: II. EEG typology in health and mental disorders

The results of studies on the developmental EEG dynamics in children with long-term effects of perinatal CNS pathology are presented. The most common EEG types have been identified, and the differences in their distribution in normal and abnormal mental development were shown. On the basis of the results of a longitudinal study, early markers of the risk of ontogenetic deviations have been described that allow the consequences of perinatal CNS lesion to be minimized and abnormal variants of the formation of higher mental functions to be prevented.

Effect of Biofeedback Training of Sensorimotor and β1EEG Rhythms on Attention Parameters

The effects of the EEG–biofeedback (EEG–BFB) procedure, aimed at increasing the sensorimotor (12–15 Hz) and β(15–18 Hz) rhythms on the psychological and electrophysiological parameters of attention, were studied using the methods of scalp recording of evoked potentials in the bistimulus paradigm Go/No–Go and a psychological attention test (Test of Variables of Attention; TOVA). Twenty-five children with attention disorders were included in the study. EEG–BFB sessions significantly improved the attention, behavior, and school study results in 19 (76%) children. In these cases, a significant increase in the amplitude of the inhibitory component in the frontocentral leads and improvement of the TOVA parameters were found.

Desynchronization and Synchronization of EEG Related to Stimuli Triggering or Forbidding Sensory-Motor Reaction in Adolescents: II. The Peculiarities in Case of the Attention Deficit and Hyperactivity Syndrome

Evoked desynchronization and synchronization of EEG in θ (4–7.5 Hz), α (7.5–14 Hz) and β (14–20 Hz) ranges were recorded by 19 electrodes in healthy volunteer adolescents and those with attention deficit hyperactivity syndrome in the modified GO/NO-GO test. Two stimuli (high and low tone) were presented in pairs with 1 s intervals inside the pair and 1.5 s intervals between the pairs. Test subjects had to push the button in response to presentation of a pair of high tones and to ignore other stimulus combinations. The components of evoked EEG synchronization in α-θ range that were revealed in the frontocentral and temporoparietal brain regions in connection with inhibition of action (inhibition of movements and making a decision to cancel sensory-motor task performance) were statistically significantly lower in subjects with attention deficit hyperactivity disorder compared with that in healthy subjects.

Features of the power spectra of the main EEG rhythms in children with different types of attention deficit hyperactivity disorder

As a result of the examination of a group of 9- to 12-year-old children with the combined type of attention deficit hyperactivity disorder (ADHD), two variants of the clinical picture of ADHD were identified: the residual organic variant (ADHD RO) and the idiopathic variant (ADHD IP). The EEG power spectra in the main frequency ranges were studied with the eyes closed and open. The greatest intergroup differences in the power spectra were observed in the θ-band in the forntocentral and occipital derivations. In the frontocentral divisions of the cortex, the maximal values were observed in the group of ADHD RO children, whereas the highest spectral power values were observed in ADHD IP children in the occipital derivations. No statistically significant differences in the α-band spectral power between healthy subjects and ADHD schoolchildren from either group were obtained. Thus, the studies showed that these two ADHD variants have certain neurophysiological differences, which should be considered when therapeutic modalities are to be selected.

The influence of emotionally significant visual stimuli on cortical evoked potentials

Electrophysiological correlates of the perception of emotional stimuli were studied by means of recording the visual evoked potentials (EP) in 20 derivations (Fz, Cz, Pz, Oz, Fp1/2,F3/4,F7/8,C3/4,P3/4,T3/4,T5/6, andO1/2) during the emotional test performance. The performance of a special task by subjects was assessed positively or negatively (by administering emotionally positive or negative stimuli, respectively). Factor analysis revealed seven factors, which described the EP component structure. Analysis of variance demonstrated the influence of the emotional stimuli sign on the factorsP100,P140,N160,P220,P340, and “slow wave.” Hemispheric difference in reactions to the stimuli of a different emotional sign were recorded. During presentation of the positive and negative assessments, the amplitudes of the factorsP100,P340, and “slow wave” were maximally different in the left hemisphere, while the factorsN160 andP220 were maximally different in the right hemisphere.

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.