Yu. D. Kropotov

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.

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.

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.

Study of local EEG specificities in children with mental development disorders using independent component analysis

Baseline EEGs in the frequency range of 3–13 Hz in children with mental disorders of perinatal origin during wakefulness with the eyes open were analyzed using independent component analysis. In cases of severe mental retardation, a significant increase in the power density spectra of the θ band was revealed in the left-sided frontotemporal and right-sided temporal cortices, which allows us to consider these regions to be putative sources of slow activity and markers for a lesion or immaturity in the fronto-thalamic system, as well as for the temporal areas responsible for the auditory analysis and synthesis of speech signals and the integration of audio-visual information.

Brain structural and functional characteristics in children with mental disorders and the possibilities of transcranial direct current stimulation

Analysis of the magnetic resonance imaging (MRI) data in children with mental disorders of perinatal origin showed that, in 70% of cases, pathological damage to the brain structures is absent, or only minimal residual changes are detected. At the same time, the EEG α-rhythm in the occipitoparietal areas was not regular in 77% of cases. The predominance of the signs of cerebral functional insufficiency allows efficacious use of the physiological methods of correction of mental disorders using transcranial direct current stimulation.

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 possibility of using biofeedback for training the amplitude of independent components of event-related potentials

The possibility of voluntary training of the independent component of event-related potentials (ERPs) by the method of biological feedback (BFB) using a modified two-stimulus test of Go/NoGo paradigm was studied. Ten subjects had to increase the amplitude of the P3b component of ERPs induced by the Go stimulus during one training session. This component is generated in the parietal cortex and is associated with an operation of action engagement. The study consisted of three sessions that included determination of the average amplitude, training, and placebo. It was found that the amplitude of the P3b component did not significantly change during the training and placebo sessions as compared to the session of threshold measurement, whereas the amplitude of the SPD component, which was also observed in ERPs in response to the Go stimulus, significantly decreased in both sessions. According to the sLORETA data, the source of the SPD component is located in the parahippocampal area. The results obtained help to determine further pathways to study the possibility of the use of BFB for correction of components of cognitive evoked potentials.

Comparison of Methods for Clustering Independent EEG Components in Healthy Subjects and Patients with Postconcussion Syndrome after Traumatic Brain Injury

The efficiencies of three clustering methods for independent components of 19-channel baseline EEG in location of pathological cerebral activity sources were compared. The samples comprised 518 healthy subjects and 87 patients with postconcussion syndrome after traumatic brain injury (TBI). Clustering of independent component topographies, the spatial coordinates of equivalent dipole sources corresponding to independent component topographies, and locations of the maximums of the equivalent source current density calculated by standardized low resolution electromagnetic tomography (sLORETA) were compared. A comparison of the power spectra of independent components showed a significant increase in the EEG power in the Δ, θ, and α bands for sources located in the frontal and temporal lobes of TBI patients compared to healthy subjects. The method of clustering of independent component topographies proved to be the most sensitive of the methods compared.