Alpha-band functional connectivity during cued versus implicit modality-specific anticipatory attention: EEG-source coherence analysis.

The anticipation of future events based on a background experience is one of the main components of any goal-directed behavior. Anticipatory attention can be either voluntary (explicit) or involuntary (implicit). We presumed that these two types of anticipatory attention differed in terms of cortical functional organization. We examined this assumption with an experimental model consisting of three experimental sessions (cued attention, implicit learning, and baseline) that were equal in terms of stimuli, motor responses, and cognitive task. Participants were asked to discriminate the temporal order of stimuli within a pair presented in either the visual or auditory sensory modality. Prestimulus functional connectivity was assessed via alpha-band coherence computed in the source space for preselected regions of interests. Functional links between the cortices of the frontoparietal control system increased during the cued attention condition and did not increase during the implicit anticipation condition. The buildup of implicit anticipation was accompanied by the strengthening of functional links between the intraparietal, ventral premotor, and presupplementary motor areas. It was discovered that both cued and implicit types of anticipation were underlain by functional modality-specific cortical links.

[The Influence of Emotional Coloring of Images on Visual Working Memory in Adults and Adolescents].

The influence of emotional valence (positive, negative and neutral) of realistic images on the visual working memory (WM) capacity was studied in adults (N = 40) and adolescents (N = 17). In adults, emotional coloring of stimuli increased the reaction time and decreased the accuracy of WM task performance. This effect was more pronounced for negative than for positive valence: the reaction time has its maximum value for negative emotional stimuli and minimum value for neutral ones with significant differences between all three valences; the accuracy was lower for negative stimuli than for both positive and neutral stimuli. Comparing with adults, adolescents aged 14-16 years showed the lower indices of the performance accuracy and rate during the retention of neutral and positive stimuli in WM. In this group, no significant influence of emotional valence of visual stimuli on the accuracy of WM task performance was found.

[Cortical functional connectivity during retention of affective pictures in working memory: EEG-source theta coherence analysis].

A pattern of cortical functional connectivity in the source space was studied in a group of right-handed adult participants (N = 44:17 women, 27 men, aged M = 29.61 ± 6.45 years) who retained in their working memory (WM) traces of realistic pictures of positive, neutral, and negative emotional valence while in their working memory (WM) while performing same different task in which participants had to compare an etalon picture against a target picture that followed after a specified delay. A coherence (COH) between pairs of cortical sources chosen in advance according to fMRI data was estimated in the theta frequency range for the period of time preceding the etalon stimulus, distinct sets of functional links are found. The links of the first type that presumably reflect the involvement of sustained attention were between the dorsal anterior cingulate cortex, the prefrontal areas, and temporal areas of the right hemispheres. When compared to the rest period, links of this type showed strengthening not only during the retention period but also during the period preceding the etalon picture. The links of the second type presumably reflecting a progressive neocortex-to-hippocampus functional integration with increasing memory load and strengthened exclusively during retention period. Those links were between parietal, temporal and prefrontal cortices in the lateral surface of both hemispheres with the additional inclusion of the posterior cingulate cortex and the medial parietal cortex in the left hemisphere. An impact of emotional valence onto the strength and topography of the functional links of the second type was found. In the left hemisphere, an increase in the strength of cortical interaction was more pronounced for pictures of positive valence than for pictures of either neutral or negative valences. When compared to the pictures of neutral valence, the retention of pictorial information of both positive and negative valence showed some extraneous integration of the cortical areas for the theta rhythm. This finding might be related to the additional load exerted by emotionally colored pictures onto the mechanisms of short-time retention of visual information.

[Event-Related Potentials Accompanying Processing Referentially Ambiguous Pronouns in Russian].

The study is based on the analysis of event-related potentials (ERPs) accompanying processing referentially ambiguous pronouns under condition when disambiguation is necessary for effective task performance. Par- ticipants were asked to match the pronoun in the second sentence with its antecedent (the noun phrase it is related to) in the first sentence in two conditions: experimental (two possible antecedents) and control (only one possible antecedent). Processing referentially ambiguous pronouns as compared to the control condition elicited an Nref effect - a diffuse ERP deflection 300-400 ms poststimulus that was earlier observed in Dutch and Chinese. Moreover, in contrast to previous results, no P600 effect - late positivity associated with ac- ceptability judgment under condition of referential ambiguity - was found. Our data in comparison with re- sults of previous studies indicate that strategies in processing referentially ambiguous pronouns (acceptability judgment) are determined not only by experimental task but also by absence/presence of anomalous trials in the experimental materials.

[Assessing Regulatory Components of the Cognitive Performance in Children Aged 5-10 with EEG Patterns of the Limbic System Non-Optimal Functioning].

This study represents the results of interdisciplinary (EEG and neuropsychological) examination of the limbic system non-optimal functioning influence on the cognitive activity regulation in 5-6, 7-8, 9-10-year- old children. Neuropsychological measures of cognitive activity regulation were compared between groups: children with EEG patterns of the limbic structures nonoptimal functioning (group 1); children without deviated EEG patterns (group 2); children with EEG patterns of the fronto-thalamic system nonoptimal func-. tioning (group 3). It was shown that children with EEG patterns of the limbic system non-optimal functioning, regardless of their age, demonstrate emotional and motivational deficits comparing with two other groups and, first of all, poor emotional and motivational regulation. Seven-to-eight-year-old children of experimental group have severe difficulties in understanding and recognizing other people's emotions and intentions. Children aged 5-6 of the same group were the only who demonstrated deficit of different executive functions. Children at the age 5-8 had low energy to fully complete the task, poor concentration and slow cognitive processing speed. However, those manifestations considered to be nonspecific for the poor limbic functioning and expand to the cases with the fronto-thalamic non-optimal functioning.

[The Influence of the Functioning of Brain Regulatory Systems onto the Voluntary Regulation of Cognitive Performance in Children. Report 2. Neuropsychological and Electrophysiological Assessment of Brain Regulatory Functions in Children Aged 10-12 with Learning Difficulties].

A total number of 172 children aged 10-12 were electrophysiologically and neuropsychologically assessed in order to analyze the influence of the functioning of brain regulatory systems onto the voluntary regulation of cognitive performance during the preteen years. EEG patterns associated with the nonoptimal functioning of brain regulatory systems, particularly fronto-thalamic, limbic and fronto-striatal structures were significantly more often observed in children with learning and behavioral difficulties, as compared to the control group. Neuropsychological assessment showed that the nonoptimal functioning of different brain regulatory systems specifically affect the voluntary regulation of cognitive performance. Children with EEG patterns of fronto-thalamic nonoptimal functioning demonstrated poor voluntary regulation such as impulsiveness and difficulties in continuing the same algorithms. Children with EEG patterns of limbic nonoptimal functioning showed a less pronounced executive dysfunction manifested only in poor switching between program units within a task. Children with EEG patterns of fronto-striatal nonoptimal functioning struggled with such executive dysfunctions as motor and tactile perseverations and emotional-motivational deviations such as poor motivation and communicative skills.

[The Influence of the Functional State of Brain Regulatory Structures on the Programming, Selective Regulation and Control of Cognitive Activity in Children. Report I: Neuropsychological and EEG Analysis of Age-Related Changes in Brain Regulatory Functions in Children Aged 9-12 Years].

Age-related changes in brain regulatory functions in children aged from 9 to 12 years with typical development were studied by means of neuropsychological and EEG analysis. The participants of the study were 107 children without learning difficulties and behavior deviations; they were devided into three groups (9-10, 10-11 and 11-12 years). The neuropsychological tests revealed nonlinear age-related changes in different executive brain functions. The group of 10-11-year-old children showed better results in programming, in- hibition of impulsive reactions and in the perception of socially relevant information than the group of 9-10- year-old children. At the same time, these children had more difficulties with selective activity regulation as compared with the younger group. The difficulties were mainly caused by switching from one element of the program to another and by retention of learned sequence of actions. These children also showed a lower level of motivation for task performance. The children aged 11-12 years had less difficulties with selective activity regulation; however, impulsive behavior was more frequent; these children also had a higher level of task performance motivation than in children aged 10-11 years. The analysis of resting state EEG revealed age-related differences in deviated EEG patterns associated with non-optimal functioning of fronto-thalamic system and hypothalamic structures. The incidence of these two types of EEG patterns was significantly higher in children aged 10-11 years as compared with children aged 9-10 years. The EEG of the groups of 10-11 and 11-12-years-old children did not show any significant differences.

[The brain executive systems].

The analysis of neuromorphological, neurophysiological, neurocognitive and neuropsychological data demonstrates the specific involvement of lateral, medial, orbital and rostral parts of prefrontal cortex in the selective regulation and organization of goal-directed behavior. Functional specialization of different prefrontal areas depends on their co-operation with posterior associative cortices and subcortical brain structures such as the mediodorsal thalamic nucleus, hippocampus, amygdale and basal ganglia. Separate cortical and subcortical structures are included in functional networks which provide different aspects of the brain executive functions.

[Cortical Functional Connectivity during Cued vs. Implicit Modality-Specific Anticipatory Attention: EEG-Source Alpha Coherence Analysis].

The brain functional organization was studied in a group of healthy right-handed adults (N= 16, mean age = 23 ± 5.7) during preparation for visual and auditory sensory tasks in two conditions: (1) participants waited for appearance of either a visual or an auditory stimulus after being cued about its sensory modality (the cued anticipatory attention) or (2) they developed implicit anticipation of stimulus in the course of repetitive exposure to the same sequence of visual and auditory stimuli pairs. In both cases, participants were asked to discriminate the temporal order of stimuli presentation within a pair of either visual or auditory modality. The functional connectivity was assessed via alpha coherence computed in the source space for preselected regions of interests. For both visual and auditory modalities, increase of strength of functional links among cortical areas involved in the fronto-parietal attention system is found during the cued attention when compared to nonspecific sustained attention. An increase is also observed in the connection strengths between sensory-specific and associative (parietal and prefrontal) areas. In visual modality, the buildup of implicit anticipation was accompanied by the strengthening of functional links between the ventral premotor cortex and caudal (parietal and occipital) areas of the right hemisphere. In the case of auditory task, the increase of connection strengths within fronto-temporal cortical areas was observed. These areas included the rostral supplementary motor areas, ventral premotor cortices and primary auditory cortices.

[Interdisciplinary approach to analysis of brain mechanisms of learning difficulties: application to the ADHD children study].

The study presents the interdisciplinary approach to the analysis of the brain mechanisms of learning difficulties in primary schoolchildren. The neuropsychological assessment and the resting-state EEG estimation were applied to analyze the neurophysiological factors of cognitive deficits in children with ADHD symptoms aged 7-8 and 9-10. EEG recordings of children with ADHD symptoms more frequently, as compared to children with typical development, contained EEG patterns of the fronto-thalamic system non-optimal functioning, reflected in frontal theta waves (FTW), right hemisphere local electrical activity (EA) deviations and EEG patterns associated with the general activation deficit arising from the brainstem reticular formation (DA). We specified cognitive impairments associated with different types of resting-state EEG deviations in ADHD children. Children with FTW of both age groups demonstrated pronounced difficulties in programming, regulation and control (executive functions) and verbal performance. Children with right hemisphere local EA abnormalities had executive functions deficit combined with difficulties in nonverbal performance. Children with EEG signs of DA of both age groups had a decreased cognitive processing speed and efficiency. Younger children with DA demonstrated difficulties in nonverbal task performance. Thus, the interdisciplinary study provided the evidence for at least three neurophysiological factors which can specifically impede the cognitive performance in ADHD children.

Spatial organization of cortical electrical activity at different stages of a visual set in preschool and early school age.

Parameters of the formation of a visual nonverbal set and the rate of its replacement with a new set were compared in children of three age groups: 5-6, 6-7, and 9-10 years. The vast majority of subjects (27 of 30 preschool children and 42 of 43 third-grade children) showed clear set effects. Age-related differences in set plasticity and the dynamics of reaction times to test stimuli were observed. The set was more rigid in children aged 5-6 years than in older children. Differences in the dynamics of the spatial organization of alpha and theta activity were seen in the anterior areas of the cortex at different stages of the set in children of different age groups. Analysis of cortical potentials coherence functions and behavioral parameters led to the hypothesis that the frontothalamic selective attention system and the corticohippocampal connection system responsible for the cortical processing of new visual information and episodic memory function are involved in organizing the visual set. A critical age (from six to seven years) was identified in the formation of plastic types of visual nonverbal sets.

The effects of lesions to subcortical conducting pathways on the electrical activity of the human cerebral cortex.

Simultaneous assessment, during the neurorehabilitation process, of electroencephalographic and neurological data, along with computerized tomography and computerized emission tomography data from patients suffering from sequelae due to ischemic insult allowed the organic origin of a number of EEG phenomena to be identified. These studies showed that lesions to the conducting pathways between the cortex and subcortical structures due to circulatory pathology in the territory of the middle cerebral artery were accompanied by local changes in the electrical activity of the cortex, mainly in the form of polymorphic waves in the theta and delta frequency ranges, along with groups of theta oscillations. The nature of slow-wave oscillations depended on the extent of the lesions and the severity of the blood supply loss in the affected area. Reductions in the size of the lesion focus and improvements in blood supply during rehabilitation were accompanied by changes in the nature of local abnormalities in cortical electrical activity: polymorphic slow-wave activity was replaced by sharp waves in the alpha and theta frequency ranges. Localization of changes in the caudal part of the cortex was an unfavorable prognostic factor for patients with ischemic insult, in terms of recovery of motor function.

Dynamic character and age dependence of functional brain organization in attention.

Intrahemispheric functional organization was studied during a task expectancy period with special reference to attention mechanisms. The estimation of coherence of functionally identical rhythmic EEG components was made to characterize the intracortical integration. Several factors influencing the possibility to make an adequate prognosis and to realize it were varied. Different types of the task (objective factor) were used. Subjects of different ages (7, 9-10 years, young adults) and children of the same age differing by the brain maturity level (subjective factor) were studied. It was shown that all factors studied have a certain influence on the brain organization underlying the task preceding attention. Clear age differences as well as the lag between the possibility to formation and realization of the prognosis in children were observed. Alternative "strategies" used in different ages to facilitate the task performance were analyzed; the underlying mechanisms were discussed.