Organization of selective attention during preparation for the recognition of global and local characteristics of a visual stimulus in children with different levels of maturity of the regulatory brain systems

Event-related potentials (ERPs) evoked by key stimuli informing a subject about the forthcoming recognition of the global or local level of a hierarchical test figure were analyzed in 7-year-old children with different levels of maturity of the regulatory brain systems. Differences in both the initial ERP components P1, N1, and P2 (which reflect the analysis of the sensory characteristics and significance of a key stimulus) and the late components N3, Pc, and Nc (which reflect the preparation for the recognition of a subsequent test figure) were found. It was shown that, in children with frontal-thalamic regulatory system immaturity (FTRSI), the amplitude of the ERP component N1 is decreased in the caudal areas. In children with an immature bottom-up activation system, a decrease in the amplitude of initial ERP components in the caudal areas was observed in a broader time interval in components P1, N1, and P2. As compared to the control groups of children, in children with immature frontal-thalamic structures, components N3, Pc, and Nc were different in both the caudal and precentral areas. In children with immature lower brainstem activation structures, the late ERP components were different, predominantly, in the parietal and temporo-parieto-occipital areas. Comparison of ERPs in response to global and local key stimuli in children of the control group demonstrated a clear-cut temporal and topographical organization in the period of preparation for subsequent recognition of a prescribed level of the test stimulus: the earlier preparation stages were associated with component N3 in the parietal and temporo-parieto-occipital areas, whereas later stages were associated with Pc changes in the frontal areas. In children with FTRSI, changes in the late components in the caudal areas were poorly expressed and their topographical organization (characteristic of the control group) was absent; the involvement of the frontal areas in the late stages of the key stimulus analysis was restricted. These findings may give grounds to suggest the significance of the frontal-thalamic system in the organization of the response to an expected stimulus. In children with immature lower brainstem activation structures, the type of the key stimulus was reflected in the late ERP components in a diffuse way.     

Recognition of fragmented images and mechanisms of memory

Analysis of the topography and parameters of event-related potentials (ERPs) recorded during the presentation of incomplete images with different fragmentation aided in study of the role of different cortical zones and the order of their involvement in the recognition process. The role of the frontal cortical areas at different stages of perception of fragmented images was established. The differences in the ERPs induced by recognized and unrecognized stimuli in the frontal and frontal-temporal derivations in the interval 30–83 ms were associated with the appearance of early positivity in response to recognized images and development of early negativity in response to unrecognized stimuli. The N300 component associated with recognition was stronger in these cortical zones during identification of images. A late positive complex appeared in the frontal areas earlier than in other areas. Involvement of the caudal visual areas in the recognition process was reflected by enhancement of the components P100, P250, and N400. Our results suggest that the frontal areas play the main role in the recognition of fragmented images because they are the structures that organize extraction of traces from long-term modality-specific memory using a system of afferent and efferent links and determine the strategy of information analysis necessary for the solution of a given task.     

Mechanisms of selective attention in adults and children as reflected by evoked potentials to warning stimuli

Components of evoked potentials to stimuli differing in size and warning about the necessity of subsequent recognition of an image at the global or local level were analyzed to identify the specific features of selective attention in adults and seven-year-old children. In both age groups, components were found that were related to selective attention aimed at processing a warning stimulus (the P1, N1, and P2 components) and producing a response to the subsequent test stimulus. Both age groups exhibited similar dependences of changes in the P1 component (40–110 and 110–220 ms in the adults and children, respectively) on the type of the warning stimulus. The children displayed a greater increase in the amplitude of the P1 component of the response to the global versus the local key than the adults did. The P1 component is suggested to reflect not only the sensory features of the stimulus but also the selective attention associated with its sensory processing. The amplitude of the P2 component of the response to the global key (190–240 and 330–410 ms in the adults and children, respectively) was higher in both age groups. This component is believed to indicate evaluation of the signal importance of the warning stimulus. In the adults, late components of event-related potentials (ERPs), i.e., P3-N3 (300–450 ms), were associated with the global or local level of recognition of a test hierarchical stimulus that was presented after the key, with the greatest differences in the central and posterior associative areas of the right hemisphere and in the frontocentral areas of the left hemisphere. In the children, the N3 component (530–600 ms) in the left parietal area, as well as the late ERP phases, i.e., Ps (680–950 ms) and Ns (1030–1130 ms), during which the frontal cortical areas are involved in preparing the subsequent response, was shown to depend on the type of the warning stimulus.     

Role of the Frontal Cortical Areas in the Analysis of Visual Stimuli at Conscious and Unconscious Levels

Event-related potentials (ERP) in response to complex target stimuli, which consisted of a central recognizable picture and a lateral masked image (analyzed at the unconscious level) were recorded in adult subjects and seven-year-old children. ERP components N200, N300, and P400/N400 had different topography and were differently pronounced in adults and children. In adult subjects, the N200 component that reflects the processing of a sensory stimulus was recorded in the temporo-parieto-occipital and occipital areas. In children, N200 was recorded in the caudal regions and the frontal areas of the cortex. Analysis of different waveforms obtained by subtraction of the ERP to the central stimulus from the ERP to the complex stimulus showed that unconscious stimulus processing in adult subjects is not reflected in the ERP structure. In children, an unconsciously processed image incorporated into a complex stimulus evokes processing negativity in the occipital and frontal cortical areas. Comparison of ERP in groups of children divided by their reflectivity/impulsivity showed that, predominantly, the left frontal area is involved in image analysis at the unconscious level in reflective children and, predominantly, the right frontal area participates in unconscious image analysis in impulsive children. It is suggested that the perfection of the visual recognition of a target stimulus, which contains additional unconsciously processed information, consists in growth of the involvement of the left-hemispheric mechanisms (with respective growth of significance of the left-hemispheric mechanisms) and in a decrease in the role of the frontal areas in analysis of sensory information.     

The Role of Hemispheric Functional Specialization in the Analysis of the Relationship between Signal and Nonsignal Information during Image-Shape Classification

The effect of additional information on image shape classification was studied in seven-year-old children. The classified images were either dissimilar in the axis ratio of the basic oval (F) or had an additional element (F + E). In one series of experiments, the additional element was oriented towards a longer axis of the oval, which was a discriminative sign (situation 1, matching); in another series it was rotated by 90° (situation 2, mismatching). The analysis of the successful image classification in series 1 and 2 showed that images with an additional element that mismatches a discriminative sign were classified as being significantly worse than those with matching information. The analysis of the event-related potentials (ERP) from different cortical areas revealed a specific role of the frontal and temporo-parieto-occipital cortical areas in the classification of additional sensory information. The analysis of additional matching information (series 1) was associated with the right hemisphere and evidenced by an increase in N200 wave amplitude in the frontal area and by a negative shift during the development of a late positive complex (250–550 ms) in the temporo-parieto-occipital area. The analysis of additional information mismatching a discriminative sign (series 2) was associated with the left hemisphere and evidenced by an early positive component (P100) in the frontal area, negative components N200–N250, and a further negative shift during the development of late positive complex in the temporo-parieto-occipital area.     

Event-related potentials at different stages of the operation of visual working memory

Trace fixation and comparison with incoming information was studied using event-related potentials (ERPs) recorded from various cortical areas during passive viewing and matching of two consecutive pictures. Visual stimuli differing in the spatial location of elements (4 × 4 square patterns with random positions of 4 black and 12 white squares) and phonological stimuli (differently written letters) were used. Trace fixation was studied by comparing the ERPs generated in response to the first (reference) stimulus in the pair with those generated during passive viewing. Sensory analysis of the reference stimuli was observed in the time interval 128–196 ms. For the patterns presented, it was reflected by an increased amplitude of the N1 component in the caudal areas as compared with passive viewing. The phonological stimuli produced a higher amplitude of a positive wave in the frontotemporal area in the same time interval. Processing of subsequent information to be stored in memory was observed in the interval 232–452 ms. Processing of patterns was reflected by a decreased positivity, most pronounced in the left temporo-parieto-occipital area. Comparison of a trace with incoming information was studied by comparing the ERPs generated in response to the first (reference) and second (test) stimuli. The number of cortical areas involved in the sensory analysis of the test stimuli was larger than the number involved in the analysis of the reference stimuli. Comparison of the new information with the trace was reflected by an increased amplitude of the late positive wave (components P3, Pc, and Pc-Nc) in the frontocentral and caudal cortical areas. The topographic changes in the late positive components depended on the type of stimulus.     

Brain organization of the recognition of fragmented images in subjects who show different levels of task performance success

We studied the behavioral and EEG changes in healthy adults during recognition of fragmented images presented in a series beginning with a low fragmentation level up to a complete figure. Our sample was divided into two groups according to the recognition success. The first group made few mistakes. The other group made significantly more mistakes compared to the first group; this group had a shorter reaction time and a lower recognition threshold (i.e., the fragmentation level at which the object became recognizable). The ERP analysis showed the statistical dependence between the recognition success and the involvement of the frontal and caudal cortical areas. Compared to the second group, in the first one, we found no significant association between the recognition process and either early or late ERP components in the dorsolateral prefrontal cortex and found an increase of sensory-specific components P1 and P2 in the caudal areas. These results support the hypothesis on the impact of the prefrontal cortex on the successfulness of recognition of fragmented images.     

Development of the brain’s organization of working memory in young schoolchildren

In 7–8 and 9–10-years old children, we studied event-related potentials (ERPs) during paired comparison of non-verbalizable visuospatial stimuli presented at an interval of 1.5–1.8 s. Age-related differences were found in the involvement of various cortical areas in the formation and retention of a short-term memory trace of the reference stimulus and during comparison of the short-term trace with the test stimulus presented. In both age groups, working memory was associated with an elevation of the amplitude of the sensory-specific N1 component in the visual cortical areas. Age-related differences in the processing of sensory-specific characteristics of a stimulus were the greatest in the ERPs to the test stimulus: at the age of 9–10, the N1 component amplitude was significantly increased in all caudal leads and, in the occipital and inferior temporal leads, this component was preceded by P1 component. At this age, we observed the early involvement of the inferior frontal cortex, which was not observed at the age of seven. The increase in positivity over that area was observed in the interval of 100–200 ms. Substantial differences between age groups were found in the late ERP component corresponding to cognitive processes. At the age of 7–8, the presentation of both the reference and test stimuli causes the increase in the amplitude of the slow positive complex (SPC) in the caudal liads with the maximum enhancement found in the interval of 300–800 ms in the parietal leads. At the age of 9–10, the SPC increase, much like in adults, was observed in ERP to the test stimulus only. At this age, adult-like specific changes in the late phases of ERPs were observed in the fronto-central regions at the different stages of working memory. They are the increases in the negative N400 wave in the ERP to the reference stimulus and the SPC to the test stimulus. These data show that, at the age of 9–10, the functional organization of working memory of the adult type is formed; however, the extent to which the frontal cortex, and its dorsal regions in particular, is involved into working memory processes does not meet yet a definitive level.     

Functional Organization of the Brain during the Operation of Working Memory

Event-related potentials (ERPs) recorded from various cortical areas during matching of two consecutive pictures were analyzed. Reflecting the process of trace fixation, the ERP to the reference stimulus was characterized by an increase in components P150 and P300 in the occipital and temporo-parieto-occipital areas and components N300 and N400 in the precentral areas as compared with the ERP elicited by the warning stimulus. The ERP to the test stimulus, which reflected trace retrieval and matching with current information, was characterized by a generalized increase in the late positive complex in the interval 300–600 ms. Similarity and/or dissimilarity of the test and reference stimuli was reflected in the parameters of the ERP to the test stimulus. The results testify to the difference in functional and topographic organization of the brain cortex at the initial and late stages of operation of the working memory.     

Characteristics of event-related potentials in response to symbolical and alphabetical stimulation matrices used in a P300-based brain-computer interface

In order to create a P300-based brain-computer interface (BCI) (the so-called Farwell-Donchin paradigm, FD) with a symbol matrix used as a stimulus, we compared characteristics of event-related potentials (ERPs) in response to stimulation by 6 × 6 matrices composed of either pictogram symbols or Cyrillic alphabet characters. Nine healthy adults were examined in 18 experiments, during which 28-channel EEGs were recorded in the course of stimulation with matrices of these two types. The obtained ERP data, i.e., amplitudes and peak latencies of the ERP components N1, P3 (with the P3a and P3b sub-components), and N4 were compared and analyzed for different types of stimulation matrices. In at least seven out of nine subjects, P3a, P3b, and N4 ERP amplitudes were larger in response to the symbol matrix than to the character matrix, while N1 amplitudes were larger for the character matrix. For N1 and P3a, the ERP latencies were shorter for the symbol matrix, while for P3b and N4, they were longer for the character matrix. The topography of differential ERP responses to the two types of stimuli was analyzed using a series of paired t-tests. Differences of ERP component amplitudes were determined individually for each of the 28 channels; next, for each site, absolute t-test values were summed for all nine subjects. For all ERP components studied, the t-test for peak amplitudes in response to target and non-target letters identified two separate areas with distinct lateralization. ERP responses to target and non-target symbols differed most in transversely extended areas. Finally, the yield surface of differential response to target letters and target symbols had a complex topography.     

Development of working memory brain organization in young schoolchildren

In children of 7-8 and 9-10 years old, the ERP components were studied by comparing two non-verbalized visuo-spatial stimuli shown in succession with 1.5-1.8 s interstimulus interval. We found the age-related differences in the specific way (and the extent to which) the cortical areas were involved into the processes of the reference stimulus (the first stimulus in the pair) encoding and into the process of comparing the memory trace against the test stimulus. In both age groups, the sensory-specific N1 ERP component in the visual cortices had larger amplitude during working memory than during free observation. Age-related differences in the processing of the sensory-specific parameters of a stimulus are most pronounced in ERP to the test stimulus: in children of 9-10, the amplitude of N1 component increased significantly in all caudal leads following the earlier increase in P1 component in the inferior temporal and occipital areas. In the children of that age, unlike children of 7-8, the early involvement of ventro-lateral prefrontal cortex becomes apparent. In that area an increase of positivity confined to 100-200 ms post-stimulus is observed. Substantial inter-group differences are observed in the late ERP components that are related to cognitive operations. In children of 7-8, presenting both reference and test stimuli causes a significant increase in the amplitude of late positive complex (LPC) in caudal leads with maximal increase being observed in parietal areas at 300-800 ms post-stimulus. In children of 9-10, one can see some adult-like features of the late ERP components during different stages of the working memory process: in fronto-central areas N400 component increases in response to the reference stimulus, whereas LPC increases in response to the test stimulus. The data reported in this work show that the almost mature functional organization of working memory is already in place at the age of 9-10. However, the extent of the prefrontal cortex (especially its dorsal areas) involvement does not yet match the level of maturity.     

Analysis of Age-Related Dynamics and Gender-Specific Characteristics of Spontaneous Bioelectrical Activity and Components of Auditory Evoked Potentials in Junior School Students Living in the Arctic Region of the Russian Federation

We studied neurophysiological characteristics of the age-related development in junior school students (7–8 and 10–11 years of age) living in the Arctic region of the Russian Federation. The background electroencephalograms (EEGs) were recorded during quiet wakefulness with the eyes closed and open, and event related potentials (ERP) were recorded during the passive perception of sound stimuli within the oddball paradigm in the group of children (33 subjects, 18 boys and 15 girls). A decrease of the latency period and the spatial rearrangement of mismatch negativity with an increase in the amplitude in the centrofrontal cortex have been revealed in the groups of children aged 10–11 years during the perception of a rare stimulus and a decrease of the latency period of the Р300 component in the central and parietal areas associated with the maturation of mechanisms for involuntary auditory attention. Age-specific differences in the components of auditory ERP (N1 and N2) have been shown during passive perception of rare and frequent sounds, which reflect the processes of the morphofunctional maturation of the brain cortex in healthy Arctic school students (an increase of the N1 component amplitude, a decrese of the amplitude and the latency period of the N2 component). The analysis of the background EEG characteristics has shown both the common features, such as a decrease with age of the EEG power in the Δ and θ bands in the eyes-open state, and the different direction and topographic specificities in the age-dependent reorganization of bioelectrical activity in boys and girls in the α₁ and α₂ EEG bands.     

Temporal and topographic characteristics of evoked potentials in the conflict of two consecutive visual stimuli in a working memory task

Behavioral reactions and brain mechanisms involved in processing two matching or mismatching (conflicting) visual stimuli were studied in healthy subjects (mean age 22.57 ± 0.46 years). Line orientations (vertical, horizontal, or 45°) were used as stimuli and were presented with an interval of 1500–1800 ms. The reaction time was shown to increase in the case of a conflict of two orientations as compared with matching orientations. The reaction time depended on the orientation of the reference stimulus and was minimal when a vertical line was used as a reference. An increase in N2 negativity (time window 200–280 ms) in the frontal and parietal cortical areas was identified as an informative indicator of a conflict between the current orientation and the orientation stored in working memory. The dipole sources of N2 were localized to the prefrontal cortex (middle frontal gyrus, frontal pole, and pars orbitalis). The N2 amplitude was found to depend on the orientation of the first stimulus in a pair, being higher in the case of a 45° orientation. The visual areas were shown to play a role in detecting a conflict of two consecutive signals because the early sensory components increased in amplitude. The results implicate cortical structures, including the sensory-specific visual, parietal, and prefrontal areas, in comparing consecutive visual signals and detecting their conflict.     

Recognition of spatially transformed objects in men and women: Analysis of behavior and evoked potentials

The accuracy, reaction time, and evoked potentials have been analyzed in 16 men and 15 women during recognition of familiar objects at different levels of spatial transformation. Three levels of transformation have been used: in a fixed position relative to each other, all details were shifted in the radial direction (level 1) followed by analogous displacement in combination with the rotation of all details of the figure by ±0?C45 and ±45?C90 degrees (levels 3 and 4). The task performance did not depend on gender: the image transformation resulted in identification impairment, which was the worst in the case of the maximum rotation of the details. The changes in evoked potentials (ERP) are different for men and women. The amplitude of component P1 in the parietal cortex of men is associated with the level of figure transformation: a greater rotation angle leads to a higher response. In women, figure transformation evokes ERP changes in the time window of negativity N150, and they are associated with ungrouping of the figure, but not with rotation of details, and are located in other visual areas: occipital and temporal. The data obtained are discussed in terms of the theory of gender specificity of the visual representation of space.     

Functional organization of working memory in seven- to eight-year-old children

Event-related potentials (ERPs) were analyzed during the operation of working memory (WM) using short-term traces of visuospatial and letter stimuli. A comparison of the two stimuli presented at an interval of about 1500 ms showed differences in the degree and mode of the involvement of the cortical areas during the formation and retention of a short-term memory trace (the first stimulus in the pair) and its comparison with the current information (the second stimulus in the pair). At the stage of trace formation, a significant increase was observed in the amplitudes of the components of the ERPs generated during the analysis and processing of sensory-specific information: visuospatial stimuli caused an increase in the N200 component in the O ₁, O ₂, T ₅, T ₆, P ₃, and P ₄ derivations; and letter stimuli caused an increase in the P200 component in the F ₃, F ₄, F ₇, F ₈, C ₃, C ₄, P ₃, P ₄, T ₃, and T ₄ derivations. The amplitude of the slow positive complex (SPC) significantly increased in the caudal cortical areas, which is not true for adults at this stage of the operation of WM. During a comparison of short-term memory traces with current information, the SPC amplitude significantly increased in the caudal cortical areas in seven- to eight-year-old children; the prefrontal cortex was not involved at this stage of the operation of WM. These findings testify to the insufficient maturity of the central executive of WM at an age of seven to eight years.     

Development of mechanisms of recognition of fragmented images differing in the degree of fragmentation in children of preschool and primary school ages

Recognition of fragmented images with an increasing number of fragments was studied in children of three age groups (five to six, seven to eight, and nine to ten years of age) to compare the behavioral and neurophysiological parameters of recognition in these groups. The most pronounced changes in effectiveness of recognition were observed when the five- to six-year-old and seven- to eight-year-old children were compared. In the former, recognition was not accompanied by any significant changes in the event-related potentials of the prefrontal cortex or by an increase in N250?C400 (Ncl) in the extrastriate cortex (though it is an important characteristic of the process). However, the amplitude of the N170?C200 component, which reflects analysis and encoding of sensory features, did increase at the age of five to six years. Immaturity of the prefrontal cortex is manifested in a deficiency of the control: these children respond hastily and make numerous mistakes. In seven- to eight-year-old children, recognition is accompanied by an increase in the amplitude of the N100 and N250 components in the prefrontal cortex, whereas the amplitude of the Ncl component increases in the extrastriate cortex. The error rate and recognition threshold are significantly lower in these children than at the age of five to six years. The role of prefrontal cortex is the most pronounced at the age of nine to ten years, which is manifested in the Ncl amplitude and the later phases corresponding to the cognitive recognition. Our results demonstrate qualitative differences in the mechanisms of recognition in children of the preschool and primary school age. At the age of five to six years, recognition is a result of integration of the sensory signs. Beginning from the age of seven to eight years, the prefrontal cortex plays an important role in recognition of the fragmentary images; this brain region is responsible for a search of possible analogues in memory and identification of an object.     

Voluntary Modulation of Hemodynamic Responses in Swallowing Related Motor Areas: A Near-Infrared Spectroscopy-Based Neurofeedback Study

In the present study, we show for the first time that motor imagery of swallowing, which is defined as the mental imagination of a specific motor act without overt movements by muscular activity, can be successfully used as mental strategy in a neurofeedback training paradigm. Furthermore, we demonstrate its effects on cortical correlates of swallowing function. Therefore, N = 20 healthy young adults were trained to voluntarily increase their hemodynamic response in swallowing related brain areas as assessed with near-infrared spectroscopy (NIRS). During seven training sessions, participants received either feedback of concentration changes in oxygenated hemoglobin (oxy-Hb group, N = 10) or deoxygenated hemoglobin (deoxy-Hb group, N = 10) over the inferior frontal gyrus (IFG) during motor imagery of swallowing. Before and after the training, we assessed cortical activation patterns during motor execution and imagery of swallowing. The deoxy-Hb group was able to voluntarily increase deoxy-Hb over the IFG during imagery of swallowing. Furthermore, swallowing related cortical activation patterns were more pronounced during motor execution and imagery after the training compared to the pre-test, indicating cortical reorganization due to neurofeedback training. The oxy-Hb group could neither control oxy-Hb during neurofeedback training nor showed any cortical changes. Hence, successful modulation of deoxy-Hb over swallowing related brain areas led to cortical reorganization and might be useful for future treatments of swallowing dysfunction.     

Influence of aggressive computer games on the brain cortex activity level in adolescents

Dynamic changes in the activities of different areas of the brain cortex were studied in order to determine cortical structures responsible for playing aggressive computer games, with the degree of initial aggression of the adolescent subjects taken into account. Changes in anxiety and aggression produced by aggressive computer games were found to depend on the initial level of aggression of the subjects. In adolescents with a high baseline level of aggression, the amplitude of the N200 component increased in the frontal and decreased in the temporal areas of the cortex, whereas, in adolescents with a low baseline aggression level, N200 decreased in the frontal and increased in the temporal cortical areas.     

EEG reactions during creative activity

Evoked activity in response to light was recorded in students performing a verbal creative task. The changes in the amplitude of the N200 negative component of evoked potentials were analyzed. The amplitude of the N200 component was significantly increased in the frontal and anterior frontal areas of the left hemisphere, which indicated increased activity in the cortical structures involved in divergent thinking. The amplitude of the N200 component was increased in the temporo-parieto-occipital area of the right hemisphere, which indicated that the posterior associative region of the right hemisphere was also involved in the creative activity. The data obtained suggest that the frontal and temporo-parieto-occipital areas of the cerebral cortex actively participate in the performance of a creative test with distinct elements of complexity.     

Neurophysiological mechanisms of recognition fragmented images by five- to six-year-old children

Behavioral indices and event-related potentials (ERP) were analyzed in five- to six-year-old children who were shown a set of previously unseen fragmented drawings of familiar images. These children recognized less fragmented images than seven- to eight-year-old children. At the age of five to six years, there was no increase in N350–400 prefrontal negativity and slow positive complex, which is characteristic of mature recognition that involves executive control. Comparison of ERP for recognized vs. unrecognized stimuli revealed a significant increase in the P300 and N400 amplitudes in the right occipital area. Note that, in children of this age, there were no significant differences between reactions to recognized and unrecognized images in the lateral extrastriate cortex (T₅/T₆), which is the key structure for recognition of familiar images via integration of their sensory features. Our data suggest that in five- to six-year-old children recognition of fragmented images has specific features determined by immaturity of the executive control and insufficient involvement of the ventral visual system.