Mechanisms of Classification of Visual Objects in Children with Different Styles of Cognitive Activity

A sample of seven-year-old children was divided into reflective and impulsive groups using the matching familiar figures test (MFFT). Event-related potentials of different regions of the cerebral cortex were studied in children from these groups performing classification of visual-object shapes on the basis of only one discriminative feature or with the use of additional information. Comparison of the success of visual-stimulus identification in reflective and impulsive children under the conditions of alternative choice (MFFT) and classification according to a specified discriminative feature demonstrates differences in the mechanisms of both selection and analysis of the sensory characters of the stimulus. When the shape of a visual object is classified according to the discriminative feature, the initial stages of analysis in impulsive children are accompanied by the emergence of wave N80 in the left hemisphere, which may reflect the higher rate of detection of the discriminative feature by these children. Impulsive children are also characterized by an earlier development and a higher amplitude of component P300 compared to reflective children. In the latter, waves N250 and N350, indicating continuing information processing, are superposed on this positive component. If the picture presented to children contains an element consistent with the discriminative feature, the N350 amplitude in the right temporo-parieto-occipital region and the negative shift corresponding to the N350 wave in the left temporo-parieto-occipital region are increased in reflective and impulsive children, respectively. Additional information increased wave N400 in the left frontal region.     

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.     

Developmental changes in the mechanisms of image classification in young schoolchildren with different cognitive styles

Testing of 7- to 8- and 9- to 10-year-old children with the matching familiar figures test revealed groups of children differing in the time and accuracy of the reaction of choice from several alternatives. Classification of simple images and images with additional information congruous with the main discriminative character improved with age in children without evident signs of reflectivity or impulsivity (the main group) and in reflective children. No significant improvement was revealed in impulsive children. Developmental changes in the event-related potentials during image classification differed in character and location in children with different styles of cognitive activity. In the children of the main group and in the reflective children, the developmental changes consisted of an increase in the amplitude of the late positive complex predominantly in the caudal areas of both brain hemispheres. In the impulsive children, in the age period from 7–8 to 9–10 years, the late negative component N350 became more distinct, especially in the left hemisphere, and substantial reorganization of the involvement of the frontal areas in the classification process took place. The opposite electrophysiological changes in children with different cognitive styles testify to different developmental changes in the mechanisms of visual recognition.Translated from Fiziologiya Cheloveka, Vol. 31, No. 1, 2005, pp. 15–23.Original Russian Text Copyright © 2005 by Beteleva, Petrenko.     

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.     

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.     

Functional specialization of hemispheres in matching current and preceding stimuli

Classification of visual patterns, a differentiating sign of which is the position of the longer axis of an oval and the principal part of the image, was studied. Stimuli were presented at random to the left (LVF) or right (RVF) visual fields in two situations:same (preceding imageS ₁ was of the same form and presented to the same visual field as the current imageS ₂) anddifferent (S ₁ differed fromS ₂ by both form and location). Classification ofdifferent images was less effective compared with that ofsame images during stimulation of LVF and showed no dependence on the preceding image during stimulation of RVF. The matching of event-related potentials (ERP) in response toS ₂ and differential curvesS ₂−S ₁ revealed the processes related to accessing the information on the preceding stimulus and processing of the current stimulus, which simultaneously occur during the initial 50 ms in both hemispheres and in the 160–180 ms interval in the right hemisphere. Both processes were more expressed during stimulation of the contralateral visual field. In the 190–310 ms interval, discrimination of thesame anddifferent images was determined by processing of information about the current stimulus on the basis of the results of the preceding stage of analysis. This process was more expressed in the occipital, parietal and temporoparietooccipital regions of the right hemisphere independently of the stimulated visual field. The involvement of frontal regions at this stage of information processing was observed only at stimulation of RVF. The dependence of differences of ERP to thesame anddifferent images on the stimulated visual field was revealed for the 320–500-ms interval (N ₄₀₀ and late positive complex) in the occipital regions.     

A study of staining for electron microscopy using collagen as a model system—VIII. Simulation of the negative staining pattern

Simulated negative staining patterns of collagen fibrils were prepared for visual display by a graphical procedure in which amino acid side-chains along the staggered molecules were weighted according to their stain-excluding capacity. The simulated patterns were then compared directly with electron-optical images of collagen fibrils negatively stained with sodium phosphotungstate or lithium tungstate. These visual comparisons confirm previous observations that satisfactory matching occurs when side-chains are weighted according to their ‘bulkiness’ (average cross-sectional area or ‘plumpness’). Optimal matching at the edges of the overlap zones occurred when a hairpin-like conformation was assumed for the N-terminal telopeptides and a condensed conformation for the hydrophobic part of the C-terminal telopeptides. The negative staining pattern is known to include some element of positive staining; visual matching suggests that this additional uptake of positive staining ions occurs predominantly in the more accessible gap zone in a fibril D-period. A slight mismatching between observed and simulated patterns can be understood if the gap zone suffers greater axial shrinkage than the overlap zone when specimens are prepared for electron microscopy.     

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.     

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.     

Negative Potentials of the Human Brain Elicited in Saccadic Latency during Stimulation of the Leading and Nonleading Eyes with an Overlap

Fast presaccadic EEG potentials in saccadic latency were studied with the use of inverse averaging during monocular stimulation of the leading or nonleading eye. Two paradigms were followed, with presentation of visual stimuli consecutively or with a 200-ms overlap. Irrespective of the paradigm and the stimulated eye, the negative N ^–1 potential in the interval of 50–20 ms preceding the beginning of the saccade predominated in the hemisphere contralateral to the saccade direction, reflecting the command processes of saccadic initiation. The N ^–2 potential was more pronounced in the case of direct averaging, starting from the stimulus. Its amplitude increased with increasing concentration of attention on the fixation stimulus under the overlap conditions, and its foci predominated in the left hemisphere, in the frontal, central, and parietosagittal regions. Hence, the N ^–2 potential was assumed to reflect spatial perception and attention as initial stages of saccadic programming. The findings testify to the priority of the leading eye both in fixation and in spatial attention.     

The music of your emotions: neural substrates involved in detection of emotional correspondence between auditory and visual music actions

In humans, emotions from music serve important communicative roles. Despite a growing interest in the neural basis of music perception, action and emotion, the majority of previous studies in this area have focused on the auditory aspects of music performances. Here we investigate how the brain processes the emotions elicited by audiovisual music performances. We used event-related functional magnetic resonance imaging, and in Experiment 1 we defined the areas responding to audiovisual (musician's movements with music), visual (musician's movements only), and auditory emotional (music only) displays. Subsequently a region of interest analysis was performed to examine if any of the areas detected in Experiment 1 showed greater activation for emotionally mismatching performances (combining the musician's movements with mismatching emotional sound) than for emotionally matching music performances (combining the musician's movements with matching emotional sound) as presented in Experiment 2 to the same participants. The insula and the left thalamus were found to respond consistently to visual, auditory and audiovisual emotional information and to have increased activation for emotionally mismatching displays in comparison with emotionally matching displays. In contrast, the right thalamus was found to respond to audiovisual emotional displays and to have similar activation for emotionally matching and mismatching displays. These results suggest that the insula and left thalamus have an active role in detecting emotional correspondence between auditory and visual information during music performances, whereas the right thalamus has a different role.     

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.     

Activation in a frontoparietal cortical network underlies individual differences in the performance of an embedded figures task

The Embedded Figures Test (EFT) requires observers to search for a simple geometric shape hidden inside a more complex figure. Surprisingly, performance in the EFT is negatively correlated with susceptibility to illusions of spatial orientation, such as the Roelofs effect. Using fMRI, we previously demonstrated that regions in parietal cortex are involved in the contextual processing associated with the Roelofs task. In the present study, we found that similar parietal regions (superior parietal cortex and precuneus) were more active during the EFT than during a simple matching task. Importantly, these parietal activations overlapped with regions found to be involved during contextual processing in the Roelofs illusion. Additional parietal and frontal areas, in the right hemisphere, showed strong correlations between brain activity and behavioral performance during the search task. We propose that the posterior parietal regions are necessary for processing contextual information across many different, but related visuospatial tasks, with additional parietal and frontal regions serving to coordinate this processing in participants proficient in the task.     

Structural rearrangements of the cerebral cortex in children and adolescents

The cortical formations of the brain involved in visual functions (the occipital and temporo-parieto- occipital areas, the oculomotor area of the prefrontal cortex), as well as the motor cortex in the representation zone of the arm and the medial region of the frontal cortex adjacent to the limbic lobe, were studied in post-mortem material. The thickness of the cortex and cortical layer III, the sizes of pyramidal neurons, the specific volumes of neurons and intracortical vessels were studied in subjects of both sexes, from birth to the age of 20 years, at yearly intervals (103 observations) using histological techniques, computer morphometric and stereological analysis. The thickness of the cortex of the cerebral hemispheres was observed to intensively increase from birth to the age of 3 years in the occipital, temporo-parieto-occipital and prefrontal cortical areas involved in visual recognition processes. The increase in thickness of the cerebral cortex continues until the age of 6 in the occipital cortex and in the oculomotor area, until the age of 7 years in the temporo-parietooccipital area and the medial prefrontal area, and until the age of 8–9 years in the motor cortex. The sizes of pyramidal neurons increase until the age of 6 years in the motor cortex, until the age of 8 years on the medial surface of the frontal lobe, and until the age of 9–10 years in the temporo-parieto-occipital area and in the dorsolateral area of the prefrontal cortex. The specific volume of neurons and blood vessels in the cortex of the cerebral hemispheres decreases and the volume of intracortical fibers increases throughout the ascending ontogeny, which is manifested most intensively in the prefrontal cortex.     

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.     

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, Fp _1/2,F _3/4,F _7/8,C _3/4,P _3/4,T _3/4,T _5/6, andO _1/2) 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 factorsP ₁₀₀,P ₁₄₀,N ₁₆₀,P ₂₂₀,P ₃₄₀, 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 factorsP ₁₀₀,P ₃₄₀, and “slow wave” were maximally different in the left hemisphere, while the factorsN ₁₆₀ andP ₂₂₀ were maximally different in the right hemisphere.     

Structural Transformations of the Associative Cortex As the Morphological Base of the Development of Human Cognitive Functions from Birth to 20 Years of Age

The microstructure of the temporo-parieto-occipital subregion and the frontal area of the brain from birth to 20 years of age was studied using computer morphometry. These brain zones are involved in the higher integrative mechanisms of cognitive functioning in children, adolescents and young adults. Structural transformations of the cortex represent a stage-by-stage process. Each stage in the frontal and occipital associative zones has specific temporal limits and is characterized by the quantitative and qualitative specificity of the morphological changes at each of the system levels considered: neuronal, modular, and stratification. The structural modifications from birth to early adulthood are primarily associated with the final development of micro and macroassembles and their structural components, primarily, neurons of various types. The growth and differentiation of neurons involves heterochrony with respect to the terms and developmental rates in the frontal and occipital associative cortex. The terms of the most active synchronous postnatal structural modifications, occurring during the first year of life, during the years 2–3, 6–7, 9–10, and 13–14 were analyzed. It was shown, that local specialization of cellular ensembles at various levels is a consequence of the functional specialization of microensembles, involved in cortical information processing, including cognitive activity and other higher psychophysiological functions of the human brain.     

Early and late patterns of stimulus-related activity in auditory cortex of trained animals

 Epidural electrocorticograms over the right auditory cortex (field AI) were measured using implanted 18-channel (3×6) electrode arrays in four animals (Mongolian gerbil) trained to discriminate between a rising and a falling frequency modulated tone (frequency range 2–4 kHz). Using a previously introduced classification procedure, transient patterns of cortical activity suitable to discriminate between the rising and the falling modulation were identified. Early (locked to stimulus onset) and late (emerging at variable times poststimulus) patterns could be differentiated. Deletion of increasing numbers of randomly selected electrodes was used to determine a critical density of recording channels required to capture the discriminative power of the early and late patterns. Statistical analysis of the classification revealed a sigmoid dependence of the discriminative power from the number of remaining electrodes with an inflection point at 12 electrodes. The analysis of the minima of the classification statistic revealed that in the early patterns discriminative information was focal on regions corresponding to the tonotopic representation of the stimuli, whereas in late patterns this information seemed to be distributed nonfocally across larger cortical regions. This analysis supports the previous notion of the coexistence of topographically organized activity states related to the physical stimulus features and nontopographically organized states determined largely by intrinsic factors (Ohl et al. 2001). Received: 25 January 2002 / Accepted: 26 November 2002 / Published online: 11 April 2003 Correspondence to: F. W. Ohl (e-mail: frank.ohl@ifn-magdeburg.de, Tel.: +49-0391-6263322, Fax: +49-0391-6263328) Acknowledgements. Supported by grants from BMBF and Land Sachsen-Anhalt. We thank M. Dobrowolny, E. Müller, and K. Ohl for their skilled technical support in various parts of the work.     

Functional brain organization of global and local visual perception: Analysis of event-related potentials

Event-related potentials (ERP) of the brain and psychometric indices (reaction time and percentage of correct responses) were studied in adult subjects during recognizing hierarchical visual stimuli (letters), while the subject’s attention was drawn to either the global or the local level of the stimulus. The psychophysical indices demonstrated the global precedence effect, i.e., an increased recognition time of a small letter, which was a part of an incongruent stimulus. The ERP component analysis demonstrated that differences in the regulatory mechanisms of attention and timing and topography of brain organization during processing of visual information depended on the level of recognizing the hierarchical stimulus (global vs. local). Visual recognition at the local level was accompanied by a stronger activation of visual associative areas (P _z and T ₆) at the stage of sensory feature analysis (P1 ERP component), as well as by the predominant involvement of the temporal inferior cortex of the right hemisphere (T ₆) at the stage of sensory categorization (the P2 ERP component) and of the frontal cortex of the right hemisphere at the stage of selection for the relevant target features (the N2 ERP component). Visual recognition at the global level was accompanied by significant involvement of the early sensory selection (the N1 ERP component) and predominant activation of the parietal cortex of the right hemisphere (P ₄) at the stage of sensory categorization (the P2 ERP component), as well as at the stage of identification of the target stimulus (the P3 ERP component). Perception of a stimulus at the global level is assumed to depend mostly on the analysis of its spatial features in the dorsal visual system, whereas perception at the local level involves analysis of the object-related features in the ventral visual system.