Reflection of Anxiety in the Characteristics of Evoked EEG Potentials in 10- to 11-Year-Old Children

We studied the peculiarities of the amplitude/time parameters of evoked EEG potentials (EPs) and event-related potentials (ERPs) in 10- to 11-year-old children characterized by low and high anxiety levels. The latter levels were estimated using the scale of the manifest anxiety test of Prikhozhan and projective techniques (“House–Tree–Person,” HTP, and the Lüscher color test). For children with a high anxiety level, the amplitudes of the following EP components and ERPs were lower than those in low-anxiety children of the same age: P1 (predominantly in the occipital region of the left hemisphere), P2 (in the right occipital region), and Р300 wave (in different loci of both hemispheres). In high-anxiety children, we also more frequently observed increased amplitudes of the N2 component in the left parietal and right occipital regions. High-anxiety individuals were characterized by longer latencies of component P1 (mostly in the right frontal and left central regions) and, at the same time, shorter latencies of component N1 (in the parietal and occipital regions of the left hemisphere and also in the right temporal region). Thus, we found that the amplitude/time characteristics of a few EP components and ERPs in children with high anxiety levels differ statistically significantly from the parameters of corresponding EPs/ERPs in individuals of the same age but with low anxiety levels.     

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.     

Hemispheric interaction in man during perception of visual stimuli]

Averaged evoked potentials (AEP) to verbal (letters) and nonverbal (random shapes) stimuli exposed in the left and right visual fields were registered in healthy subjects with normal vision. Analysis of the later AEP latencies pointed to asymmetry in the temporal parameters of the interhemispheric interaction. The late AEP latency is shorter in the right hemisphere than in the left hemisphere. The difference is more pronounced in responses to nonverbal stimuli. The earlier development of the evoked potential in the right hemisphere (or the later one in the left hemisphere) accounts for the interhemispheric difference in the temporal parameters of the late AEP components. Comparison of the latency of the component P300 to verbal and nonverbal stimuli presented in the ipsilateral or the contralateral visual fields reveals a transfer of the results of the cortical processing of visual information in the course of interhemispheric interaction.     

Asymmetry of the transcallosal responses in the parietal cortex of kittens in the 1st month of life

In acute experiments on kittens the process of formation of asymmetry of transcallosal responses (TCR) was studied in multiple leads from symmetrical points of the parietal cortex. By the early positive-negative TCR complex, vanishing as a result of callosotomy, predominance of positive components in the right hemisphere was found in 2-7 days kittens, whereas in 8-24 days animals the left hemisphere dominated by both phases of responses. By the late TCR component preserved after section of the callosal body, left-hemispheric asymmetry was found in the elder group of kittens; it was absent in the younger animals. TCR asymmetry in the parietal cortex depended on the sex of the animals. With their age its inversion and enhancement took place. This process is based on the increase of TCR amplitude in the left hemisphere, with no increase in the right hemisphere.     

EEG characteristics determining the quality of subsequent recognition of visual images

Recognition of noisy pictures of Arabic numerals was accompanied by an increase in EEG coherence in the frontal cortical regions, especially in the left hemisphere, and between the frontal and occipital areas in both left and right hemispheres. Coherence values decreased in the temporo-centro-occipital areas of both hemispheres. A correlation was found between the coherence pattern in the prestimulus period and the quality of subsequent activity. Correct recognition was preceded by left-side asymmetry of the EEG coherence. Before erroneous recognition, EEG coherence levels were higher than before a correct response, and the increase in coherence was widely generalized over the cortex (especially in the Δ, ?, and α₁ frequency bands). The frequency of expression of an increased integral EEG coherence was higher before erroneous recognition than before a correct response. These changes in coherence were symmetrical.     

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.     

Auditory evoked potentials to indifferent and meaningful stimuli in young children

Auditory evoked potentials (AEP) of the frontal, central and parietal cortical areas of the left hemisphere in response to an indifferent sound stimulus and to a stimulus with same physical characteristics, but with acquired informational significance, were studied in healthy children of the 3-d year of life. In the last case the amplitude of the AEPs in all recorded areas rose and the latencies of late components in the parietal area became longer. Moreover, the components of AEP got more complex owing to a greater manifestation of the late positive component P3 in all recorded areas and particularly in the parietal one.     

Characteristics of the perception and imagination of emotions in patients with focal brain pathology

Voluntary components of the emotion perception were shown to be related to the left hemisphere temporal area in patients with focal lesions of postero-frontal and temporal areas of both hemispheres, whereas the involuntary components required involvement of the right hemisphere temporal area. The voluntary components of the emotion reproduction are associated with involvement of the left hemisphere postero-frontal area, whereas involuntary components of perception are related to work of the right hemisphere postero-frontal area. The data obtained suggest that the voluntary (conscious) recognition and reproduction of emotions are mainly related to the sensory and motor speech centres of the left hemisphere, whereas involuntary those involve symmetrical areas of the opposite hemisphere.     

CNV-like potentials on the cortical surface associated with conditioning in head-restrained rats

Head-restrained rats were conditioned to perform a CNV task: to press a lever in response to an imperative auditory stimulus (S2) given 1.5 sec after a warning stimulus (S1) for a drop of jelly food. With an electrode on the surface of the forelimb cortex, (1) sharp wave complexes immediately after S1 and S2, and (2) a negative slow potential (SP) between S1 and S2, on which early and late components were discernible, were recorded in association with performance of this task. With the electrode at a depth of 2 mm in the same cortical area, the corresponding field potential showed a long-lasting positive shift in addition to the components of the surface potential. These monopolar recordings were obtained with respect to a common reference at the frontal sinus. The surface-minus-depth potential (the transcortical potential), consequently, showed a surface-negative tonic wave, confirming Pirch's report (1980). During extinction of this conditioning, the SP between S1 and S2 disappeared, while the sharp waves following S1 and S2 remained with little modification, suggesting that the sharp waves are a kind of evoked potential (EP) elicited by the stimuli.Recording from 5 surface electrodes set in an array over the left hemisphere contralateral to the used forelimb during development of the conditioning revealed not only a spatial distribution of the SP but also a transition of the potentials. As the conditioning progressed, the negativity of the early SP component tended to increase, while that of the late component tended to decrease and was confined to the sensorimotor cortex. The similarities of the rat cortical surface potentials to the human and monkey CNV in their wave form and function suggests that the rat brain can produce electrical activity analogous to the human CNV.     

The functional neuroanatomy of object agnosia: a case study

Cortical reorganization of visual and object representations following neural injury was examined using fMRI and behavioral investigations. We probed the visual responsivity of the ventral visual cortex of an agnosic patient who was impaired at object recognition following a lesion to the right lateral fusiform gyrus. In both hemispheres, retinotopic mapping revealed typical topographic organization and visual activation of early visual cortex. However, visual responses, object-related, and -selective responses were reduced in regions immediately surrounding the lesion in the right hemisphere, and also, surprisingly, in corresponding locations in the structurally intact left hemisphere. In contrast, hV4 of the right hemisphere showed expanded response properties. These findings indicate that the right lateral fusiform gyrus is critically involved in object recognition and that an impairment to this region has widespread consequences for remote parts of cortex. Finally, functional neural plasticity is possible even when a cortical lesion is sustained in adulthood.     

The role of the frontal cortex of the left and right hemispheres in regulating the intraspecific interaction of rats with differing zoosocial experience

By means of the analysis of probabilistic ethological structures of the intraspecies rats behaviour in the test "stranger-resident" and by the method of isolated destruction of the frontal cortex or the left and right hemispheres,--it is established that the frontal cortex of the left hemisphere regulates the intraspecies sociability and keeps it on a certain level, because the change (increase) of the intraspecies sociability is observed only at the unilateral destruction of the left frontal cortex. Isolation from the relatives in early ontogenesis leads to the loss of regulating influence of the left frontal cortex on the intraspecies sociability. In isolated animals the frontal cortex of the left hemisphere regulates the level and probability of the appearance of aggression. The right hemisphere ensures the adequate inclusion of the aggression in the probabilistic ethological structure of the total intraspecies behaviour; at its damage the forms appear of an adequate pathological aggression, and connection is lost between the elements of aggressive behaviour and the acts of intraspecies sociability.     

Electrophysiological Correlates of Vigilance During a Continuous Performance Test in Healthy Adults

The present study evaluated patterns of electrophysiological activity associated with sustained vigilance in healthy adults. Quantitative electroencephalographs (QEEG) were recorded during the performance of a Continuous Performance Test (CPT). Participants were divided into low and high vigilance groups based upon their reaction time changes between the early and late portions of the CPT. Coherence measures were calculated from the QEEG across the baseline, early CPT, and late CPT experimental conditions. Participants in the low vigilance group had higher baseline and CPT frontal to posterior coherence in the alpha and beta bands suggestive of a less vigilant state throughout the entire study. Additionally, the low vigilance group had a significantly greater beta 1 band coherence drop from baseline to the initial portion of the CPT than the high vigilance group. The combined groups had significantly lower amounts of right hemisphere frontal to posterior coherence across a number of frequency bands throughout all of the phases of the study when compared to the homologous left hemisphere sites. These interhemispheric coherence differences are consistent with vigilance network theories that implicate the right frontal and parietal lobes in the maintenance of sustained attention (M. I. Posner & M. E. Raichle, 1994).     

Systemic Organization of Perceptive Activity in Children with Different Levels of Mental Development

Visual evoked potentials (EPs) of the left and right hemispheres in response to relevant and irrelevant stimuli in the structures of the left and right hemispheres have been studied in healthy young schoolchildren, learning-disabled (LD) children, and mentally retarded (MR) children. In healthy children, the largest EP variations depending on the stimulus relevancy have been found in associative structures of the left hemisphere. In LD children of the same age, the amplitude and temporal characteristics of left-hemispheric EPs to target and nontarget stimuli are the same. In MR children, EPs to relevant and irrelevant stimuli do not differ from each other in either the left or the right hemisphere. EP latencies are significantly longer in MR children than in healthy children. The results of simultaneous recording of EPs in the left and right hemispheres during isolated stimulation of the right and left visual half-fields indicate that interhemispheric interaction is impaired in children with deviations in mental development. The results of the study are discussed in terms of the psychological characteristics and learning ability of children.     

Interhemispheric differences in the spatial-frequency description of images and the consequences for visual recognition

Visual perception of images transformed by spatial-frequency filtering was investigated in tachistoscopic experiments. Evidences have been received that the left hemisphere describes preferentially low harmonics of an image, and right hemisphere--the high ones. A hypothesis is suggested that these differences are based on different sizes of the receptive fields of cortical modules. Some consequences of the proposed model are discussed--the consequences for the invariance of visual recognition (innate invariance mechanisms in the left hemisphere and learned invariance in the right hemisphere) and for the methods of visual image classification (discriminant or structural methods in the left and right hemisphere respectively). Some data confirming these predictions are presented.     

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.     

Organization of Regional Interactions of the Brain Cortical Activity during the Common-root Word Derivation Task

This study analyzed specificities in the activity of the neurophysiological mechanisms underlying the organization of active word-derivation processes. The regularities in the reorganization of the spatial structure for the systemic interaction of bioelectrical activity between different cortical areas of the cerebral hemispheres were studied in adult subjects during the test for mental derivation of common root words (i.е., using the modern methods of the so-called “functional connectome” investigations). Сross-correlation and coherent analysis of EEG has shown that the ipsilateral statistical EEG interactions in the left hemisphere, including Broca’s and Wernicke’s areas, were significantly increased in adults during mental derivation of common root words and, simultaneously, the interhemispheric connectivity and the EEG interactions in the right hemisphere were reduced. Comparison of our results with the previous data of verbal activity associated with speech perception and production has revealed significant differences in the degree of involvement of the left and right hemisphere cortical activity in verbal processing. For example, unlike the data of current study, an equal involvement of both hemispheres cortical activity was recorded during the phoneme recognition in auditory perceived words, grammatical and semantic errors in sentences, as well as during mental formation of words from a set of phonemes and sentences from a set of words, which was particularly manifested in the increased of hemispheric interactions, predominantly, in the inferior frontal and temporal areas and the overlapped areas of the temporal, parietal, and occipital cortical zones (TPO) of both hemispheres. Thus, the data obtained in this study indicate the presence of expressed specificities in the lateralization of activity in the neurophysiological mechanisms underlying the processes of active word derivation and inflexion.     

Electrophysiologic analysis of the process of recognizing target and non-target stimuli in healthy and oligophrenic children

In an automatized experiment, with a computer on line, amplitude-temporal parameters of evoked potentials (EPs) to purposive and non-purposive stimuli (digits), were analyzed in normal and mental retarded children. At unilateral stimuli presentation to the left or right visual half-fields EPs were recorded simultaneously in projection, TPO, parietal and central areas of the left and right hemispheres. It has been shown that in normal children, differential involvement of projection and associative structures in the analysis of sensory information takes place in both hemispheres. The amplitudes of most EP components in the range of 100-400 ms to the purposive stimuli are higher than to the non-purposive ones. Considerable similarity of EPs developing in response to ipsi- and contralateral stimulations of visual fields ("direct" and "transmitted" EP) is observed. In mental retarded children significant changes are revealed in intra- and interhemisphere organization of the process of perception of purposive and non-purposive stimuli. In the right hemisphere structures there are no differential EP reactions to the two types of stimuli. Significant, in comparison with the norm, prolongation of the latencies of most EP components is noted, especially in the structures of the left hemisphere, to the purposive stimuli. In the process of perception, changes are seen of the integration of functions of both hemispheres. The totality of disturbances of systemic brain organization at perceptive activity in mental retarded children may reflect neurophysiological mechanisms of mental deficiency.     

Slow Cortical Potentials Preceeding Visually Guided Saccades in Schizophrenics

The parameters of saccades and presaccadic slow potentials were studied in right-handed men with a dominant right eye, including 19 schizophrenics and 12 healthy subjects. For visual stimulation, three light-emitting diodes were used, which were located in the center of the visual field (the central fixation stimulus) and 10° to the right and left of it (peripheral stimuli). Two stimulation protocols were used: with a simultaneous switching off of the central fixation stimulus and switching on of the peripheral stimuli (test 1) and with an interstimulus gap of 200 ms (test 2). According to the latency, saccades were divided into anticipatory, express, and regular. Slow EEG potentials preceding regular saccades were analyzed. It was found that the proportion of anticipatory saccades is considerably higher than the normal value in schizophrenia. The analysis of the presaccadic potentials demonstrated a significant decrease in the amplitude of negative potentials in the vertex region at early stages of presaccadic preparation and its increase in the occipital region at late stages. Test 2 in the patients demonstrated an increase in the positivity focus in the frontal region of the right hemisphere. It was assumed that the alterations found in schizophrenia result from the deficit of frontal cortical fields.     

Changes in emotional face expression recognition caused by an additional visuospatial task

Changes in the recognition of facial expression and spatial synchronization of the cortical electrical activity of the θ- and α-potentials caused by load on working memory were studied in healthy adults by introducing an additional semantic or visuospatial task into the context of experiment with a visual set. An increase in the number of erroneous recognitions of facial stimuli in the form of assimilative illusions was revealed in both types of the additional task. The analysis of the function of coherence of the low-frequency α-potentials indicates (8–10 Hz) a decrease in this situation in the number of connections in the frontal cortical divisions with other cortical zones, which is regarded as a lesser involvement of the frontal system of selective attention in set-forming and set-shifting for an emotionally negative facial expression. Spatial synchronization of the θ-activity (4–7 Hz) with an increase in the load on working memory changes ambiguously in different cortical structures: it decreases in the system of the fronto-temporal connections of the right hemisphere; in the other cortical areas, especially in the left hemisphere, and in the system of interhemispheric connections it substantially increases. The facts confirming the hypothesis that the fronto-thalamic and cortico-hippocampal systems are the two key formations involved in changes in the plasticity of cognitive sets for facial expression are discussed.