Spectral power of θ and α-EEG bands in preschool children with different levels of visual set plasticity

The spectral powers (SPs) of the θ and α EEG rhythms were studied at different stages of visual set in children from five to seven years of age. Children with a plastic set had a greater α band SP than those with a rigid set. At the set formation stage, children with a rigid set displayed an increase in the SP of the θ band, which is a manifestation of an “immature” activation reaction. Children with a plastic set exhibited an increase in the α band SP in the occipital lobes of both hemispheres. The dynamics of the SP of the EEG rhythms differed in children younger and older than six years. At the set formation stage, children from five to six years of age exhibited the above-mentioned “immature” activation reaction, while those from six to seven years of age showed an increase in the α band SP in the occipital lobes. At the set actualization stage, an increase in the α band SP was observed in the right caudal areas, while the set extinction stage was marked by a bilateral depression of the α band in the frontal lobes. The importance of the involvement of specific cortical areas in visual perception and the formation of a plastic set is discussed.     

Visual nonverbal set in preschool- and schoolchildren

Visual set for perception of unequal circles was formed in 5-6-year-old preschool- (n = 30) and schoolchildren (n = 43). Children of 5.3-6.1 years old formed a less rigid set than 9-10-year-olds. The reaction time to a probe stimulus significantly depended on the set stability and stage. The role of structural maturation of the frontal cortical areas in set formation and stability is discussed. The factor of set rigidity was shown to be significant for cognitive activity.     

Spatial synchronization of cortical electrical activity at different stages of visual set in preschool children

Changes in the alpha-rhythm synchronization were revealed at different stages of cognitive visual set in 5- to 7-year-old children. We found a clear-cut correlation of these changes with set plasticity. In children with a plastic set, the EEG synchronization between the frontal and other brain regions substantially increased in the period of set-shifting (the actualization stage). At the set extinction stage, after set-shifting has already taken place, the EEG-synchronization becomes minimal. On the contrary, in children who formed a rigid set, EEG coherence considerably increases at the set extinction stage. This finding suggests that the rigid set still affects the cognitive activity even after (judging from oral reports) the set shift has been completed. The age-related differences in cognitive set formation clearly correlate with the time course of the EEG synchronization between the frontal and other brain regions. We think that the ability to form a plastic visual set depends on the frontal cortex maturation, which occurs at the age of 6-7 years, and its age-related effect on the brain cognitive functions.     

Prestimulus EEG gamma frequencies during formation of a cognitive set to facial expression

Prestimulus EEG power spectra from different cortical areas in frequency band 1-60 Hz were studied at a stage of formation of the cognitive set to facial expression. Diversity of individual power spectra of baseline EEGs, especially in gamma frequency band 41-60 Hz makes averaging individual spectra impossible. The authors pioneered in finding that, in prestimulus periods, EEG frequencies 41-60 Hz were of higher information value than frequencies 1-20 and 21-40 Hz. The highest power of the gamma frequencies was revealed in the frontal areas of the right hemisphere in subjects with a plastic set. In the group with a rigid set, gamma frequencies of high power prevailed in the posterotemporal and occipital areas of the left hemisphere.     

Baseline gamma activity EEG and induced responses to facial stimuli of the visual cognitive set

Power spectra of cortical potentials of baseline activity during interstimuli intervals (4 s; Fourier transform in the frequency band of 1-60 Hz) and short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15-60 Hz band) were assessed in the study of the visual cognitive set to facial expression. Significant differences between groups of subjects with different set rigidity were observed only at the set-testing stage. Estimation of the short-term (0.8 s) induced responses of the wavelet spectra in the group with plastic set revealed an increase in the power (in comparison with the power of background activity) of the gamma2 band (41-60 Hz) in the left hemisphere of the temporal, central and occipital areas, whereas in the group with rigid set these power spectra decreased. At the same time the power in the gamma1 band (21-40 Hz) was significantly lower (at the same level with the rigid form), indicating a discrete nature and functional selectivity in the gamma frequency band.     

Dynamics of the gamma-band power of induced EEG responses to facial stimuli with increased visual working memory load

The dynamics of power of short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15-60 Hz band) were assessed in the study of the visual cognitive set under conditions of different loads on working memory in two groups of subjects. Subjects of the first group had to react only to facial stimuli (n = 29), whereas the second group solved an additional task loading the working memory (they had to find a target stimulus in a matrix of letters, n = 35). We estimated wavelet spectra in the occipital, temporal, central and frontal areas of both hemispheres. In both groups of subjects with the plastic form of set, the power level in the gamma2 band (41-60 Hz) was significantly higher than in subject with the rigid form. In group A at the set-testing stage, the largest increase in the gamma2 band was related to the central areas of the left hemisphere. In more complex situation (group ), the increase in power in the gamma2 and gamma1 (21-40 Hz) bands was observed in the occipital and temporal areas of both hemispheres. At the same time, the EEG power of the central areas in these gamma bands was significantly lower. In the frontal areas there were no significant differences in the dynamics of power between the subjects of both groups.     

Induced cortical electrical activity during different time-spans between warning and target stimuli

A certain alpha-band EEG dynamics was revealed in healthy adults (n = 16) at the interval between a warning and a target stimulus in a simple visuospatial task (subjects were instructed to locate a specific letter in the table of letters). Two series of experiment--either with a 2-sec or a 9-sec inter-stimulus interval were conducted, each consisting of 60 trials. In both series, we observed an induced desynchronization of low alpha (8-10 Hz) at the first second after the warning stimulus and its desynchronization just before the target stimulus. In series with a 9-sec inter-stimulus interval at the 4-6 s of it we observed an alpha-band synchronization, especially distinct in high alpha (10.5-13 Hz). This synchronization gradually reduced towards the end of the inter-stimulus interval. We consider the above changes in alpha-band spectral power during the inter-stimulus interval to be induced by "inner impulsations" caused by an internal representation (set) of the stimuli time-sequence. Changes in the level of cognitive control during the inter-stimulus interval cause increases and decreases in fronto-thalamic system activity, which are manifested in changes of alpha-band spectral power. Analysis of theta-band dynamics suggests that cortico-hippocampal system doesn't participate in this process.     

Integrating role of voluntary postural control recovery during rehabilitation of patients with traumatic brain injury

Results of complex clinical, stabilographic and electroencephalographic (EEG) examination of 20 patients (28 +/- 6.9 years) suffered a severe traumatic brain injury (STBI) are presented. The examination was carried out in early terms after the STBI before and after a course of stabilographic training (ST) with a visual feedback as compared to a group of 18 healthy volunteers (26 +/- 5.8 years). The 4- to 6-week course of ST consisted of 8-15 sessions. Before the course, the patients experienced problems in different kinds of activity, maximum in the motor sphere. The EEG study revealed a decrease in the power and coherence of the alpha rhythm and an increase in the power of the slow spectral bands (delta). The ST restored not only the postural control of patients, but also reduced the defects in other spheres. The EEG study showed an increase in the alpha-rhythm power maximum in the occipital-parietal areas and a tendency to normalization of its regional specificity. In all examined patients, the interhemispheric coherence increased for different EEG-rhythms, especially of the alpha-band, in the central and parietal brain areas. The described EEG changes can be a marker of the integrating role of postural control and an important stage in restoration of integrative brain activity in early terms after the STBI accompanied by improvement of damaged functions.     

Spectral analysis of the human EEG while listening to music

EEG was recorded from 16 electrodes (International 10-20 System) in 14 healthy volunteers aged from 18 to 45 in the state of rest and during listening to music (popular classical symphonic pieces). The EEG spectral analysis was carried out. Presentation of musical pieces increased the EEG spectral power in the alpha-range in the parietal and occipital areas of both hemispheres. During repeated listening of the same musical fragment there was a tendency for attenuation of these changes. A significant decrease in the peak frequency of the alpha-band was found in the process of listening. The spectral values did not significantly differ between the left and right hemispheres. The findings suggest a decrease in the level of CNS activation under the influence of music.     

Spectral characteristics of EEG during formation a set to illusory length perception (Müller-Lyer illusion)

A cognitive set to illusory perception of linear relationships was formed in 56 young healthy subjects. After 10 presentations of Müller-Lyer figures, 39 subjects formed the stable set. In 17 subjects the unstable set was formed. The spectral power of the EEG led from different cortical areas was studied at different stages of set formation. Analysis of variance showed that the factors "set stage" and "group" x "set stage" x "hemisphere" exert significant influence on the EEG spectral power in the delta range in the frontal area. In the subjects with stable set, the power of this spectral component increased at the stages of set formation and actualization and returned to its initial values during set extinction. The between-group difference was more expressed in the left hemisphere. In subjects, which formed the stable set, the power of the occipitotemporal alpha rhythm in the reference state was higher than in subjects with the unstable set. In the process of set formation, the dynamics of the alpha spectral component (8-10 Hz) was more expressed in the stable group: its power increased to a greater extent at the stages of set actualization and extinction. In both groups, there were no significant changes in the alpha2 power over the course of the experiment.     

Alterations of spectral parameters of rat brain electrical activity after sciatic nerve section

Changes in electrophysiological brain characteristics accompanying the development of neurogenic pain syndrome induced by transsection of sciatic nerve were analyzed. At the maximum pain syndrome 3 weeks after the deafferentation, a reorganization of the brain electrical activity was observed in the limbic structures (hippocampus, amygdale, and nucleus accumbens), frontal cortex, and the caudate putamen. An increase in the relative spectral power of the delta and alpha bands and a decrease in the relative power of the beta2 band (as compared to baseline activity) took place. Alteration of the electrical activity in the limbic structures did not depend on manifestations of the neurogenic pain syndrome (autotomy). The increase in the relative spectral power of the alpha-band activity in all the structures under study suggests the involvement of the reticular thalamic nucleus in pathogenesis of neurogenic pain syndrome.     

The age-related features of influence biofeedback training on efficiency of functional state voluntary regulation in young schoolchildren

The aim of the study was to assess an impact of biofeedback training (5 sessions) onto the voluntary regulation of the brain functional state (relaxation) in two groups of children of 7-8 and 9-10 years old. EEG alpha-band spectral coherence and skin resistance were measured during pre-relaxation, relaxation and post-relaxation phases before and after training. Short-term memory test was used to evaluate behavioral changes in functional state regulation before and after training. The group of children of 9-10 y.o. was the only group that showed any significant relaxation-related changes of spectral coherence in alpha-band after training. Besides, that group showed a significant post-relaxation improvement in short-term memory volume. We found a number of individual psychophysiological indices that influenced an efficiency of the biofeedback training.     

Baseline EEG gamma activity and induced responses to facial stimuli during the formation of a visual cognitive set

The power spectra of cortical potentials of baseline activity during interstimulus intervals (4 s; Fourier transform in the frequency band of 1–60 Hz) and short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15–60 Hz band) were assessed during the study of the visual cognitive set to facial expression. Significant differences between groups of subjects with different set plasticities were observed only at the set-testing stage. Estimation of short-term (0.8 s) induced responses of wavelet spectra in the group with the plastic set revealed an increase in the power (compared to the power of background activity) of the γ₂ band (41–60 Hz) in the temporal, central and occipital areas of the left hemisphere, whereas in the group with the rigid set these power spectra decreased. At the same time, the power in the γ₁ band (21–40 Hz) was significantly lower (at the same level with the rigid form), indicating the discrete nature and functional selectivity in the γ frequency band.     

Spectral EEG characteristics in students with different anxiety profile during tests

EEG spectral power was calculated in 39 students at the age of 19-21 years in two experimental conditions: during the common educational process and immediately before an examination (stress condition). During the education process, in subjects with high anxiety (tested by Spielberger) the relative spectral power of the delta activity was higher than in the other group in the occipital, parietal, central, and right frontal brain areas, whereas the power of the EEG alpha in these areas was lower. Before examination tests, in subjects with high activity the delta power bilaterally increased in the temporal areas, whereas in subjects with low anxiety there was a decrease in the alpha rhythm power, especially in the right frontal area. In stress condition, the relative power of the delta activity in both occipital and temporal, right parietal and central areas was higher in subjects with low anxiety, whereas their alpha power was lower in both frontal and in occipital, parietal, and temporal areas of the left hemisphere.     

Features of the spectral power of the EEG rhythms in autistic children and their relation with the progress of different symptoms in schizophrenia

Right hemispheric dominance of the baseline alpha-band spectral power was revealed in 5-7 years boys with autism. This feature persisted during performance of a cognitive task (counting). Also, boys with autism showed lowered level of the alpha spectral power as compared with healthy children. In healthy children, the gamma spectral power increased during performance of the cognitive task as compared to baseline state. Autistic persons showed higher values of the gamma spectral power as compared with normal boys. Boys with autism showed less expressed changes in the gamma spectral power during the cognitive task than healthy children. The reduced spectral power of the alpha band in autistic boys may serve as a precursor of conversion from autism to schizophrenia. Higher level of the gamma spectral power in autistic boys is characteristic also of schizophrenic patients with positive symptoms. Lowered levels of fast rhythms reactivity revealed in autistic boys and the same effect earlier described in schizophrenic adults probably have the similar nature.     

Theta and alpha-band EEG spatial synchronization under the conditions of visual set, formed to an angry face expression. A study of 5-11-year-old children

EEG coherence in theta and alpha bands during set-forming and set-shifting was studied in 5-6-year-old (n=18) and 10-11-year-old (n=25) children. Set was formed to visual stimuli (facial photos with emotionally negative expression). Younger children displayed smaller coherence values, especially in the right hemisphere, than older ones. We also revealed differences in theta and alpha band coherence in cases of a rigid and a plastic set. For example, EEG-coherence values were smaller when cognitive processes were relatively rigid (i.e., in a case of a slower set-shifting). A strong correlation between electrophysiological and behavioral data supports the hypothesis that cortico-hippocampal and fronto-thalamic brain integration systems participate in facial expression recognition and provide cognition flexibility.     

EEG Correlates of Emotional Problems and Conduct Disorder in Schoolchildren

The relationships between EEG and the teachers' and parents' ratings of conduct disorder and emotional problems were studied in 20 schoolchildren between the ages of 9 to 13 years. For the assessment of behavioral and emotional problems, we used the Rutter questionnaire for teachers and the Achenbach questionnaire for parents. The intelligence was determined with the Wechsler test. The electroencephalogram was recorded at rest with eyes open and closed, from 16 derivations, using the international 10–20 system. Correlation analysis, controlling the effects of age and sex, and stepwise multiple regression analysis revealed a positive relationship between the ₁ relative spectral power and parental ratings of delinquent behavior and teachers' ratings of hyperactivity and conduct disorder. The relative spectral power of the band positively correlated with the intelligence and negatively, with the teachers' ratings of conduct disorder and hyperactivity. Children with high parental ratings of anxiety and depression and low teachers' ratings of hyperactivity had higher spectral power of the band in the left occipital region than in the right region. The average difference between the spectral power of the band in the derivations P ₃ and P ₄ with eyes open and closed correlated negatively with the parents' ratings of attention deficit. The discussion of the results involves the relationship between impulsiveness and arousal and the role of the right hemisphere in the generation of emotions.     

Brain Correlates of Non-Symbolic Numerosity Estimation in Low and High Mathematical Ability Children

Previous studies have implicated several brain areas as subserving numerical approximation. Most studies have examined brain correlates of adult numerical approximation and have not considered individual differences in mathematical ability. The present study examined non-symbolic numerical approximation in two groups of 10-year-olds: Children with low and high mathematical ability. The aims of this study were to investigate the brain mechanisms associated with approximate numerosity in children and to assess whether individual differences in mathematical ability are associated with differential brain correlates during the approximation task. The results suggest that, similarly to adults, multiple and distributed brain areas are involved in approximation in children. Despite equal behavioral performance, there were differences in the brain activation patterns between low and high mathematical ability groups during the approximation task. This suggests that individual differences in mathematical ability are reflected in differential brain response during approximation.     

EEG correlates of individual differences in performance efficiency of students during examination stress

Performance of cognitive tests and EEG spectral power were evaluated in 39 students aged from 19-21 years in two conditions: during common educational process and immediately before examination (stress condition). Before examination, the performance was better in subjects with low level of spectral density in the delta band (in the occipital, parietal, central and frontal cortical areas) and high level of the alpha-rhythm spectral density in all the cortical areas, A decrease in performance scores before examination was correlated with an increase in the delta activity (in the right frontal and temporal cortical areas) and rise of the anxiety level (tested by Spielberger).     

Electrophysiological characteristics of cardiac function and the intensity of protein synthesis in cardiomyocytes during the arousal of susliks from hibernation

It has been demonstrated that during winter hibernation (body temperature 2-4 degrees C), the heart rate in ground squirrels is equal to 100 10-12 beats/min. At the initial stage of the arousal, while body temperature remains still low (9-10 degrees C), the heart rate may increase up to 160-200 beats/min. At this stage, practically all electrophysiological parameters of the heart correspond to those in active animals. These results may indicate the ability of "cold" heart in arousing ground squirrels to operate as a normothermic organ and reveal certain role of the heart in body warming. Significant increase of the intensity of protein synthesis in cardiomyocytes together with periodic changes in protein composition of their membranes were found during arousal which may account for regulation of the level of metabolism in cells and for adaptation of the latter to different temperatures.