Post-radiation effect on the interhemispheric asymmetry in EEG and thermography characteristics

Complex analysis of EEG and thermographic parameters carried out in 10 healthy subjects and 34 patients, Chernobyl clean-up participants revealed a correlation between EEG and brain temperature changes in the baseline state and during mental arithmetic. During cognitive activity the maximal increase in the average EEG coherence and temperature shifts in healthy subjects were observed in the left frontotemporal and right parietotemporal areas. In patients changes in both parameters under study were most pronounced, the interhemispheric relations were impaired. The visual analysis revealed "flat" and "hypersynchronous" EEG types in patients. The dominant pathologic activity in the betal range indicative of mediobasal and oral brainstem lesions was characteristic of the flat EEG. This type of activity was observed in 60% of patients. In these cases, a general decrease in EEG coherence and temperature was most pronounced in the left hemisphere. The hypersynchronou EEG type (40% patients) was characterized by paroxysmal activity in the theta and alpha ranges suggesting diencephalic brain lesions. In these cases, EEG coherence and temperature were more variable; changes in the right hemisphere were significant, be it increase or decrease. Our complex approach to investigation of brain activity in different aspects seems to be promising in estimation of the brain functional state both in healthy persons and patients in remote terms after exposure to radiation. The specific hemispheric temperature changes revealed in Chernobyl patients especially during cognitive activity can be the sequels of postradiation disorders of vascular neuro-circulation. The EEG findings suggest subcortical disorders at different levels (diencephalic or brainstem) and functional failure of the right or left hemispheres in remote terms after exposure to radiation.     

Age-related specificity of the frontal and temporoparietal cortex activation levels in three-to seven-year-old children

The results of studies on the specificity of formation of the frontal and temporoparietal cortex activation levels in children aged three, four to five, and six to seven years with a normal development of higher mental functions and speech are summarized. The parameters of the stable millivolt-range potential recorded from the head surface were used for this purpose. The results obtained are compared with published data on the specificity of the morphological and functional organization of the brain and the level of development of the slow information control system estimated on the basis of EEG parameters at the same ages. The estimation of the contribution of the brain superslow information control system by one of the basic parameters of state makes it possible to determine, in quantitative terms, (1) the characteristics of the formation of activation levels of cerebral systems involved in the regulation of the resting state, higher mental functions, and speech at different stages of ontogeny; (2) (on the basis of the stable-potential variance) the degrees of freedom of the activation levels of the cerebral systems studied, which determine their regulatory capacity at different ages; and (3) the degree of development of the system-forming mechanisms combining all these systems into an integrated whole at a certain stage of ontogeny (from six to seven years of age).     

Dextrals and sinistrals (right-handers and left-handers): specificity of interhemispheric brain asymmetry and EEG coherence parameters

Data of literature about morphological, functional and biochemical specificity of the brain interhemispheric asymmetry of healthy right-handers and left-handers and about peculiarity of dynamics of cerebral pathology in patients with different individual asymmetry profiles are presented at the present article. Results of our investigation by using coherence parameters of electroencephalogram (EEG) in healthy right-handers and left-handers in state of rest, during functional tests and sleeping and in patients with different forms of the brain organic damage were analyzed too. EEG coherence analysis revealed the reciprocal changing of alpha-beta and theta-delta spectral bands in right-handers whilein left-handers synchronous changing of all EEG spectral bands were observed. Data about regional-frequent specificity of EEG coherence, peculiarity of EEG asymmetry in right-handers and left-handers, aslo about specificity of EEG spectral band genesis and point of view about a role of the brain regulator systems in forming of interhemispheric asymmetry in different functional states allowed to propose the conception about principle of interhermispheric brain asymmetry formation in left-handers and left-handers. Following this conception in dextrals elements of concurrent (summary-reciprocal) cooperation are predominant at the character of interhemispheric and cortical-subcortical interaction while in sinistrals a principle of concordance (supplementary) is preferable. These peculiarities the brain organization determine, from the first side, the quicker revovery of functions damaged after cranio-cerebral trauma in left-handers in comparison right-handers and from the other side - they determine the forming of the more expressed pathology in the remote terms after exposure the low dose of radiation.     

Spatial organization of EEG in rats with genetically determined emotionality

In order to study the possibility of EEG discrimination of genetically determined emotionality (increased propensity to emotional and stress reactions and anxiety) brain electrical activity was recorded in rats of two strains: Maudsley Reactive and Maudsley Nonreactive (24 derivations from the convexital skull surface were used). The program package "Synchro-EEG" was used for EEG processing. It was demonstrated that the two rat strains were significantly different in 120 EEG parameters of 840 ones analyzed. On the basis of 37 parameters, each rat was correctly recognized as belonging to the respective group with the error of 4.89%. The analysis of the detected signs allowed their classification to be performed in accordance with the peculiarities of the emotional and cognitive processes and the level of nonspecific activation. Specific forms of interaction between these components in the system of emotional reactions were revealed.     

The age-related characteristics of the organization of brain electrical activity in 7- to 14-year-old schoolchildren with neuroses in different functional states

By the method of factor analysis characteristics of functional brain states in children and juveniles of different age with neuroses were studied by EEG data. Similarity was established of the patients EEG structure at strained and emotional states. In the studied period of individual development (7-14 years) the most expressed changes of background EEG were observed at the age og 9-12 years. At functional loads, beginning from the age of 9-10, insufficient activity of the frontal region of the left hemisphere was found. The greatest changes of the EEG integral characteristics were observed in patients with vegetative-emotional disturbances and the smallest-at verbal-motor ones.     

The reflection of different levels of the regulation of human brain activity in spectrally coherent EEG parameters]

On the basis of clinico-anatomo-electroencephalographic studies it was shown, that in early terms of cerebral trauma, at gross disturbances of the cortical functions and safety in some cases of only vital regulation, the parameters of the EEG stability or variability are of distinct information value for estimation of the functional state of patients. It was established, that changes of stability of the frequency, power, and coherent EEG characteristics correlate with different parameters of changes of the structural-functional brain organization. At this stage the greatest connection with the disease outcome reveals the EEG coherence parameters of the cortical symmetrical points reflecting the state of predominantly median formations and general brain reactions to traumatic action. In the process of restoration of disturbed neuromental functions priority prognostic significance is acquired by parameters of intrahemispheric coherence as well as by frequency-regional properties of interhemispheric asymmetry of coherence of the brain electrical processes, characterizing functional features of the lesion focus.     

Functional interrelation of the brain structures of the cat during the generation of rhythmic activity. I. The frequency characteristics of the electroencephalogram

The similarity of frequency parameters of electroencephalograms (EEG) recorded from visual, associative and sensorimotor cortical area, caudate nucleus and several thalamic nuclei have been analysed using the period analysis of EEG and cluster analysis of data obtained to clarify the functional interrelationships between these parts of the brain during generation of rhythmic activity of different types. Functional interrelationships between brain structures in freely moving cats during the states of drowsiness and slow-wave sleep have been shown to differ from "classical" thalamo-cortical pacemaker relations.     

Development of psychomotor tempó (tapping speed and stability) and EEG alpha frequency in 7 to 15-years-old children

The psychomotor tempo (tapping) and its relation to alpha frequency was investigated in 100 7- to 15-year-old children. The frequency of alpha rhythm increased in proportion to age, and the maximum and preferential tapping frequencies revealed an increasing tendency, too. Mainly the preferential tapping frequency correlated with the age-dependent increment of EEG alpha frequency. Simultaneously, the variability of the tapping frequency decreased. During a phase of relatively stable tapping performance regular fluctuations in the tapping frequency occurred with a period duration between 0.67 and 13.3 s. These oscillations of the motor activity developed during ontogenesis: The slow fluctuations were found in all groups, whereas those with shorter periods were best pronounced in the older children. The development of EEG and psychomotor indices are assumed to be based on the morphological and functional maturation of the developing brain. Therefore, they may be used as a tool to assess the normal and disturbed brain development.     

Cortical-subcortical interactions and the brain functional state regulation under acute hypoxia in man

Regulation mechanisms of the brain functional state (FS) were studied in man during acute hypoxic conditions (inhalation of 8% O2 hypoxic air for 15-25 minutes). Changes in balance of the brain regulatory structures activities caused by hypoxia determine FS dynamics that is reflected in the reorganization of the EEG spatial interrelations (by data of factor and cluster analysis of EEG cross-correlation matrices), as well as translocation of intracerebral position of electrical equivalent dipole sources (EEDS) coupled with EEDS density rising in medial and basal regions of the cerebral hemisphere temporal lobes (by EEDS-tomography data). Alterations of the cortical-sub-cortical interactions show a decline in the brain activating system tone, a decrease in the neocortical inhibitory control of subcortical processes, and activation of structures of limbic and hypothalamic regions. Switching of integrative regulatory control mechanism from "cortical-thalamic" system level to "limbic-dyencephalic" one could ensure both removal of powerful unspecific components of hypoxic stress and a greater stability of essential physiological parameters of the main vital functions regulation during oxygen deficiency accumulation.     

Comparison of reactive EEG changes and fMRI characteristics of brain health based on multivariate statistics

To gain a deeper insight into the relationship between the electrogenesis and oxygenation of the brain, fMRI and EEG reactions to identical functional loads (opening of the eyes and right- and left-hand fingering) were compared in 11 young right-handed healthy subjects with statistical techniques. Changes in power, frequency and coherent EEG parameters obtained by 18-channel monopolar recording were compared with values of + BOLD-fMRI response, calculated for 18 corresponding cortical areas on the basis of application of the "virtual cap" by the original algorithm. In reactive changes of both hemodynamic and bioelectrical parameters, sets of independent factors were identified, which were regarded on the basis of their topography as specific (localized in the cortical representation ofa relevant analyzer) and nonspecific (diffuse and similar under different functional loads). Specific component dominated in the fMRI response, whereas non-specific component was characteristic of the EEG reaction. The similar topography of reactive fMRI and EEG factors under normal conditions, confirmed by the correlation analysis, reflects the multilevel character of the systemic organization of the brain activity, visualized, in particular, in the sagittal projections of the individual fMRI images. Each of the reactive EEG factors included all of the EEG quantitative characteristics. EEG coherence, which dominated among other parameters (with a local increase in the cortical representation of a relevant analyzer and a diffuse decrease in the areas of the influence of the regulatory structures) displayed the highest correlation with hemodynamic responses of the brain.     

Electroencephalographic markers of the spontaneous recovery of the vertical posture in patients with consequences of traumatic brain injury

Nine patients (mean age, 23.6 ± 3.15 years) with a severe traumatic brain injury (TBI) associated with a loss of the ability to maintain vertical posture were enrolled in a comprehensive clinical and electroencephalographic study during the spontaneous recovery of vertical posture (VP). The patients were divided into three groups according to their functional deficit assessed on the international MPAI, FIM, and MMSE scales, which was determined by the severity of the TBI. The EEG data were compared to those of ten healthy subjects (mean age, 22.8 ± 0.67 years). In patients with a moderate impairment of the brain and a rapid recovery of VP (over two weeks), a change in the sitting position revealed EEG signs similar to reactive EEG restructurings of healthy individuals during the maintenance of VP in the form of a predominant EEG coherence increase in the right hemisphere for most of the rhythm bands; however, at this stage of VP recovery, the EEG restructurings retained pathological signs. In patients with a more severe functional deficit, spontaneous recovery of VP was accompanied by hyperreactive EEG restructurings for all rhythm bands without regional specificity. This finding showed up irrespective of the lateralization of the brain injury, which could be considered as a marker of positive dynamics of VP recovery. In patients with the most severe impairment and functional deficit and long-term (more than three months) absence of spontaneous VP recovery, the absence of reactive EEG restructurings was revealed in their passive verticalization, which could be used as a marker of negative prognosis.     

Study of the genesis of pathological EEG patterns in tumor and traumatic lesions of the human brain

Computer-assisted superimposition of the equivalent dipole sources (EDSs) of the main pathological EEG patterns with the results of computer tomography and magnetic resonance imaging of the brain was performed for patients with organic CNS lesions. The greatest degree of structural determination was revealed for local and lateralized (in a traumatic injury) slow waves, whose EDSs mapped to the perifocal zone of the injury focus. The EDSs of epileptiform patterns could be located in the zone of damaged brain substance or in the intact hemisphere (when the limbic structures were damaged), reflecting the formation of secondary functional foci in the latter case. Bilateral paroxysmal patterns were more frequently determined by the functional state of the medial brain structures. The EDSs of pathological (diencephalic, hippocampal) activity were closely associated with the corresponding anatomical brain structures, although without a strict dependence on the degree of their morphological intactness.Translated from Fiziologiya Cheloveka, Vol. 31, No. 1, 2005, pp. 24–32.Original Russian Text Copyright © 2005 by Boldyreva, Sharova, Koptelov, Shchepetkov, Nikitin, Kornienko, Fadeeva.     

Dynamics of the Adolescent EEG Parameters with Changes in the CNS Functional State (Relaxation) Influenced by Rhythmic Acoustic Stimulation

Age-related specific features of the regulation of the CNS functional state (relaxation) were studied in adolescents between the ages of 14 and 15 years using 6-Hz rhythmic stimulation. The dynamics of the EEG findings (spectral power density, coherence functions) in the quiet wakefulness–relaxation–initial-state cycle was analyzed. The dynamics of the functional state was controlled by changes in the electrodermal resistance (EDR). The data showed that the studied group of adolescents was heterogeneous by the effectiveness of self-regulation: the majority was characterized by marked shifts whose distribution character was close to normal; the others, by mild EDR changes. It was shown that, with the use of rhythmic stimulation, relaxation shifts were more marked than those induced by common psychotherapeutic techniques. The basic relaxation changes in the EEG parameters are related to changes in the coherence function values, i.e., increases in its values, especially those of distant relations (with the focus) of significant connections in the frontal regions. The rate of the occurrence of relaxation changes in the coherence values is substantially higher in the low-frequency band (5 to 7 Hz) than in the EEG -band, constituting 20 to 50% in terms of different relations. The revealed specific features of the relaxation dynamics of the EEG parameters are analyzed in the age-related aspect. The influence of higher structures of the CNS and puberty-related rearrangements in the system of neuroendocrine regulation on the effectiveness of the regulatory function is discussed.     

Relationships between Cerebral Blood Flow Dynamics and Bioelectric Activity of the Human Brain in Experimental Acute Hypoxia

The relationships between the parameters of oxygen content in the body (hemoglobin saturation with oxygen and trancutaneous oxygen tension), central hemodynamics (cardiac output), and cerebral hemodynamics (cerebral blood flow rate) were studied during a hypoxic test (inhalation of an oxygen–nitrogen mixture containing 8% oxygen for 15 min). Special attention was paid to the relationships between the dynamics of cerebral blood flow and cerebral bioelectric activity measured by EEG parameters. It was demonstrated that the trancutaneous oxygen tension decreased to a greater extent than the hemoglobin saturation with oxygen and the cerebral blood flow increased to a greater extent than the cardiac output. The increase in cerebral blood flow and the increase in the indices and power of and EEG waves in the course of hypoxia were strongly positively correlated with each other in most subjects. However, if these parameters were considered in the series of subjects, the degree of the increase in the indices and power of and waves in different subjects was negatively correlated with the increase in the cerebral blood flow. The results are explained in terms of redistribution of blood flow in the body to provide a better oxygen supply to the brain and optimization of the ratios between the cerebral oxygen consumption and the functional load on the system of oxygen supply.     

Age and the structural organization of the EEG of children and adolescents in different functional states of the brain

The present paper deals with age characteristics of EEG reactions, at the level of integral cues, to functional loads in children of 7-14 years and juveniles. Modelling of tense and emotional states leads to a reconstruction of the organization of the EEG of quiet waking state, with formation of integral characteristics specific for these states and reflecting various mechanisms of the brain activity. At the age of 9-12 years emotional loads bring about disturbances of EEG integral characteristics, testifying to a lowering of brain reactivity.     

Neurophysiologial Study of the Hemispheric Organization of the EEG Spectrum in Mental Infantilism in Adolescents

Sixteen adolescents between 15 to 17 years of age with mental infantilism syndrome participated in the study. The data were compared with the control group including 10 mentally and neurologically healthy young subjects, secondary-school students in the 10th or 11th grades. The EEG was recorded monopolarly from 12 leads in the states of quiet wakefulness (closed eyes), on general activation (open eyes), when performing cognitive hemispheric-specialized tests, and when exposed to aversive sound stimulation. The studies showed that EEG spectral parameters could be regarded as the objective criteria of mental infantilism. In the baseline, the patients demonstrated the EEG characteristics typical of the earlier ontogenesis stage, i.e., a generalized increase in the spectral powers of -, ₁-, ₂-, and ₁-ranges and a decrease in the interhemispheric coherence in the frontal temporal region. When performing cognitive hemispheric-specialized tests, infantile patients were characterized by the insufficient differentiation of reactions to functional loads in terms of the frequency ranges, topography, and lateralization of changes, with the predominance of shifts in the ₂-range that is directly connected with nonspecific aspects of activation. On the presentation of sound stimulation, only the patients' group demonstrated an increase in the power of slow EEG ranges and interhemispheric coherence in the frontal temporal area. The results demonstrate the delayed formation of hemispheric specialization with a more retarded maturation of the nervous networks of the left hemisphere and the dysfunction of the frontal temporal regions of the brain.     

Intraserosal proximal hemideferentectomy versus classical proximal hemivasectomy in the rat. Anatomo-functional aspects and proposal for a new terminology

According to new trends and terms in microsurgery, the intra-serous proximal hemideferentectomy is compared to the classical vasectomy in rat. The effects of these surgical models are evaluated on morphological and functional bases. The anatomo-pathological parameters considered (stenosis and leakage of the anastomosis of the epididymal tubule conseguent on local ischemia) have been correlated with functional parameters "in vitro" (spontaneous motility and field stimulation) in order to plan the best microsurgical procedure in the experimental tubulo-vasostomy.     

EEG Spectral Characteristics in Junior Schoolchildren with Learning Problems

EEG spectral characteristics were studied in two age groups (7–8.5 and 8.5–10 years) of mentally healthy children and children with learning problems at rest and during performance of a Raven test. It was shown that slow frequencies are more pronounced in the EEG of 7- to 8.5-year-old children with learning problems than in EEG of healthy children of the same age group. An immature form of EEG activation, i.e., an increase not only in the but also in the frequencies during activity, was characteristic of these children. The reaction of the activation of the definitive type develops between the 8.5–10 years of age. This reaction is correlated with an increase in the efficiency of the sensory perceptive and sensorimotor activity. The distinctive feature of children with learning problems between 8.5–10 years of age is a greater expression of slow frequencies in the baseline EEG of the frontal (in particular, left frontal) areas of the cortex. The obtained results are considered as a reflection of a retardation of the functional maturation of the brain structures responsible for the deficit of involuntary and voluntary attention and the disorder of a systemic organization of perception and analytical–synthetic brain activity as compared to the normal age characteristics. Possible neurophysiological mechanisms responsible for learning problems in junior schoolchildren are discussed on the basis of the obtained results and evidence from the literature.     

Influence of Short-Term Relaxation on the Organization of the Brain Electrical Activity of Young Schoolchildren in the State of Quiet Wakefulness

Relaxation-induced changes in characteristics of the functional state of the nervous system (EEG parameters and electrodermal resistance (EDR)) were studied in 30 schoolchildren aged 9–10 years. A multichannel EEG was recorded from the occipital, parietal, temporo-parieto-occipital, central, and frontal areas of both brain hemispheres in three test conditions: quiet wakefulness, R, and recovery of the initial state. Simultaneously, the EDR was monitored. EEG amplitude spectra and coherence were calculated. Prior to and after relaxation, a cognitive test to determine the extent of short-term auditory verbal memory was performed. While changes in the EDR were reversible, relaxation-induced changes in the EEG parameters persisted after relaxation in many subjects. Changes in EEG coherence between distant derivations were most stable. Since short-term auditory verbal memory improved after relaxation, the postrelaxation changes in the EEG parameters were considered to reflect positive changes arising in the brain function and increasing the efficiency of cognitive processes.