Peculiarities of disorders of brain bioelectrical activity spatial-time organization in patients with different consciousness depression after severe head injury

Specific changes of bioelectrical brain activity was found in 27 patients with different level of posttraumatic consciousness depression by the methods of crosscorrelation, coherence and factor analysis of EEG. The changes of activity of morphofunctional systems of intracerebral integrations were revealed partially by decreasing of unspecific activity from brainstem structures reflected with increasing of slow wave activity and decreasing of EEG coherence in alpha- and beta-range. Depression of system organization of interconnections of bioelectrical brain activity in frontal and occipital regions of both hemispheres was also detected, and testified about decreasing of intercortical and thalamocortical brain system action under brain dislocation. The changes of integrative brain system activity, provides interhemispheric interaction, had the specific characted. Our results propose a "facilitation" of activity of system, providing "direct" interhemispheric connections through corpus callosum and other commissural tracts of telencephalon as a sequel of mesodiencephalon structures depression with steady reciprocal, antiphase relations of slow weve activity in symmetrical areas of hemispheres in coma II patients. The data of our research had shown no complete disintegration of system brain activity in coma II patients in spite of consciousness and brainstem reflexes depression.     

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.     

Alterations in Cortical Morphology after Neonatal Stroke: Compensation in the Contralesional Hemisphere?

Although neonatal arterial ischemic stroke is now well‐studied, its complex consequences on long‐term cortical brain development has not yet been solved. In order to understand the brain development after focal early brain lesion, brain morphometry needs to be evaluated using structural parameters. In this work, our aim was to study and analyze the changes in morphometry of ipsi‐ and contralesional hemispheres in seven‐year‐old children following neonatal stroke. Therefore, we used surface‐based morphometry in order to examine the cortical thickness, surface area, cortical volume, and local gyrification index in two groups of children that suffered from neonatal stroke in the left (n = 19) and right hemispheres (n = 15) and a group of healthy controls (n = 30). Reduced cortical thickness, surface area, and cortical volumes were observed in the ipsilesional hemispheres for both groups in comparison with controls. For the group with left‐sided lesions, higher gyrification of the contralesional hemisphere was observed primarily in the occipital region along with higher surface area and cortical volume. As for the group with right‐sided lesions, higher gyrification was detected in two separate clusters also in the occipital lobe of the contralesional hemisphere, without a significant change in cortical thickness, surface area, or cortical volume. This is the first time that alterations of structural parameters are detected in the “healthy” hemisphere after unilateral neonatal stroke indicative of a compensatory phenomenon. Moreover, findings presented in this work suggest that lesion lateralization might have an influence on brain development and maturation.     

Asymmetry of aging of the large hemispheres of the rat brain

The dynamics of the accumulation of free-radical oxidation products in the brain hemispheres of rats in rate ontogenesis was studied. Multiphase changes in the concentration of products in the right and left hemispheres in different age groups were registered. Significant differences in the contents of hydroperoxides, Schiff's bases of phospholipids and lipofuscin in brain hemispheres revealed, which correlates with different rate of ageing of hemispheres.     

The effect of the cingulate cortex on the development of the frontal lobe in the human

In the study, measurements of cortical structures of the medial surfaces of cerebral hemispheres of adults were taken. Its aim was to test whether the examined values were correlated with one another, and if so, then to what degree. Studies were conducted on 100 brains of adult people. It was assumed that the span of the corpus callosum (the genual retrosplenial length) of the left and the right hemisphere of the given brain was constant. The results of measurements and their statistical analysis prove that in both hemispheres the parameters concerning the cingulate gyrus, mainly of its paragenual width, are situated within the limits of significance. The mean values of the length of this gyrus were bigger on the left hemisphere. Differences in size of the hemispheres appeared to be statistically insignificant. The mean arithmetic values of the fronto-occipital distance of the hemispheres were greater for the right hemisphere. The results suggest that certain changes in the values of the frontal lobes depend on changes in values concerning the cingulate gyrus. This fact may confirm suggestions of certain authors that limbic structures of man, encompassing also the cortex of the cingulate gyrus, are not retarded and that their effect on the development of the frontal lobes may be as considerable as the one of the gyri.     

Magnetic-stimulation-related physiological artifacts in hemodynamic near-infrared spectroscopy signals

Hemodynamic responses evoked by transcranial magnetic stimulation (TMS) can be measured with near-infrared spectroscopy (NIRS). This study demonstrates that cerebral neuronal activity is not their sole contributor. We compared bilateral NIRS responses following brain stimulation to those from the shoulders evoked by shoulder stimulation and contrasted them with changes in circulatory parameters. The left primary motor cortex of ten subjects was stimulated with 8-s repetitive TMS trains at 0.5, 1, and 2 Hz at an intensity of 75% of the resting motor threshold. Hemoglobin concentration changes were measured with NIRS on the stimulated and contralateral hemispheres. The photoplethysmograph (PPG) amplitude and heart rate were recorded as well. The left shoulder of ten other subjects was stimulated with the same protocol while the hemoglobin concentration changes in both shoulders were measured. In addition to PPG amplitude and heart rate, the pulse transit time was recorded. The brain stimulation reduced the total hemoglobin concentration (HbT) on the stimulated and contralateral hemispheres. The shoulder stimulation reduced HbT on the stimulated shoulder but increased it contralaterally. The waveforms of the HbT responses on the stimulated hemisphere and shoulder correlated strongly with each other (r = 0.65–0.87). All circulatory parameters were also affected. The results suggest that the TMS-evoked NIRS signal includes components that do not result directly from cerebral neuronal activity. These components arise from local effects of TMS on the vasculature. Also global circulatory effects due to arousal may affect the responses. Thus, studies involving TMS-evoked NIRS responses should be carefully controlled for physiological artifacts and effective artifact removal methods are needed to draw inferences about TMS-evoked brain activity.     

Features of the organization of the cerebral cortex bioelectric potentials and visceral state in neurotic depression

Studies were conducted with the participation of 20 patients with different classical variants of neurotic depression. The spatial organization of the bioelectrical activity of the brain was studied with the method of cross-correlation and coherent analysis. The autonomic-visceral state was assessed by the results of the auricular cryoreflex test (measurement of the cold sensibility of auricular points). The clinical picture of neurotic depression was shown to be reflected in the structure of the EEG spatial organization, which is modified depending on the degree of neurotic depression and the concomitant anxiety and asthenic syndromes. In the group with depressive syndrome without concomitant asthenic or anxiety manifestations, most changes were revealed in the right frontotemporal-left posterotemporal region. A cross-correlation and coherence decrease in the frontotemporal regions of both hemispheres and markedly increased cross-correlations in the right posterotemporal region were revealed in the depression + associated anxiety group. In the group where the depressive and anxiety syndromes were associated with marked asthenic manifestations, decreased cross-correlation and coherent relations in the frontotemporal regions of both hemispheres were observed. The clinical picture of neurotic disorders is reflected in a specific pattern of variations in the spatial organization of electrical activity of the cerebral cortex and in variations in the autonomic visceral state parameters. The development of negative emotional states in humans is accompanied by changes in the visceral functions. Variations in the central brain structures involve the zones of representation of emotional reactions and the zones of cortical representation of the organs. Insignificant central variations may cause autonomic dysfunction.     

MAO, COMT, and GABA-T Activities in Primary Astroglial Cultures

Cultures from cerebral hemispheres of newborn rats contain the enzymes monoamine oxidase (MAO), catechol-O-methyltransferase (COMT), and gamma-aminobutyric acid alpha-ketoglutarate transaminase (GABA-T). The COMT activity was higher in the cultures than in adult rat cerebral hemispheres. The MAO activity was comparable in the cultures and in the rat cerebral hemispheres. The activities of both these enzymes increased with age in the cultures and in the rat brain hemispheres. In the culture the activities were further potentiated by removal of fetal calf serum and addition of 0.1 mM dibutyryl-cyclic AMP (dB-cAMP). GABA-T activity was, however, lower in the cultures than in the adult rat brain hemispheres. The activity increased in brain during postnatal maturation. No changes in the enzyme activity were observed in the cultures, either during growth or after removal of fetal calf serum and addition of dB-cAMP.     

Evaluation of Resting State Networks in Patients with Gliomas: Connectivity Changes in the Unaffected Side and Its Relation to Cognitive Function

In this study, we investigated changes in resting state networks (RSNs) in patients with gliomas located in the left hemisphere and its relation to cognitive function. We hypothesized that long distance connection, especially between hemispheres, would be affected by the presence of the tumor. We further hypothesized that these changes would correlate with, or reflect cognitive changes observed in patients with gliomas. Resting state functional MRI datasets from 12 patients and 12 healthy controls were used in the analysis. The tumor’s effect on three well-known RSNs including the default mode network (DMN), executive control network (ECN), and salience network (SN) identified using independent component analysis were investigated using dual regression analysis. Scores of neuropsychometric testing (WAIS-III and WMS-R) were also compared. Compared to the healthy control group, the patient group showed significant decrease in functional connectivity in the right angular gyrus/inferior parietal lobe of the ventral DMN and in the dorsolateral prefrontal cortex of the left ECN, whereas a significant increase in connectivity in the right ECN was observed in the right parietal lobe. Changes in connectivity in the right ECN correlated with spatial memory, while that on the left ECN correlated with attention. Connectivity changes in the ventral DMN correlated with attention, working memory, full IQ, and verbal IQ measures. Although the tumors were localized in the left side of the brain, changes in connectivity were observed in the contralateral side. Moreover, these changes correlated with some aspects of cognitive function indicating that patients with gliomas may undergo cognitive changes even in the absence of or before the onset of major symptoms. Evaluation of resting state networks could be helpful in advancing our hodological understanding of brain function in glioma cases.     

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.     

Canges in the monoamine content in the cat brain in a unilateral lesion of the cerebral cortex]

A spectrofluorometric study of the changes in serotonin and noradrenalin content was carried out in the cortex of large hemispheres, the hypothalamus and the midbrain on the 5th-6th day after creation of a pathological focus in the area of the occipital portion of the cortex in 12 cats. Diffuse changes in the bioelectrical activity of the brain were revealed on the EEG at this period: there appeared peak-like variations and slow waves of increased amplitude. There was noted a marked decrease in serotonin content in the cortex of the large hemispheres with the prevalance of an effect in the area directly adhering to the focus of affection. A tendency to reduction in serotonin level was revealed in the hypothalamus and the midbrain. The content of noradrenalin in the mentioned structures of the brain showed no significant change. The significance of the serotoninergic structures of the brain in the mechanisms participating in the restoration of the functional condition of the brain after its experimental injury is discussed.     

Role of the Right- and Left-Hemispheric Structures in Speech and Memory Formation in Children

The role of structures of the left and right cerebral hemispheres in formation of speech function and memory was studied on the basis of complex examination of children with developmental speech disorders. On the basis of EEG estimation of the functional state of the brain, children were classified in two groups depending on the side of localization of changes in electrical activity: those with local changes in electrical activity in the left hemisphere (group I) and those with changes in the right hemisphere (group II). The medical history suggested that the observed features of topography of local changes in electrical activity were linked with the character of prenatal and labor complications and their consequences leading to embryo- and ontogenetic disorders in development of different brain regions. Comparison of the results of neuropsychological examination of the two groups showed that different regions of the brain cortex of both the left and right hemispheres are involved in speech formation. However, a specific role of the right hemisphere in formation and actualization of automatic speech series was revealed. It was suggested that the integrity of gnostic functions of the right hemisphere and, primarily, the spatial organization of perception and movements is a necessary factor of development of auditory–speech and nominative memory.     

[1-13C]Glucose Metabolism in the Tumoral and Nontumoral Cerebral Tissue of a Glioma-Bearing Rat

C6 cells were used to establish a glioma-bearing rat model by stereotaxic injection in the left caudate nucleus. The tumor status was evaluated by magnetic resonance imaging and conventional histology. The glioma-bearing rats were infused for 1 h with a [1-(13)C]glucose solution. Perchloric acid extracts of the tumor and the ipsilateral and contralateral hemispheres were analyzed by 13C-NMR spectroscopy. The 13C-labeling patterns in compounds, mainly amino acids, indicated no drastic modification of carbon metabolism in both ipsilateral and contralateral hemispheres, as compared with control rats, whereas profound metabolic differences between brain tissue and tumor were observed. Glutamine C4 enrichment was lower in the glioma than in the brain [mean +/- SD values, 5.4 +/- 2.3 (n = 5) and 15.0 +/- 0.8% (n = 10), respectively] and also lower than the glutamate C4 enrichment in the glioma (mean +/- SD value, 22.6 +/- 4.2%; n = 5), indicating that tumor glutamine was neither synthesized inside the glioma nor taken up from the surrounding brain. The glutamine C4 enrichment in the serum (6.7 +/- 0.5%; n = 10) suggested that the glioma imported glutamine from the blood, a process probably connected with angiogenesis.     

A computer model for learning processes and the role of the cerebral commissures

A computer model of the two brain hemispheres is constructed of discrete populations of neurons, and it is shown to exhibit the characteristics of the great cerebral commissures, as has been pointed out by Sperry and others. For the range of parameters used we find that such systems respond in a specific manner to specific stimuli, and furthermore, whatever memory is transferred to one simulated hemisphere is also transferred to the other. However, this behavior changes when the two hemispheres are separated. We find that memory is not transferred from one hemisphere to the other when the interconnecting commissures are severed. The above findings verify Sperry's experimental observation that the split brain behaves as if it were indeed two separate brains, each performing concurrently and simultaneously diametrically opposite tasks.     

Features of the organization of biopotentials of a cerebral cortex and visceral status at the person at neurotic depression

Researches are spent on 20 patients with various clinical variants of neurotic depression. The regional organization of bioelectric activity of a brain by a method cross-correlation and coherent analysises was studied. Vegetovisceral status was studied by auricular criotest (measuring of cold sensibility of auricular points). It is shown, that the clinical picture of neurotic depression finds reflectance in frame of regional organization EEG. Regional organization EEG is modified depending on a degree of manifestation of the most neurotic depression and concomitant syndromes of alarm and an asthenia. In bunch with a depressive syndrome without concomitant asthenic and disturbing exhibitings the maximum changes are taped in the right frontotemporal range--left posttemporal ranges. In bunch where along with depression the alarm--depression cross-correlation and coherent communications frontotemporal ranges of both hemispheres was taped, strongly pronounced rising cross-correlation attitudes in right occipital ranges. In bunch where depressive and disturbing syndromes were combined with the expressed asthenic exhibitings, depression cross-correlation and coherent communications in frontotemporal ranges of both hemispheres was observed. The clinic of neurotic infringements finds reflection in a specific picture of variations of the spatial organization of electric activity of a brain and in variations of parameters of the vegetovisceral status. Realization of negative emotional conditions at the person is accompanied by variations visceral functions. Thus variations in the central brain structures cover zones of representation of emotional reactions and the zones connected with cortical representation visceral functions. The minimal central regulation, even insignificant central variations can cause vegetovisceral dysfunctions.     

Effect of low doses of gamma-hydroxybutyric acid on serotonin,noradrenaline, and dopamine concentrations in rat brain areas

The effects of intraperitoneal administration of gamma-hydroxybutyric acid (GHB) on biogenic amine levels in hemispheres, hypothalamus, midbrain, and medulla-pons, and on tryptophan in serum and brain, were studied. One hour after GHB administration (50 and 100 mg/kg) significant increases of dopamine concentration were observed in the hemispheres with both doses and in the hypothalamus with the higher dose, but a significant decrease of noradrenaline in the hypothalamus. No significant changes of serotonin metabolism were observed. These results indicate that low doses of GHB selectively affect the catecholaminergic neuronal activity.     

Intermolecular effects in the polymerization of hemoglobin S

Monolayer cultures of astrocytes from newborn rat brain hemispheres have been analysed for the glial-specific protein S-100, during their growth cycle. In primary cultures S-100 protein level increases with a pattern close to that observed with rat brain hemispheres $\text{in vivo}$. This finding suggests that some biochemical maturation of the astrocytes occurs $\text{in vitro}$. In secondary cultures the level of S-100 protein decreases and then increases at the end of the proliferation phase. This modulation, similar to that observed in a clonal culture of tumor cells from rat brain (C6) provides a model to study the relationship between gene expression and the phase of growth of the cells and will allow parallel investigations in normal and tumor cells.     

Effect of four mutations (Cr,S,S(H),h) in genes for mink coat color on brain monoamine oxidase]

Activity of A and B types of monoamine oxidase (MAO) has been investigated in the brain stem and brain hemispheres of mink males of five genotypes for coat-color mutations: standard dark-brown (+/+); heterozygous for the semidominant mutation Black crystal (Cr/+); homozygous for the semidominant mutation Black cross, or "95% White" (S/S); heterozygous for the semidominant mutation Shadow (SH/+); and homozygous for the semirecessive mutation hedlum white (h/h). The main changes in the activity of the A and B MAO types occur in the brain hemispheres. A reduced activity of MAO A has been recorded in the hemispheres of Black crystal minks (Cr/+) and an elevated activity, in the hemispheres of Shadow (SH/+) and 95% White (S/S). The activity of MAO B is reduced in the hemispheres of Black crystal and elevated in the hemispheres of hedlum white (h/h). An increased MAO A activity has also been recorded in the brain stem of Shadow minks (SH/+). It is suggested that genes controlling coat color have a pleiotropic effect on sexual behavior in males and the endocrine function of testicles mediated by a putative change in the metabolism of brain neurotransmitters, substrates of MAOs A and B.     

Disorders of the spatiotemporal organization of the brain’s bioelectrical activity in patients with different depressions of consciousness after severe head injury

Specific changes in the bioelectrical activity of the brain have been found in 27 patients with different levels of posttraumatic consciousness depression (stupor, spoor-coma I, coma II) by the methods of cross correlation, and coherence and factor EEG analysis. The changes in activity of the morphofunctional systems of intracerebral integrations were expressed partly in a decrease in the nonspecific activating effects from brainstem structures, which was reflected in an increase in the slow wave activity along with a considerable decrease in the level of EEG coherence in the α and β ranges. The observed depression of the system’s organization of the interrelations of the bioelectrical brain activity in the frontal and occipital regions of both hemispheres could be due to a decreased activity of the associative systems of intercortical and thalamocortical integration. The results suggest a certain facilitation of the activity of the system providing direct interhemispheric connections through the corpus calossum and other commissural tracts of the telencephalon as a consequence of the depression of the mesodiencephalon structures (which normally largely contribute to the synergistic interhemispheric interaction via synchronous ascending effects on the cortex of both hemispheres). This results in steady, reciprocal, and almost antiphase relations of slow wave activity in symmetrical areas of the hemispheres.     

Overhauser-enhanced magnetic resonance imaging characterization of mitochondria functional changes in the 6-hydroxydopamine rat model

Oxidative stress may be involved in the dopaminergic neurodegenerations seen in 6-OHDA-lesioned rats through its production of free radicals and through mitochondrial dysfunction. In this study, we noninvasively demonstrate brain redox alterations in 6-OHDA-lesioned rats using Overhauser-enhanced magnetic resonance imaging (OMRI). The reduction rate of 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-l-oxyl (methoxycarbonyl-PROXYL), a redox-sensitive contrast agent, was used as an index of the redox status in vivo. The methoxycarbonyl-PROXYL reduction rate, calculated from continuous images, decreased significantly in lesioned hemispheres compared to their corresponding contralateral hemispheres. The reduction rates in cellular fractions obtained from the striatum were estimated by X-band electron spin resonance (ESR) and calculated by assuming first-order kinetics for their time-dependent decreases. When methoxycarbonyl-PROXYL was mixed with cytoplasm fractions, the reduction rates were the same in both hemispheres. However, the ESR signal of methoxycarbonyl-PROXYL in the mitochondrial fraction of the lesioned hemispheres decayed more slowly than that of the corresponding contralateral hemispheres. Concordantly, biochemical assays showed that the activity of mitochondrial complex I also decreased more slowly in lesioned hemispheres. Thus, this method of noninvasively imaging brain redox alterations faithfully reflects changes in mitochondrial complex I activity in 6-OHDA-lesioned rats.