Relationship between EEG power and rhythm synchronization in health and cognitive pathology

We report here studies of comparative measures of spectral density and cortical interactions in EEG rhythms in health and schizophrenia. In healthy subjects, all rhythms were symmetrical and synchronous. In “acute” schizophrenia, unlike the situation in health, there was asymmetry (predominantly right-sided) in the distribution of the spectral power of EEG rhythms. In chronic patients, asymmetry was less marked, though the power of most EEG rhythms was significantly lower than in the other two study groups. “Acute” patients showed a lack of interhemisphere interactions for all rhythms apart from the alpha rhythm, while the number of cortical interactions in chronic patients was rather lower than that in the “acute” patients, though there were significantly fewer than in healthy subjects. In addition, the gamma range showed only one interhemisphere association in the posterior areas. These neurophysiological characteristics may underlie a number of the impairments of mental activity in patients with schizophrenia. These data may also indicate that the linkage between power characteristics and synchronization of EEG rhythms is a necessary condition for normal perceptive and cognitive activity and the organization of behavior. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 55, No. 4, pp. 496–504, July–August, 2005.     

Electrophysiological characterization of the functional state of the brain in mental disturbances in workers involved in the clean-up following the chernobyl atomic energy station accident

Studies were carried out on 150 workers with mental disturbances, who had been involved in the clean-up of the Chernobyl atomic energy station accident. Visual and computer analyses of EEG traces from 43 workers were compared with traces from 17 healthy subjects and the comparison revealed that the most common features in workers were disorganization of the α-rhythm and strengthening of β-1-acitivity in the sensorimotor cortex. In neurosis-like syndromes (13 patients), there was a significant increase in the power of the α-rhythm in the anterior parts of the cortex; in psycho-organic states, power was significantly reduced (especially in the left hemisphere), contributing to the greater proportion of flat EEG traces in patients with psycho-organic syndromes as compared with other groups of patients. Most patients among the clean-up workers had increased assimilation of flashing light rhythms and weakening of non-specific and skin galvanic responses to a light stimulus. It was concluded that systemic CNS changes occurred in patients from the clean-up worker groups, especially in those with psycho-organic syndrome. State Scientific Center of Psychiatry and Narcology, Ministry of Health and the Medical Industry of the Russian Federation, Moscow. Translated from Zhurnal Nevrologii i Psikhiatrii imeni S. S. Korsakova, Vol. 96, No. 3, pp. 41–46, May–June 1996.     

Investigating the relationship between fetus EEG,respiratory, and blood pressure signals during maturation using wavelet transform

In this study, we introduce the fast wavelet transform as a method for characterizing maturational changes in electrocortical activity, respiratory activity, and blood pressure in fetal lambs in early (110–122 days), mid (123–135 days), and late (136–144 days) third trimester (term 145 days). Each recording was 2 hr in duration. Wavelet decomposition was performed for six sets of parametersD _2j where 1≤j≤6. The six series wavelet transforms represent the following signal frequency bands: 1. 16–32 Hz; 2. 8–16 Hz; 3. 4–8 Hz; 4. 2–4 Hz; 5. 1–2 Hz; 6. 0.5–1 Hz. In the early group, power in the electrocephalogram (EEG) was highest in the fourth wavelet band, with relatively low power in the other bands. Increase in gestational age was characterized by increased power in all four wavelet bands. Power in the first wavelet band was significantly increased during low-voltage fast activity (LVFA) in the late group. The respiratory and blood pressure signals showed common frequency components with respect to time and were coincident with the LVFA EEG signal. Respiratory activity was only observed during some of the LVFA periods and was completely absent during high-voltage slow activity (HVSA) EEG. The respiratory signal showed dominant power in the fourth wavelet band, and less power in the third and fifth band. The blood pressure signal was also characterized by dominant power in the fourth wavelet band. This power was significantly increased during periods of respiratory activity. These results suggest a strong relationship between fetal EEG, blood pressure, and breathing movements.     

Handedness leads to interhemispheric EEG asymmetry during sleep in the rat

Sleep electroencephalographic (EEG) slow-wave activity is increased after wakefulness and decreases during sleep. Regional sleep EEG differences are thought to be a consequence of activation of specific cortical neuronal circuits during waking. We investigated the relationship between handedness and interhemispheric brain asymmetry. Bilateral EEG recordings were obtained from the frontal and occipital cortex in rats with a clear paw preference in a food-reaching task (right, n = 5; left, n = 5). While still na?ve to the task, no waking or sleep EEG asymmetry was present. During the food-reaching task, the waking EEG showed significant, substantial power increases in the frontal hemisphere contralateral to the dominant paw in the low theta range (4.5-6.0 Hz). Moreover, the non-REM sleep EEG following feeding bouts was markedly asymmetric, with significantly higher power in the hemisphere contralateral to the preferred paw in frequencies >1.5 Hz. No asymmetry was evident in the occipital EEG. Correlation analyses revealed a positive association between the hemispheric asymmetry during sleep and the degree of preferred use of the contralateral paw during waking in frequencies <9.0 Hz. Our findings show that handedness is reflected in specific, regional EEG asymmetry during sleep. Neuronal activity induced by preferential use of a particular forelimb led to a local enhancement of EEG power in frequencies within the delta and sigma ranges, supporting the hypothesis of use-dependent local sleep regulation. We conclude that inherent laterality is manifested when animals are exposed to complex behavioral tasks, and sleep plays a role in consolidating the hemispheric dominance of the brain.     

Effect of new anxiolytic CM-346 on bioelectrical activity of cerebral cortex in MR and MNRA rats

The effect of 2-[2-(morpholin)ethylthio]-5-ethoxybenzimidazole (CM-346) on the EEG of MR and MNRA rats was compared with that of diazepam. Both CM-346 and diazepam reversed stress-induced changes in bioelectrical activity after intraperitoneal injection of 0.9% NaCl. In MR and MNRA rats both drugs decreased the EEG spectral power in the high-frequency θ-band (7.5–8.2 Hz). In MR rats, CM-346 increased the power of the low-frequency θ-rhythm (4.8–5.8 Hz) and the dominant activity peak (6.0–7.2 Hz) and decreased the spectral power in the 19–20 Hz band. The data suggest that CM-346 exerts antistressor and anxiolytic effects in animals with passive reactions to emotional stress. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 128, No. 11, pp. 500–503, November, 1999     

Music Therapy Modulates Fronto-Temporal Activity in Rest-EEG in Depressed Clients

Fronto-temporal areas process shared elements of speech and music. Improvisational psychodynamic music therapy (MT) utilizes verbal and musical reflection on emotions and images arising from clinical improvisation. Music listening is shifting frontal alpha asymmetries (FAA) in depression, and increases frontal midline theta (FMT). In a two-armed randomized controlled trial (RCT) with 79 depressed clients (with comorbid anxiety), we compared standard care (SC) versus MT added to SC at intake and after 3 months. We found that MT significantly reduced depression and anxiety symptoms. The purpose of this study is to test whether or not MT has an impact on anterior fronto-temporal resting state alpha and theta oscillations. Correlations between anterior EEG, Montgomery–Åsberg Depression Rating Scale (MADRS) and the Hospital Anxiety and Depression Scale—Anxiety Subscale (HADS-A), power spectral analysis (topography, means, asymmetry) and normative EEG database comparisons were explored. After 3 month of MT, lasting changes in resting EEG were observed, i.e., significant absolute power increases at left fronto-temporal alpha, but most distinct for theta (also at left fronto-central and right temporoparietal leads). MT differed to SC at F7–F8 (z scored FAA, p < .03) and T3–T4 (theta, p < .005) asymmetry scores, pointing towards decreased relative left-sided brain activity after MT; pre/post increased FMT and decreased HADS-A scores (r = .42, p < .05) indicate reduced anxiety after MT. Verbal reflection and improvising on emotions in MT may induce neural reorganization in fronto-temporal areas. Alpha and theta changes in fronto-temporal and temporoparietal areas indicate MT action and treatment effects on cortical activity in depression, suggesting an impact of MT on anxiety reduction.     

Changes in electroencephalographic power and bicoherence spectra according to depth of dexmedetomidine sedation in patients undergoing spinal anesthesia

Background: Assessment the depth of dexmedetomidine sedation using electroencephalographic (EEG) features can improve the quality of procedural sedation. Previous volunteer studies of dexmedetomidine-induced EEG changes need to be validated, and changes in bicoherence spectra during dexmedetomidine sedation has not been revealed yet. We aimed to investigate the dexmedetomidine-induced EEG change using power spectral and bicoherence analyses in the clinical setting.Patients and Methods: Thirty-six patients undergoing orthopedic surgery under spinal anesthesia were enrolled in this study. Dexmedetomidine sedation was conducted by the stepwise increase in target effect site concentration (Ce) while assessing sedation levels. Bispectral index (BIS) and frontal electroencephalography were recorded continuously, and the performance of BIS and changes in power and bicoherence spectra were analyzed with the data from the F3 electrode.Results: The prediction probability values for detecting different sedation levels were 0.847, 0.841, and 0.844 in BIS, 95% spectral edge frequency, and dexmedetomidine Ce, respectively. As the depth of sedation increased, δ power increased, but high β and γ power decreased significantly (P <0.001). α and spindle power increased significantly under light and moderate sedation (P <0.001 in light vs baseline and deep sedation; P = 0.002 and P <0.001 in moderate sedation vs baseline and deep sedation, respectively). The bicoherence peaks of the δ and α-spindle regions along the diagonal line of the bicoherence matrix emerged during moderate and deep sedation. Peak bicoherence in the δ area showed sedation-dependent increases (29.93%±7.38%, 36.72%±9.70%, 44.88%±12.90%; light, moderate, and deep sedation; P = 0.008 and P <0.001 in light sedation vs moderate and deep sedation, respectively; P = 0.007 in moderate sedation vs deep sedation), whereas peak bicoherence in the α-spindle area did not change (22.92%±4.90%, 24.72%±4.96%, and 26.96%±8.42%, respectively; P=0.053).Conclusions: The increase of δ power and the decrease of high-frequency power were associated with the gradual deepening of dexmedetomidine sedation. The δ bicoherence peak increased with increasing sedation level and can serve as an indicator reflecting dexmedetomidine sedation levels.     

Interhemispheric EEG asymmetry in patients with insomnia during nocturnal sleep

Sleep EEG was recorded and analyzed in patients with neurotic insomnia. It was found that interhemispheric asymmetry in the same individual can vary during sleep from right-hemispheric to left-hemispheric. Interhemispheric EEG asymmetry is closely related to the stage of sleep. The development of left-hemisphere or right-hemisphere asymmetry is mainly determined by activity of the right hemisphere. The development of interhemispheric asymmetry during wakefulness, stages 1 and 2 sleep, and delta sleep is mediated by common mechanisms. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 141, No. 2, pp. 157–160, February, 2006     

Specificity of velocity in strength training

Summary Twenty-one male volunteers (ages 23–25 years) were tested pre- and post training for maximal knee extension power at five specific speeds (1.05, 2.09, 3.14, 4.19, and 5.24 rad·s⁻¹) with an isokinetic dynamometer. Subjects were assigned randomly to one of three experimental groups; group S, training at 1.05 rad·s⁻¹ (n=8), group I, training at 3.14 rad·s⁻¹ (n=8) or group F, training at 5.24 rad·s⁻¹ (n=5). Subjects trained the knee extensors by performing 10 maximal voluntary efforts in group S, 30 in group I and 50 in group F six times a week for 8 weeks. Though group S showed significant increases in power at all test speeds, the percent increment decreased with test speed from 24.8% at 1.05 rad·s⁻¹ to 8.6% at 5.24 rad·s⁻¹. Group I showed almost similar increment in power (18.5–22.4 at all test speeds except at 2.09 rad·s⁻¹ (15.4%). On the other hand, group F enhanced power only at faster test speeds (23.9% at 4.19 rad·s⁻¹ and 22.8% at 5.24 rad·s⁻¹).     

Effect of hypoxia of increasing severity on the dynamics of cerebral cortex EEGs in rats with different resistance to acute oxygen deficiency

EEGs recorded from the cerebral cortex of rats with high and low resistance to hypoxia during “elevation” in a pressure chamber differ in the dynamics of the EEG power spectra. EEGs of highly resistant rats show phasic changes in biopotentials correlating with the severity of hypoxia: primary increase in the absolute power of all frequency ranges is followed by normalization and a secondary increase with predominance of the slow-wave component, inhibition of the β₂ range and the emergence of interhemispheric differences, and terminal inhibition of the power of all frequency ranges. In rats with low resistance to hypoxia, phases of relative normalization of EEG spectra and their depression during terminal period are not observed, all changes being represented by a continuous increase in the power of the α and δ ranges with progressive inhibition of the β₂ range and then of the β₁ range. Interhemispheric asymmetry is significant throughout the period of power increase. A high amplitude burst activity is recorded in rats of both types starting from an altitude of 8000 or 9000 m. The pattern of EEG changes in rats exposed to hypoxia of growing severity consistently reproduces those observed in patients with ischemic stroke. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 9, pp. 262–267, September, 1996     

Characteristics of Neurological Status and the Electroencephalogram in Nuclear Power Station Control Operators

A total of 105 control operators at the Kursk nuclear power station were studied: 45 after working shifts (study group) and 60 on rest days (reference group). These investigations showed that operators’ work shifts had significant influences on the functional state of the nervous system, promoting the appearance or exacerbation of autonomic dysfunction. In some cases, work shifts increased arterial blood pressure to risk levels for the development of cerebrovascular disease. The effects of nuclear power station operators’ work shifts on brain bioelectrical activity included a decrease in the proportion of unaltered EEG traces, along with increases in the spectral power densities of the α rhythm in the parietal leads and the θ rhythm in the posterior temporal and parietal leads. The origin of these changes may be related to both fatigue and the effects of adverse industrial factors. It is suggested that clinical observation of power station operators should be supplemented by assessments of autonomic dysfunction and measurement of the spectral power densities of the α and θ rhythms in the parietal and posterior temporal leads.     

EEG power mapping,dipole source and coherence analysis in chernobyl patients

Summary EEG power mapping, coherence analysis, source localization of epileptiform activity and psychoneurological investigations were performed in 100 patients (males, 25–45 years old, right-handed), who took part in the cleaning of the Chernobyl disaster in 1986–1987, and compared with a control group (healthy persons of the same age). Neuropsychological studies showed autonomie, endocrine, emotional and other disorders in all patients. About 70% of all patients had paroxysmal EEG activity and intermittent seizures sometimes associated with loss of consciousness. EEG power mapping showed higher than normal levels of alpha- and theta-bands power, mainly in the frontal and central areas in the one group of patients. In others, power was lower especially in alpha-band. Paroxysmal waves of alpha- and theta-bands had localization of dipole sources at deeper near midline levels, and as a rule with a shift to the right hemisphere. Paroxysmal beta-waves demonstrated sources of a diffuse character at a more basal level with a shift to the left hemisphere. Interhemispheric coherences had lower values in the frontal and higher in the central leads than in healthy persons. Intrahemispheric coherences were decreased in the left hemisphere and increased in the right, opposite to that in controls.     

Attenuated asymmetry of functional connectivity in schizophrenia: A high‐resolution EEG study

The interhemispheric asymmetries that originate from connectivity‐related structuring of the cortex are compromised in schizophrenia (SZ). Under the assumption that such abnormalities affect functional connectivity, we analyzed its correlate—EEG synchronization—in SZ patients and matched controls. We applied multivariate synchronization measures based on Laplacian EEG and tuned to various spatial scales. Compared to the controls who had rightward asymmetry at a local level (EEG power), rightward anterior and leftward posterior asymmetries at an intraregional level (1st and 2nd order S‐estimator), and rightward global asymmetry (hemispheric S‐estimator), SZ patients showed generally attenuated asymmetry, the effect being strongest for intraregional synchronization in the alpha and beta bands. The abnormalities of asymmetry increased with the duration of the disease and correlated with the negative symptoms. We discuss the tentative links between these findings and gross anatomical asymmetries, including the cerebral torque and gyrification pattern, in normal subjects and SZ patients.     

Electro-encephalogram disturbances in different sleep-wake states following exposure to high environmental heat

In this study, cerebral electrical activity or electro-encephalogram (EEG) was studied following exposure to high environmental heat, in three different age groups of freely moving rats. Each age group was subdivided into three groups: the acute heat stress group, subjected to a single exposure of 4h at 38°C in the biological oxygen demand incubator; the chronic heat stress group, exposed for 21 days, for 1 h each day, at 38°C in the incubator; and the handling control group. The polygraphic sleep-wake recordings involved simultaneous recordings of cortical EEG, electrooculogram (EOG), and electromyogram (EMG), on paper and in digital form on computer hard disk, just after the heat exposure for the acute stressed rats and on the 22nd day for the chronic stressed rats. The power spectrum was calculated for 2s epochs of the EEG signals. Quantitative analyses of EEG (qEEG) showed that, in all three age groups, changes in higher-frequency components (β₂) were significant in all sleep-wake states following both acute and chronic heat stress conditions. The power of β₂ activity in all three age groups after acute heat exposure was significantly decreased during slow wave sleep (SWS) (p<0.05) and rapid eye movement sleep (p<0.05), whereas the reverse was observed in the awake state (p<0.05). Following chronic heat exposure, β₂ activity was found to increase in all three sleep-wake stages in all groups of rats (p<0.01 for SWS in the weaning group and p<0.05 for other data). Thus the study demonstrated that the cortical EEG is sensitive to environmental heat, and alterations in EEG frequencies in different states of mental consciousness due to high heat can be differentiated efficiently by EEG power spectrum analysis.     

Differences of brain electrical activity between moderate and severe obstructive sleep apneic patients: a LORETA study

The effects of initiation of continuous positive airway pressure (CPAP) therapy on electroencephalographic (EEG) background activity were investigated in patients exhibiting both moderate (n = 13) and severe (n = 12) obstructive sleep apnea syndromes in the testing of the potential differences of alterations of brain electrical activity caused by chronic hypoxia between these two groups. A normal control group (n = 14) was also examined. Two EEG examinations were achieved in each group: before and after first‐time CPAP therapy. Low‐resolution electromagnetic tomography (LORETA) was implemented towards localizing the generators of EEG activity in separate frequency bands. Prior to CPAP treatment, as a common direction of change, analysis with LORETA demonstrated increased activity in comparison with the patient and control groups. In the moderate group, significant changes were detected in the alpha2 band in the posterior cingulate cortex as well as in the beta1 band in the right posterior parietal cortex and the left supramarginal gyrus. In the severe group, significant changes were found in theta and alpha1 bands in the posterior cingulate cortex. Following CPAP treatment, these significant differences vanished in the severe group. In the moderate group, significantly decreased activity was seen in the beta3 band in the right fusiform gyrus. These findings potentially suggest a normalizing effect of CPAP therapy on EEG background activity in both groups of obstructive sleep apnea syndrome patients. Compensatory alterations of brain electrical activity in regions associated with influencing successful memory retrieval, emotional perception, default mode network, anorexia and fear network caused by chronic intermittent hypoxia could possibly be reversed with the use of CPAP therapy.     

Phasic increases in cortical beta activity are associated with alterations in sensory processing in the human

Oscillatory activity in the beta (β)-frequency band (13–35 Hz) can be recorded over the sensorimotor cortex in humans. It is coherent with electromyographic activity (EMG) during tonic contraction, but whether the cortical β-oscillations are primarily motor or sensorimotor in function remains unclear. We tested the hypothesis that cortical β-activity is associated with an up-regulation of sensory inputs that may be relevant to the organization of the motor response. We recorded cortical somatosensory potentials (SEPs) elicited by electrical stimuli to the median nerve at the wrist triggered by increases of electroencephalographic (EEG) β-activity in the contralateral fronto-central EEG and compared these to SEPs presented at random intervals. The involvement of motor cortex in the triggering EEG activity was confirmed by a simultaneous elevation of cortico-spinal synchrony in the β-band. The negative cortical evoked potential peaking at 20 ms and the positive evoked potential peaking at 30 ms after median nerve shocks were increased in size when elicited after phasic increases in β-activity. The functional coupling of sensory and motor cortices in the β-band was confirmed in recordings of electrocorticographic activity in two patients with chronic pain syndromes, suggesting a means by which β-activity may simultaneously influence cortical sensory processing, motor output and promote sensory-motor interaction. An erratum to this article can be found at     

Multiparameter Analysis of EEG in Old Wistar Rats after Bilateral Carotid Artery Ligation

We showed that 302 of 840 EEG parameters in old Wistar rats significantly change 3 h after bilateral carotid artery ligation. All animals (n=7) died 250±47 min after ligation. EEG power spectra had signs of suppression (increased δ-activity, decreased τ-activity, and increased low-frequency α-activity) or activation of CNS (decreased high-frequency α-activity and paroxysmal increase in β-activity). The coherence, synchrony, and entropy of potentials were reduced in the majority of brain regions. This method and scheme of experiments are suitable for the search and study of anti-stroke drugs.     

“Brain music” in the treatment of patients with insomnia

The effects of a new nonpharmacological method of treating insomnia—“brain music”—were studied. The method is based on the transformation of the EEG into music using a special algorithm developed by the authors. Sleep polygrams were recorded and analyzed, and EEG segments corresponding to different sleep phases were identified using standard criteria, and were transformed into music. Patients listened to the resulting audio cassettes before going to sleep. Clinical, questionnaire, psychological, and electrophysiological (polysomonographic, electroencephalographic) methods were used before and after 15-day treatment courses in 58 patients with insomnia, who were divided into two groups: group 1 (44 patients) formed the experimental group, and group 2 (14 patients) formed the “placebo” group (in whom the “brain music” of a different patient was used). “Brain music” was found to have positive effects in more than 80% of the insomniac patients both from the point of view of subjective sensations and in terms of objective studies, i.e. neuropsychological and neurophysiological investigations. The high efficacy of “brain music” in patients with insomnia was combined with an absence of side effects and complications. The material in this paper has been presented previously, at the Second International Meeting on Psychiatry and the Central Nervous System, November 2, 1994, Paris. Department of Nervous Diseases, Faculty of Postgraduate Professional Education and Center for Sleep Studies, I. M. Sechenov Moscow Medical Academy, Moscow City Sleep Center. Committee of Health of the Moscow City Council at A. A. Ostroumov City Clinical Hospital No. 33. Translated from Zhurnal Nevrologii i Psikhiatrii imeni S. S. Korsakova, Vol. 97, No. 4, pp. 39–43, April, 1997.     

Using EEG to Explore How rTMS Produces Its Effects on Behavior

A commonly held view is that, when delivered during the performance of a task, repetitive TMS (rTMS) influences behavior by producing transient “virtual lesions” in targeted tissue. However, findings of rTMS-related improvements in performance are difficult to reconcile with this assumption. With regard to the mechanism whereby rTMS influences concurrent task performance, a combined rTMS/EEG study conducted in our lab has revealed a complex set of relations between rTMS, EEG activity, and behavioral performance, with the effects of rTMS on power in the alpha band and on alpha:gamma phase synchrony each predicting its effect on behavior. These findings suggest that rTMS influences performance by biasing endogenous task-related oscillatory dynamics, rather than creating a “virtual lesion”. To further differentiate these two alternatives, in the present study we compared the effects of 10 Hz rTMS on neural activity with the results of an experiment in which rTMS was replaced with 10 Hz luminance flicker. We reasoned that 10 Hz flicker would produce widespread entrainment of neural activity to the flicker frequency, and comparison of these EEG results with those from the rTMS study would shed light on whether the latter also reflected entrainment to an exogenous stimulus. Results revealed pronounced evidence for “entrainment noise” produced by 10 Hz flicker—increased oscillatory power and inter-trial coherence (ITC) at the driving frequency, and increased alpha:gamma phase synchronization—that were nonetheless largely uncorrelated with behavior. This contrasts markedly with 10-Hz rTMS, for which the only evidence for stimulation-induced noise, elevated ITC at 30 Hz, differed qualitatively from the flicker results. Simultaneous recording of the EEG thus offers an important means of directly testing assumptions about how rTMS exerts its effects on behavior.     

Analysis of changes in the electroencephalogram power spectrum on a new model of brain ischemia in rats

The bioelectrical activity is studied in the left and right parietal cortex by recording the power spectrum of the electroencephalogram in brain ischemia caused by complete ligation of the left common carotid artery and 50% reduction of the blood flow in the right common carotid artery in experiments carried out on nonnarcotized Wistar rats. Ischemia results in marked and stable disorders in the bioelectrical activity manifested in a decrease of the total EEG power, depression of the dominating frequency in the Θ-range, increase of the δ-range power, and interhemispheric asymmetry of some spectrogram parameters. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny Vol. 118, N ^o 12, pp. 565–567, December, 1994 Presented by E. D. Gol'dberg, Member of the Russian Academy of Medical Sciences