Effects of Deprivation of the Quick-Wave Sleep in Rats with Inherited Predisposition to Audiogenic Convulsions

In experiments on rats of Krushinskii–Molodkina line (KM) with genetic predisposition to audiogenic convulsions, effects of the 3- and 6-h periods of the absence of the quick-wave sleep (QS) were studied in animals under natural conditions as well as of selective deprivations of QS on EEG spectral characteristics in the wakening–sleep cycle, on organization of the cycle, and on intensity of convulsive symptoms. The QS deprivation for 3, 6, 9, and 12 h was produced by the classic methods of small platforms or of soft awakening. The data are presented about changes of the cycle parameters in the course of natural and experimental deprivations as well as about the dynamics of restoration of the cycle structure for 12 h of the post-deprivation period. It was established that during and after the QS deprivations (by any duration), in EEG of the hippocampus, caudate nucleus, medial central nucleus of thalamus, somato-sensory, visual and auditory cortex of the KM rat brain, no appearance of the paroxysmal fires was revealed in any of the states of the wakening–sleep cycle. It was also found that the selective QS deprivation did not affect duration of the latent period and parameters of the generalized tonic-clonic audiogenic convulsions. It is stated that in rats of the KM line that have the hidden convulsive syndrome, the used kinds and methods of QS deprivation fail to activate the epileptiform manifestations.     

Electroencephalographic analysis of manifestations of latent forms of paroxysmal syndrome in the wakefulness-sleep cycle in rats

An electroencephalographic study of the brain activity in the wakefulness-sleep cycle was carried out on rats of Krushinskii-Molodkina line (KM) with hereditary predisposition to audiogenic convulsions and on Wistar rats that were insensitive to the convulsiogenic sound effect, but with epileptiform manifestations appearing on the background of cadmium intoxication and administration of kainic acid into the caudate nucleus head. There were revealed several EEG patterns whose presence was an indicator of formation of disorders of the CNS activity of the paroxysmal character in the animals. It has been established that in the phase of the rat rapid-wave sleep, a high representation of episodes with predominance of a-diapason EEG oscillations can be considered a specific non-paroxysmal abnormality due to the presence of convulsive syndrome in these animals. It was shown the long steady decrease of sensitivity of KM rats to the convulsiogenic sound effect, which appeared after multiple audiogenic generalized tonicoclonic convulsive attacks, correlated with a decrease of the degree of theta-diapason oscillations and with an increase of representation of alpha-diapason waves on EEG in the state of the animal quiet consciousness. A role of disintegration in activity of the ascending activating brain systems in the animal and human paroxysmal syndromes is discussed.     

Spectral analysis and mathematical modeling of electrical cerebral activity in rats with genetically determined predisposition to seizure and in controls

Spectral signs of genetically determined predisposition to seizure characteristic of Krushinskii-Molodkina (KM) strain rats were found when studying summated cerebral potentials, namely increased power of low (1–3 Hz) frequencies in spectra of motor and visual cortex potentials together with an abrupt increase and a reduction respectively in the power of hippocampal and caudate nucleus potentials. Comparative spectra of summated electrical activity within neuronal networks [10] and those of experimentally obtained potentials as determined by modeled parameters simulating neuronal networks were found (an inverse problem of modeling). It was found that spectral signs of predisposition to seizure could reflect changes in the physiological properties of neuronal networks belonging to the rat brain structures investigated. It might be suggested on the basis of the calculations performed that genetic predisposition to seizure in KM strain rats is determined by attenuation of the inhibitory function of the caudate nucleus and by heightened excitability (reactivity) in neurons of the paleo- and neocortex.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 184–193, March–April, 1990.     

Comparative analysis of EEG spatial organization in the rats with different level of genetically determinated anxiety under ethanol

The pecularities of EEG changes in the rats with geneticaly different level of anxiety was studed after ethanol injection. The biopotentials spatial synchronization and entropy in the "high anxious" rats (strain MR) did not increase under low dose; on the contrary the above changes were characteristic for the rats without anxiety signs (strain MNRA). After injection of middle and high ethanol doses the "high anxious" rats as compared with "low anxious" ones had the "simplification" of reaction type--the increase of narrow frequency coherence (i.e. linear biopotentials relationship) and spectral power of theta-activity (5.75-7.25 Hz), which was combined with the decrease of nonlinear biopotential characteristics. This fact is interpreted as the predominance of subcortical mechanisms of the brain functional state regulation over cortical ones. The significant decrease of high frequency EEG components in "high anxious" rats takes place under more high ethanol doses, presumably reflecting the increase of the anxiolytic level of ethanol effect.     

Effect of swinging on EEG of rats of juvenile age in the wakefulness state

Simultaneous recording of the EEG activity of superficial cortical and deep (caudate nucleus, dorsal hippocampus, anterior hypothalamus) brain parts has been performed for the first time after a 2-h swinging of frequency of 0.2 Hz in Wistar rats of juvenile age. Swinging was produced on a 4-bar parallel swing. Using a Neuron-Spectr electroencephalograph and a Diana program, normalized power spectra of wave EEG components, synchronization coefficients, and coefficients of cross-correlation between bioelectrical potentials of various brain structures were determined. After a 2-h swinging, the mean value of normalized power of slow waves of delta-diapason in hypothalamus and hippocampus was found to increase statistically significantly, while normalized power of fast waves of alpha- and beta1-diapasons in hippocampus decreased (p < 0.05). A statistically significant increase of synchronization coefficient was observed in hypothalamus and hippocampus. Changes of coefficients of cross-correlation between hypothalamus and hippocampus and other brain strictures were of the oppositely directed, individual character. In the parietal occipital brain cortex and in caudate nucleus, the changes of the EEG spectral composition also were of individual character. The obtained results on the whole correspond to data about an enhancement of the EEG low-frequency rhythms at swinging and agree with the resonance hypothesis of motion sickness.     

Electroencephalographic analysis of manifestations of hidden forms of paroxysmal syndrome in the wakefulness-sleep cycle in rats

An electroencephalographic study of the brain activity in the wakefulness-sleep cycle was carried out on rats of Krushinskii-Molodkina line (KM) with hereditary predisposition to audiogenic convulsions and on Wistar rats that were insensitive to the convulsiogenic sound effect, but with epileptiform manifestations appearing on the background of cadmium intoxication and administration of kainic acid into the caudate nucleus head. There were revealed several EEG patterns whose presence was an indicator of formation of disorders of the CNS activity of the paroxysmal character in the animals. It has been established that in the phase of the rat rapid-wave sleep, a high representation of episodes with predominance of α-diapason EEG oscillations can be considered a specific non-paroxysmal abnormality due to the presence of convulsive syndrome in these animals. There was shown a long steady decrease of sensitivity of KM rats to the convulsiogenic sound effect, which appeared after multiple audiogenic generalized tonicoclonic convulsive attacks, correlated with a decrease of the degree of ?-diapason oscillations and with an increase of representation of α-diapason waves on EEG in the state of the animal quiet wakefulness. The role of disintegration in activity of the ascending activating brain systems in the animal and human paroxysmal syndromes is discussed.     

Effects of total sleep deprivation in rats with hereditary predisposition to audiogenic convulsions

In rats of the Krushinskii-Molodkina (KM) line with hereditary predisposition to audiogenic convulsions there were studied effects of total sleep deprivation for 3, 6, and 9 h by a light arousal or a slow rotation in a roller on spectral EEG characteristics in the wakefulness-sleep cycle, organization of the cycle, and intensity of convulsive symptoms at the recovery period. The data are presented on dynamics of recovery of the cycle structure for 12 h of postdeprivation period. It has been established that during and after the total sleep deprivations of any duration no paroxysmal discharges appear in EEG of hippocampus, caudate nucleus, medial central thalamic nucleus, somatosensory, visual, and auditory cerebral cortex in any of states of the wakefulness-sleep cycle. These deprivations were also shown to have no effect on the latent period value and parameters of generalized tonic-clonal audiogenic convulsions. At the same time, after 6 and 9 h of the total sleep deprivations in a slowly rotating roller there was revealed in some animals a change of the type of response to the sound stimulus. Such decrease of reaction of rats to audiogenic stimuli seems to be due to alertness of the animals. It is stated that in the KM rats, with the hidden convulsive syndrome, we failed to activate epileptiform manifestations by the used types and ways of the total sleep deprivations.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 41, No. 1, 2005, pp. 82–88.Original Russian Text Copyright © 2005 by Vataev, Oganesyan.     

Effect of swinging on EEG of rats of juvenile age in the wakefulness state

Simultaneous recording of the EEG activity of superficial cortical and deep (caudate nucleus, dorsal hippocampus, anterior hypothalamus) brain parts has been performed for the first time after a 2-h swinging of frequency of 0.2 Hz in Wistar rats of juvenile age. Swinging was produced on a 4-bar parallel swing. Using a Neuron-Spectre electroencephalograph and a Diana program, normalized power spectra of wave EEG components, synchronization coefficients, and coefficients of cross-correlation between bioelectrical potentials of various brain structures were determined. After a 2-h swinging, the mean value of normalized power of slow waves of δ-diapason in hypothalamus and hippocampus was found to increase statistically significantly, while normalized power of fast waves of α-and β₁-diapasons in hippocampus decreased (p < 0.05). A statistically significant increase of synchronization coefficient was observed in hypothalamus and hippocampus. Changes of coefficients of cross-correlation between hypothalamus and hippocampus and other brain strictures were of the oppositely directed, individual character. In the parietal occipital brain cortex and in caudate nucleus, the changes of the EEG spectral composition also were of individual character. The obtained results on the whole correspond to data about an enhancement of the EEG low-frequency rhythms at swinging and agree with the resonance hypothesis of motion sickness.     

Spreading depression produced in the thalamus,hippocampus, and caudate nucleus by electrical stimulation of the parietal cortex in rats

The parameters of cortical electrical stimulation (ES) producing synaptically-operated spreading depression (SD) were determined in rats. Waves of SD were regularly triggered in the thalamus by brief, high frequency ES (0.02–0.05 sec; 200–500 Hz) of the parietal cortex. Monitoring by EEG confirmed the lack of accompanying convulsive activity in the cortex and the subcortical structures investigated. Use of Nembutal-induced anesthesia led to a higher minimum threshold for onset of SD, without preventing short-latency thalamid SD. Stimulating the parietal cortex was less effective for synaptic excitation of hippocampal and caudate SD. Hippocampal, unlike thalamic SD, was accompanied by spells of epileptiform activity, most pronounced at certain points in the onset and decline of the SD wave. These brief convulsive episodes were not the cause but the result of SD to a large extent. The low, subconvulsive threshold of synaptically triggered subcortical as well as cortical structures should therefore be taken into account when considering the functional significance of the SD reaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 36–44, January–February, 1990.     

Spectral analysis of EEG in normal rats and in rats genetically predisposed to seizures

Spectral and visual analyses were performed on the EEG of the motor and visual cortex, hippocampus, caudate nucleus, and intralaminary thalamic nuclei in two strains of rats; animals were maintained in a state of "awake immobility." It was found that KM rats, genetically predisposed to audiogenic fits, differed from the Wistar strain not subject to this genetic predisposition in that mean relative intensity of theta rhythm diminished and high amplitude slow irregular hippocampal activity intensified in the neocortex, as did generalized spindling. Susceptibility to seizure was reduced in KM rats as a result of protracted and graded increasing camphor administration to match the level of mean EEG spectral density changes characteristic of the Wistar strain. The part which brainstem reticular formation mechanisms may play in raising susceptibility to seizures is discussed, together with the EEG pattern characteristic of this condition.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 171–179, March–April, 1987.     

Brain mechanisms of imagination in solving creative verbal tasks

The brain’s mechanisms of imagination were studied using electroencephalography (EEG) spectral analysis in student actors and student non-actors under three experimental conditions: when they generated coherent stories on the basis of art reproductions (STORY task); listed the details of art reproductions presented (DETAIL task); and performed simple arithmetic calculations while observing a neutral background (COUNT task). Statistical analysis showed that, in α₁ (7.5–10 Hz) and α₂ (10–12.5 Hz) frequency bands, in both groups, execution of the STORY task, in contrast to the DETAIL task, was accompanied by significantly higher spectral power (synchronization) in most of the cortical areas studied; while, the contrasts STORY-COUNT and DETAILS-COUNT, were associated with a decrease in the EEG’s power (desynchronization) in all of the areas studied. Topographic mapping of the EEG’s power showed that, in both groups, maximal differences between the STORY and DETAILS tasks were related to the central parietal area. Maximal differences between the STORY and COUNT tasks, as well as those between the DETAILS and COUNT tasks, were related mainly to the occipital areas. Based on these findings, we consider parietal areas to be stable elements of integrated brain mechanisms underlying verbal creativity in actors and nonactors. Comparing our data with previous studies, we suggest that the parietal areas are involved in the selective inhibition of visual information processing during the involvement of brain structures in the processes of imagination.     

The phenomenon of lowering a seizure readiness level after frequent audiogenic seizures in Krushinskiĭ-Molodkina rats

The spectral analysis of the EEG activity of several brain structures (somatosensory, visual and auditory areas of the cortex, hippocampus, caudate nucleus and central medial thalamic nucleus) in the wakefulness-sleep cycle in Krushinskii--Molodkina strain rats with inherited predisposition to audiogenic seizures using long-lastint reducing of the seizure readiness level revealed in these animals after frequentative audiogenic generalized tonicclonic seizures, was performed. The reducing susceptibility to convulsiogenic sound stimuli in rats correlated with a decrease of the theta-range' waves level and increase of the expression alpha-range waves in the EEG during wakefulness. Probable role of reorganized functions of ascending activating brain systems in origination of the long reduction of susceptibility to the sound after frequentative audiogenic convulsions in rats is discussed.     

Long-term action of camphor on "audio-sensitive" rats: Electrophysiological study and mathematical modeling of properties of neuronal networks

Krushinskii-Molodkina (KM) strain rats genetically predisposed to audiogenic convulsive reaction were given repeated camphor injections in gradually increasing doses (starting at the minimum threshold level required for seizures to occur) over a 4–5 month period. Animals were able to tolerate camphor at doses 3/2–3 times convulsion threshold level without seizure occurring once habituation to the action of this convulsant had been developed. At the same time, the cortical motor zone of strain KM rats acquired properties typical of an epileptic focus: spontaneous epileptiform firing peaks were noted in the background electrical activity of this zone. A decline in the parameter reflecting efficacy of the mechanisms underlying recurrent inhibition emerged in the cortical motor zone of strain KM rats receiving camphor from calculating the parameters of neuronal network from spectra of summated potentials (using the model of a neuronal network). It is suggested that the development of compensatory processes making it possible to avoid generalized seizure following administration of camphor in large doses is associated with intensification of inhibitory caudate function and attenuated hippocampal excitation.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 193–200, March–April, 1990.     

Epileptogenic activity of tripeptide corticotropin-releasing factor fragment (CRF(4-6))

The effects of centrally administered tripeptide fragment CRF(4-6) of corticotropin-releasing factor on convulsive activity in outbred albino rats were investigated. The peptide CRF(4-6) (icv; 6, 30, 150 nmol/head) causes dose-dependent increase in total EEG power in 1-40 Hz frequency range as a reflection of tripeptide-induced various epileptiform EEG signs such as single peaks and spike trains without external convulsion. Higher doses of CRF(4-6) (icv; 150, 225, 300 nmol per animal) induce tonicoclonic seizures. Switching to convulsive activity occurs at CRF(4-6) dose of 150 nmol per animal: injection of this dose leads only to EEG paroxysmal activity under habitual conditions and induces pathological locomotor activation under stressing conditions. Thus, CRF(4-6) similarly to full-length corticotropin-releasing factor induces epileptiform activity in rats.     

Modifications of EEG Related to Directed Perception and Analysis of Olfactory Information in Humans

We recorded EEG in adult volunteers in the course of perception of smells of plant essential oils under conditions of directed attention. It was found that perception of olfactory information, even in the case of mild intensity of the smells inducing no aversive effects, correlates with noticeable changes in the EEG characteristics mostly typical of the reaction of nonspecific EEG activation induced by sensory stimulation and manifested in a decrease in the spectral power, SP, of low-frequency EEG components (6–10 Hz)). In addition, the SP of relatively high-frequency EEG components (11–25 Hz) increased; this effect was most pronounced in the occipital regions of the neocortex. Perception of the smells of essential oils was also accompanied by increases in the coherence of EEG oscillations, most intense in the β2 range (20–25 Hz). Such modifications were maximum in the left temporal/parietal region; this is interpreted as an indication of the special role of these cortical areas in the processes of interaction between the neocortical part of the olfactory analyzer and the respective structures of other analyzer systems. It is hypothesized that such interaction is necessary for the formation of a semantic image of the analyzed stimuli. Neirofiziologiya/Neurophysiology, Vol. 41, No. 1, pp. 70–78, January–February, 2009.     

Features of the stress reaction in rats with genetically-determined emotionality (from EEG indicators)]

The features of the EEG spatial organization in two rat strains, i.e., with expressed emotional reactions (Maudsley reactive, MR) and less reactive (Maudsley nonreactive, MNR) were compared in two stress situations: during exposure to the action of pain (P) (i.p. injection of 0.9% NaCl solution) and during 24-hour water deprivation (D). Multichannel EEG recording (24 derivations) and their multiparametric estimation (840 signs) made it possible to differentiate characteristic features of the EEG spatial organization in rats with initially increased emotional reactions and passive behavioral strategy during exposure to stress. In both stress-inducing conditions, an increase in crosscorrelation and coherence between cortical potentials in parallel with rise of the spectral power in the range of high-frequency theta and its drop in the range of EEG high-frequency band was observed in the MR rats. The MNR rats showed the opposite changes. Different reactivity of the ratio between the coherence and spectral power of potentials was observed in two strains of rats. This index characterizes the level of the information-energy component of the spatial organization of cortical potentials. It is suggested that different character of the EEG changes reflects the features of interhemispheric relations, information-energy processes, and cortical regulation of autonomic processes in the system of adaptive stress reactions at different levels of emotionality and behavioral strategy.     

Changes in spectral coherent characteristics of EEG in the early postpartum period in mothers with anxious and depressed mood

Postpartum EEG spectral and coherence characteristics were estimated in mothers with or without postpartum depressions. In mothers without affective disorders the power of oscillations in the delta, theta, and alpha 1 frequency bands was increased as compared to controls. Intrahemispheric EEG coherence between the left frontal and adjacent derivations in the delta and theta bands and interhemispheric coherence in the central areas was increased and decreased over the remaining cortical surface. These changes led to a significant decrease in EEG asymmetry. It is suggested that during normal postpartum the influence of the limbicodiencephalic and lower brainstem structures on the cortex is augmented and a certain kind of dominanta is formed. In mothers with postpartum depressions the EEG alpha-band power was lower than in the control and normal groups, coherence changes in the delta and theta bands diminished the EEG asymmetry. The insufficiency of limbicodiencephalic influence and impairment of adaptive brainstem reactions are suggested to be responsible for problems in the formation of maternal dominanta, which results in the development of postpartum depressions.     

Individual resistance to factors of monotony reflected in the EEG

Three groups of operators substantially different in their performance quality were examined. Under conditions of monotonous activity, subjects with the highest initial level of activation, minimum EEG total spectral power, and minimum level of EEG coherence in the frontal cortical areas worked most steadily. Under the same conditions, subjects with a rather high spectral power of the theta and beta2 EEG frequency components, highest coherence in the frontal areas, and low coherence in the caudal areas of the cortex worked least steadily. EEG phenomena testify to a rather low level of activation of the frontal cortical areas associated with a facilitation of cortico-subcortical neuronal interactions and an attenuation of the operating neural streams. This results in a decrease in the level of any attention, its involuntary switching, and short-term loss of the control over the current performance.     

Electrographical correlates of adequate and erroneous responses caused by conditioned signals of different functional sign during instrumental conditioning in dogs

Power spectral (in the broad frequency band of 1-225 Hz) of short-term (less than 1 s) EEG reactions were studied in dogs in the course of instrumental food conditioning. These reactions appeared in different cortical areas in response to differentiating signals under conditions of both adequate and erroneous responses. The EEG power of such reactions was several times lower as compared to responses to positive signals, mainly, at the expense of the frequencies in the band of 90-225 Hz (the power of which was higher than that of the traditional band of 1-30 Hz and the gamma band of 30-80 Hz). The frequency composition of EEG reactions accompanying adequate responses was defined, mainly, by discrete subgroups of high-frequency components. During erroneous responses, the discrete structure of the corresponding EEG reactions was broken.     

Changes in the power and coherence of the β<Subscript>2</Subscript> EEG band in subjects performing creative tasks using emotionally significant and emotionally neutral words

Changes in the power and coherence of the β₂ EEG band (18.5–30 Hz) were studied in subjects performing creative tasks under the conditions of emotional induction of different valence and without it. EEGs were recorded in subjects instructed to think up, within a limited time, the largest possible number of original definitions, differing in meaning, of emotionally positive, negative, and neutral nouns using additional words that were selected for them from another or the same semantic field. Significant changes in EEG power and coherence were found in the β₂ band. The performance of the creative task without emotional induction led to a local decrease in β₂ EEG power in the left frontotemporal area and a diffuse decrease in the coherence of the same band in most cortical zones. Emotional induction had a considerably stronger effect on the state of the cortex than the creative tasks used in the study: positive emotional induction caused a generalized increase in the power and coherence of the β₂ EEG band, while negative emotional induction caused a diffuse decrease in the power of this band over the parietal, central, and temporal cortical areas.