[Sleep, emotions and the visceral control].

It is known that sleep is connected with sensory isolation of the brain, inactivation of the consciousness and reorganization of the electrical activity in all cerebral cortical areas. On the other hand, sleep deprivation leads to pathology in visceral organs and finally to the death of animals, while there are no obvious changes in the brain itself. It stays the opened question how the changes in the brain activity during sleep could be con- nected with the visceral health? We proposed that the same brain areas and the same neurons, which in wakefulness process the information coming from the distant and proprioreceptors, switch during sleep to the processing of the interoceptive information. Thus, central nervous system is involved into the regulation of the life support functions of the body during sleep. Results of our experiments supported this hypothesis, explained many observations obtained in somnology and offered the mechanisms of several pathological states connected with sleep. However, at the present level of the visceral sleep theory there were no understanding of the well known link between the emotional states of the organisms and transition from wakefulness to sleep, and sleep quality. In this study the attempt is undertaken to combine the visceral theory of sleep with the need- informational theory ofemotions, proposed by P. Simonov. The visceral theory of sleep proposes that in living organisms there is a constant monitoring of the correspondence of the visceral parameters to the genetically determined values. Mismatch signals evoke the feeling of tiredness and the need of sleep. This sleep need en- ters the competition with the other actual needs of the organism. In according with the theory of P. Simonov emotions connected with a particular need play important role in their ranking for satisfaction. We propose that emotional estimation of the sleep need, based on the visceral signals, is realized in the same brain structures which undertake this estimation for other behavioral needs in wakefulness. During sleep, the same brain structures, involved in estimation of emotions, continue to rank the visceral needs and to define their order for processing in the cortical areas and in the highest level of the visceral integration. In the context of the proposed hypothesis, we discuss the results of the studies devoted to investigation of the link between sleep and emotions.

Visually triggered K-complexes: a study in New Zealand rabbits.

K-complexes are the EEG elements recorded during the state of developing sleep and during slow wave sleep. They are the only EEG components which can be elicited by sensory stimulation during sleep. The peculiarity of New Zealand rabbits to sleep with their eyes open allows the use of visual stimuli to elicit K-complexes. Experiments were performed with three rabbits. For visual stimulation, an elongated screen illuminated by LED flashes was attached to an implant on the animal's skull. The screen covered 20-120° of the visual field of one eye, and moved with the head during animal motion. One-millisecond flashes (15-s interval) were used during daytime in an illuminated room. Flashes elicited evoked responses, which, during the first stages of sleep, were often accompanied by K-complexes. The induced K-complexes were recorded from electrodes located both above visual and somatosensory areas. Evoked responses to visual stimuli were also recorded from both pairs of electrodes, although they were generated exclusively in the visual cortex. Correlation analysis showed that visual evoked responses and K-complexes induced by this stimulation were generated in visual cortex, and passively spread to the electrodes above the somatosensory area. Investigation of the latencies of induced K-complexes revealed two time windows when these complexes could be seen. Within each window there was no correlation between latency and amplitude of K-complexes. There was also no correlation between amplitudes of the visual evoked responses and K-complexes elicited by these responses. We propose that visual stimulation in light sleep temporarily opens a gate for some independent external signals, which evoke activation of the visual cortex, reflected in K-complexes.

[Sleep and pregnancy].

Sleep disturbances are frequent during pregnancy and are currently regarded as one of the most important factors determining pregnancy outcome. Detailed research of sleep features during pregnancy is obviously essential. In the present review recent data concerning changes in sleep structure and regulation in pregnant women and rats - main subjects of experimental sleep research, are given, including surmised mechanisms underlying such changes. The importance of women's sleep integrity preservation during pregnancy for the viability and normal development of the fetus is emphasized and possible ways of pathological influence of sleep disorders during this period are discussed.

[The features of sleep homeostasis in pregnant rats].

To investigate the effects of short-term sleep deprivation on the sleep pattern during pregnancy, cortical and hippocampal EEG and locomotor activity were recorded within 24-hours in a "disk-over-water" paradigm in 18 Wistar rats. Rats were adapted to experimental situation and were able to move across the rotating disk without falling in water. Then a polysomnogram was recorded for 3 sequential days in the control group 1 (n = 12) without disk rotation. On the next day non-pregnant rats (experimental group 1, n = 6) were subjected to the sleep deprivation procedure with a pre-set program of disk rotation from 11:00 to 14:00 during 3 sequential days. Other 6 rats (experimental group 2) were subjected to sleep deprivation on the 5-7th day of pregnancy. EEG and locomotor activity were also constantly recorded during the sleep deprivation procedure. In control group 2 (n = 6, without sleep deprivation), a polysomnogram was recorded on the 5-7th day of pregnancy. As compared to non-pregnant rats, sleep intensity of pregnant rats increased during the first hours after the deprivation, and a considerable rebound of REM sleep took place. Sleep pattern during the off-light 12 hours remained unchanged. The results suggest that homeostatic compensation of sleep deprivation effects in rats on the first week of pregnancy is more efficient than in control non-pregnant animals.

[The history of observations and some methodological features of the studies on local sleep]. / K istorii nablyudeniya i nekotorym metodicheskim osobennostyam issledovaniya proyavlenii lokal'nogo sna.

The phenomenon of local sleep, a concept that has come into somnology relatively recently, has been attracting more and more attention of researchers. Under this name, two groups of phenomena are considered. The first is the appearance in different parts of the cerebral cortex of different EEG patterns during general sleep. The second is the disconnection of certain cortical areas from the processing of extero- or proprioceptive signals and their transition to spiking and slow wave electrical activity, which is typical for sleep, while awake. The authors believe that it is the second phenomenon that can be called real local sleep. The appearance of local cortical sleep is inseparably linked with the occurrence of local wakefulness. It can be expected that the occurrence of local sleep will have detrimental consequences for behavior in urgent and complicated situations, while local wakefulness can adversely affect the visceral health of the body. A possible way of early detection of the local sleep development is proposed. In conclusion, some methodological problems on the way of electrophysiological studies of the local aspects of sleep and wakefulness are considered.

[Efficiency of the "disk-over-water" method without feedback for sleep deprivation in rats].

The "disk-over-water" method, where animals are awakened by disk rotation triggered by sleep EEG signals, was efficiently used in many studies involving sleep deprivation. Recently, the modification of this method has been developed where, during the period of deprivation, the disk was rotated in accordance with a pre-set program (the "disk-over-water" method without feedback). We considered this modification as a potentially promising one for investigation of relationship between maternal sleep and litter development. However, none of these methods has been used in experiments on female rats, and efficiency of the method without feedback has never been tested using electrophysiological estimation of sleep-wake states either. Performing these tasks was the goal of the present study. Cortical EEG, hippocampal theta-activity and locomotor activity were recorded in 14 female Wistar rats underwent sleep deprivation in the "disk-over-water" setup without feedback. Three days long during the deprivation periods from 11:00 to 14:00 the disk was rotated for 8 s with 15 s intervals. REM sleep was totally eliminated during these periods, and amounts of slow wave sleep did not exceed 10% of 3 h. The results were identical both for pregnant and non-pregnant rats. The rate of sleep reduction during deprivation periods in our experimental conditions did not differ from that in the original system with the feedback. Thus the simplified "disk-over-water" method without feedback can be used in the studies involving relatively short sleep deprivation periods.

[On the mechanism of therapeutic effects of electrostimulation. Interpretations and predictions based on the results of sleep studies]. / K mekhanizmu terapevticheskogo éffekta élektrostimuliatsii. Interpretatsii i predskazaniia, osnovannye na rezul'tatakh issledovanii sna.

Based on the studies of the transition from wakefulness to sleep, we propose that therapeutic effect of various types of electrical stimulations can be related to growing sleepiness promoted by the stimulation, and to the improvement of sleep quality resulted from this procedure. Namely, improved sleep but not the stimulation itself will cause the therapeutic effect. The authors also discuss the probable mechanisms of the anticonvulsive effects of the vagus nerve stimulation and suggest that this effect could be caused by the changes in rhythmical activity of the visceral organs as a result of stimulation. Changes in these frequencies will shift them out of the resonance range of the cortical neuronal circuits, towards which propagation of these visceral signals is opened during sleep.

[Sleep patterns and the efficiency of the gentle methods of sleep deprivation in rats at different stages of pregnancy: behavioral study].

In Wistar rats, pregnant or not pregnant, sleep-wakefulness parameters were registered for 2 days from 10:00 till 14:00. Later, these rats were subjected to 3-hour (11:00-14:00) daily sleep deprivation (SD) during 3 consecutive days. To prevent sleep, the following manipulations were used: acoustic stimulation from moving of the food pellets, opening or horizontal rotation of the cage and gentle handling. Control pregnant or not pregnant rats were placed in individual cages in the same room, but their sleep was not disturbed. On average, not pregnant rats spent about 65% of the time in sleep. Sleep episodes were mostly short (less than 1 min) or medium (1-15 min). After the beginning and with advance of pregnancy, the amount, deepness and duration of sleep episodes increased. With the methods of SD used, not pregnant rats did not sleep almost at all during the SD session. In pregnant rats, the quantity and intensity of stimuli used for SD increased as compared to control, which was indicatives of the growth of "sleep pressure" during pregnancy.

[Progress of sleep studies in the age of electrophysiology. The visceral theory of sleep]. / Progress izucheniia sna v épokhu élektrofiziologii. Vistseral'naia teoriia sna.

Electrophysiological methods of studying the nervous system have opened up new opportunities for investigations of sleep. Striking changes in the pattern of EEG during the transition from wakefulness to sleep made it's recording a mandatory element of any somnological research. It was also found that the frequency of neuronal firing in the cerebral cortex during sleep does not decrease, but can significantly exceed the average level of the cortical activity during wakefulness. But it remained the main mystery of sleep, what was associated with this high activity of cortical neurons at a time when the thresholds of sensory perception raised and the propagation of signals from the outside world and from the own body towards the cerebral cortex were almost blocked. The resolution of this paradoxical situation was suggested by the visceral theory of sleep. This theory was based on the assumption that during sleep interoceptive afferentation from all visceral systems of the body arrives for analysis into the cerebral cortex. This article offers an overview of the studies performed for direct experimental verification of non-trivial predictions of this theory.

[Long and difficult way towards the understanding of sleep function. Period before the age of electrophysiology]. / Dolgii i trudnyi put' k ponimaniiu naznacheniia sna. Étap do épokhi poiavleniia élektrofiziologii.

It was proposed that historical analysis of ideas concerning the function of sleep will help to evaluate the tendencies in this field of science and will show the probable direction for further approach to understanding of this problem. We reviewed ideas of Ivan Pavlov and his Russian forerunners (Ivan Tarkhanoff and Maria Manaceine) and followers (Nikolay Rozjanskiy and Konstantin Bykov) on the functional role of sleep. This analysis led to the conclusion that state of sleep have been connected with realization of such functional operations, which have not been considered in the past and are not under consideration in the present neuroscience. Thus, one can expect that real understanding of sleep function will come only with new neurophysiologic paradigm.

[Prenatal experience and postnatal development of the rat hippocampus: sleep deprivation of pregnant rats].

The effects of sleep deprivation in pregnancy on the development of hippocampal function of the offspring have been investigated. For this purpose we compared electrophysiological characteristics in the hippocampal slices of 15-20-old-day rats of the control and two experimental groups. In the first experimental group the pups were taken from mother for weighting three times during the first postnatal week and then weekly. Another experimental group was brought up without handling. We found that CA1 population spikes developed to significantly less amplitude in experimental groups of rat pups. This phenomenon was observed at higher intensity of monosynaptic activation, although near-threshold stimuli didn't reveal any differences among groups. However, under paired-pulse stimulation (70 ms inter-pulse interval) small amplitudes in the hippocampal slices of experimental animals could facilitate up to control value, and second in pair responses didn't differ from corresponding control. Our data doesn't confirm the hypothesis about decreased connectivity in the hippocampus of experimental rats, but the efficacy of CA3-CA1 inputs seems to be lower. Besides excitatory transmission, the effectiveness of inhibition of paired-pulse facilitation at 15 ms inter-pulse interval was also significantly decreased. The observed effects of prenatal influences seem to develop under postnatal experience. We observed significant trend to more pronounced modifications upon age especially in the case of early handling and testing.

Elaboration of conditioned alimentary reflexes having different probabilities of reinforcement in rats with hippocampal lesions.

A motor alimentary conditioned reflex was elaborated in hippocampectomized and intact albino rats. Food reinforcement followed 100 percent, 50 percent, 33 percent or 25 percent of conditional stimulus presentations (click from a rotating food box). No differences were found in the rate of conditioned alimentary reflex elaboration between the hippocampectomized and control rats at 100 percent and 50 percent reinforcement, although the time-courses of formation of the conditioned reflex connection differed substantially. With low reinforcement probabilities (33 percent and 25 percent) the operated rats, unlike the intact ones, exhibited no adequate responses throughout the 10 experimental days. The results obtained corroborate an earlier suggestion that the hippocampus is involved in the organization of behavior the reinforcement probability of which is unknown or relatively low.

Comparative psychological approach to the analysis of the functions of the hippocampus.

As compared with dogs, the development of conditioned reflex switching-over of heterogeneous conditioned reflexes in intact rats is often accompanied by the development of reactions of the neurotic type. Experiments involving injury of the hippocampus (in rats) and the recording of electrical activity (in dogs) showed that this structure participates in the formation of conditioned reflex switching-over of instrumental reflexes. Following the injury to the hippocampus, the rats successfully formed the switch-over. The switch-over signal altered the electrical activity of the hippocampus in the dogs. Consequently, the hippocampus in both species of animals belongs to the system of structures which participate in the formation of conditioned reflex switching-over. Hippocampectomized rats were not capable of developing an alimentary conditioned reflex at the 30% level of reinforcement. The highest values of the frequency of the hippocampal theta rhythm were obtained in the dogs at just this level of probability of reinforcement. These data indicate that the assurance of reactions to signals with a low probability of reinforcement is an important function of the hippocampus in various species of animals.

Sensory information--the major factor of ontogeny.

On the basis of their own data authors postulate that the increase in sensory input during early ontogeny results in a delay in the development of the sensory systems formed earlier. In connection with this, the sensory basis of behavioral patterns becomes ineffective, causing their reorganization and the appearance of new forms of behavior. Limitation of sensory input during during the critical periods of development stimulates the accelerated manifestation of behavioral patterns. However, this acceleration also has long-lasting negative effects - alterations in the process of learning and memory in adult animals.

[Switching-over of homogeneous (alimentary) conditioned reflexes in rats following simultaneous lesions of the hippocampus and amygdala]. / Perekliuchenie odnorodnykh (pishchevykh) uslovnykh refleksov u krys posle odnovremennogo povrezhdeniia gippokampa i mindaliny.

Conditioned switching-over of homogeneous (alimentary) conditioned reflexes was elaborated in intact rats and in rats with simultaneously lesioned hippocampus and amygdala; time of the day served as switching stimulus. The operated rats showed higher values of intersignal and conditioned motor activity and easier conditioned switching-over than intact animals. It is suggested that the lesion of the amygdala enhances the effect of accelerated elaboration of the switching-over observed in animals with lesioned hippocampus, due to the elimination of competing (non-alimentary) motivations.

[Formation of alimentary conditioned reflexes with probable reinforcement in rats with frontal cortex injuries]. / Formirovanie pishchevogo uslovnogo refleksa pri veroiatnostnom podkreplenii u krys s povrezhdeniem frontal'noi kory.

Alimentary conditioned response to the sound of turning of the feeding-rack reinforced in 33 and 25 per cent of cases was formed faster in rats with frontal cortical lesion than in intact animals. The results obtained permit to suppose that during integrative brain activity the frontal areas of the cerebral cortex participate in organization of behavior with a high probability of reinforcement.

[Morphologic analysis of the consequences of simultaneous lesioning of the hippocampus and amygdala in the rat]. / Morfologicheskii analiz posledstvii odnovremennogo povrezhdeniia gippokampa i mindaliny u krys.

The comparison of damage localization in the region of the hippocampus and amygdala with changes of behaviour components in operated rats revealed an increase of alimentary excitability, motor and intersignal activity following damage of the dorsal part of the hippocampus and destruction of all the parts of amygdala, whereas the elaboration of transswitching of heterogeneous (alimentary and defensive) conditioned reflexes became difficult. If the hippocampus was fully destroyed and amygdala damage was confined to its corticomedial part, then the motor activity was enhanced only in some animals and alimentary excitability and intersignal activity, as a rule, did not differ from those in the intact rats. The elaboration of transswitching of heterogeneous conditioned reflexes in this case was facilitated.

[The influence of the emotional state of the child on the parameters of its verbal response]. / Vliianie émotsional'nogo sostoianiia rebenka na parametry rechevogo otveta.

The method of determination of human emotional state by speech was applied to the analysis of verbal expressions of 22 children during the play "make-up the square". Parameters of the verbal response--F0 (fundamental frequency) and n(0) (evaluation of the frequency of the first formant) changed to the greatest extent under the influence of emotional reactions which appeared in children during the play. Depending on the terms of the play different changes of these parameters took place in different children: in some cases significant increase of values was observed as compared with the background ones, in other cases--their significant decrease.

[A comparative neuropsychological approach to the analysis of hippocampal functions]. / Sravnitel'no-neiropsikhologicheskii podkhod k analizu funktsii gippokampa.

Formation of conditioned switching-over of heterogeneous instrumental reflexes in dogs was more successful than in rats, which testifies about significant differences of the functional organization of analytical-synthetic brain activity in rodents and predatory animals. Experiments with lesion of the hippocampus (in rats) and the records of its electrical activity (in dogs) allowed to conclude that the hippocampus of the both types of animals belongs to the system of structures, participating in the formation of conditioned switching-over. The data, obtained in the process of elaboration of the switching-over and probabilistic reinforcement of the alimentary conditioned stimulus, testify that providing for the reactions to signals with low probability of reinforcement in different species of animals is one of the functions of the hippocampus.

[Effect of hippocampal damage on emotional stress in rats]. / Vliianie povrezhdeniia gippokampa na émotsional'noe napriazhenie u krys.

Motor reactions and ECGs were recorded in rats with lesioned hippocampus and in intact animals during elaboration of conditioned switching over of heterogeneous conditioned reflexes (alimentary and defensive). In hippocampectomized rats, in contrast to intact ones, the formation of this complex conditioned activity is not accompanied by pronounced vegetative reactions and changes in the ECG. The data obtained point to an active involvement of the hippocampus in formation of emotional stress and confirm the concept of the hippocampus as a brain structure, providing for responses to signals of events with low probability.