Effect of unilateral spreading cortical depression on intraspecies aggression and sociability of isolated mice

It has been shown that aggressive forms of behaviour are controlled preferentially by the left hemisphere and sociability by the right one. Consequently, the opposite poles of the continuum "aggression-sociability" have different lateralization. Interconnection between functional interhemispheric asymmetry and aggression degree has been revealed: in high-aggressive mice the differences in the effect of left and right hemispheres inactivation are expressed stronger as compared to low-aggressive and nonaggressive animals.     

Characteristics of the intraspecies interaction of rats with differing zoosocial experience

It has been found that among white outbred rats with different experience of intraspecies contact four types of reaction to the partner are singled out in the "stranger-resident" test: active, neutral passive, highly-aggressive. Belonging to one or another type is determined by the level and correlation of aggression and intraspecies sociability. Among animals isolated in an adult age, all four types of reaction to the partner are represented while in rats kept in isolation since 13--14th day of life only one type is presented--the active one. For animals of the control group the first three types of reaction are typical. It is revealed that only "late" isolation leads to a pathological increase of aggressivity in a part of the animals; an increase of aggression in "early" isolants may be considered as a consequence of sharp rise of intraspecies sociability. Conclusion is made about principal difference in mechanisms of aggression increase in "early" and "late" isolants.     

Pharmacoethological analysis of the action of beta-carbolines

The ethological spectrum of four beta-carbolines was studied for intraspecific aggression, sociability integration and individual behavior. It was established that beta-carboline-3-carboxyethyl ether given at subconvulsant doses increases aggression, lowers sociability as a diazepam antagonist. Diazepam reduces aggression and increases sociability. It is suggested that benzodiazepine receptors are involved in the integration of interspecific sociability and aggressive behavior of the "attack" type. Aggression of the defence type has no inhibitory beta-carboline control (1-methyl-6-methoxy-dihydro-beta-carboline). The differences in the ethological spectra of beta-carbolines have been demonstrated.     

Word retrieval learning modulates right frontal cortex in patients with left frontal damage

Previous studies have suggested that recovery or compensation of language function after a lesion in the left hemisphere may depend on mechanisms in the right hemisphere. However, a direct relationship between performance and right hemisphere activity has not been established. Here, we show that patients with left frontal lesions and partially recovered aphasia learn, at a normal rate, a novel word retrieval task that requires the damaged cortex. Verbal learning is accompanied by specific response decrements in right frontal and right occipital cortex, strongly supporting the compensatory role of the right hemisphere. Furthermore, responses in left occipital cortex are abnormal and not modulated by practice. These findings indicate that frontal cortex is a source of top-down signals during learning.     

Levels of consciousness and levels of activation

In the paper Pavlov's idea is used about "the bright spot of consciousness" as a zone of increased excitability which moves over the cerebral cortex. Zone of increased activation is revealed migrating from the frontal parts of the left hemisphere to the occipital parts of the right hemisphere. By means of various methods (record of amplitude and latency of the visual evoked responses, frequency and amplitude of the dominant rhythm, spectral-coherent analysis of the electroencephalogram) the activation of focus in the cerebral cortex was singled out, which moved, depending on the novelty, complication and degree of automatization of the task, from the frontal parts of the left hemisphere to the occipital parts of the right hemisphere. A parallel is drawn between Pavlov's hypothesis on the focus of consciousness as foci of increased brain activity, and revealed foci of activation. The conclusion is made about fluctuations of consciousness level as a factor which is in the basis of activation focus migration.     

Pharmacoethological analysis of the effects of thyroliberin and melanostatin in a model of anxious-defensive behavior in mice

Psychotropic properties of thyroliberin and melanostatin were studied on the model of timid-defensive behaviour of mice. Oligopeptides increased defensive behaviour and timidity, and decreased intraspecies sociability. GABA deficiency and dopaminergic system blockade increased timid-defensive behaviour of mice. Mobilizing activity of peptides on the agonistic behaviour (aggression and defense) may be explained by their anxiogenic properties.     

Spatial attention and neglect: parietal, frontal and cingulate contributions to the mental representation and attentional targeting of salient extrapersonal events.

The syndrome of contralesional neglect reflects a lateralized disruption of spatial attention. In the human, the left hemisphere shifts attention predominantly in the contralateral hemispace and in a contraversive direction whereas the right hemisphere distributes attention more evenly, in both hemispaces and both directions. As a consequence of this asymmetry, severe contralesional neglect occurs almost exclusively after right hemisphere lesions. Patients with left neglect experience a loss of salience in the mental representation and conscious perception of the left side and display a reluctance to direct orientating and exploratory behaviours to the left. Neglect is distributed according to egocentric, allocentric, world-centred, and object-centred frames of reference. Neglected events can continue to exert an implicit influence on behaviour, indicating that the attentional filtering occurs at the level of an internalized representation rather than at the level of peripheral sensory input. The unilateral neglect syndrome is caused by a dysfunction of a large-scale neurocognitive network, the cortical epicentres of which are located in posterior parietal cortex, the frontal eye fields, and the cingulate gyrus. This network coordinates all aspects of spatial attention, regardless of the modality of input or output. It helps to compile a mental representation of extrapersonal events in terms of their motivational salience, and to generate 'kinetic strategies' so that the attentional focus can shift from one target to another.     

Effects of sex factors and hemispheric localization on the involvement of serotonin from the frontal cortex, striatum, and nucleus accumbens into the processing of novel and repeatedly presented information in rats

The effects of novel or relevant (a single exposure to experimental chamber) and irrelevant (20 exposures to experimental chamber) stimuli on the levels of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the frontal cortex, striatum, and nucleus accumbens in the left and right hemispheres were studied in male and female rats. It was found that 5-HT and 5-HIAA contents in the frontal cortex changed in response to neither relevant nor irrelevant stimuli. However, there were hemispheric difference in 5-HT and 5-HIAA in the frontal cortex of intact animals. The level of 5-HT in males and the level of 5-HIAA in females were higher in the left frontal cortex. In females, the level of 5-HIAA in the left striatum decreased in response to the novel stimulus. Sex differences in: a) 5-HT metabolism (increase in the level of 5-HIAA in males and increase in 5-HT in females) and b) lateralization (the striatal 5-HT metabolism in males changed bilaterally and only in the left hemisphere in females) were observed in reactions to irrelevant stimuli. Both in male and female rats, serotonin content in the nucleus accumbens changed only in response to the irrelevant stimuli. The 5-HT level increased in the left and right hemispheres independently of sex, but hemispheric difference was revealed only in females, in which the serotonin level was higher in the left nucleus accumbens. It is concluded that serotonergic neurotransmitter mechanisms are involved in hemispheric and sex differences in selective attention.     

The locked-in patient and the characteristics of the electrical activity of his brain

"Locked-in" state differs from the known states characterized by the motor activity blockade, preservation of conscience of speech contact, despite the fact that connection with outer world during this state is limited only by vertical movements of eyes and eyelids in response to speech signals. Three "locked-in" men were studied at different stages of development of this state. Spectral-coherent analysis of the EEG was conducted. The most typical for the developed state of the "locked-in" man is a uniform change of the intercentral EEG relations. In the motor areas of the cortex alpha-activity and its links are not formed (coherence in alpha-range is zero) while high and low frequencies are coherent. In the visual areas, in contrast, the alpha-rhythm is coherent. Distinct interhemispheric asymmetry of coherent connections appears. In the right hemisphere a decrease of coherence level is sharp and even, in the left one--in occipito-temporal parts the level remains close to norm, while in the frontal parts of the cortex it decreases.     

The neural basis of hyperlexic reading: an FMRI case study

Children with autism spectrum disorders in very rare cases display surprisingly advanced "hyperlexic" reading skills. Using functional magnetic resonance imaging (fMRI), we studied the neural basis of this precocious reading ability in a 9-year-old hyperlexic boy who reads 6 years in advance of his age. During covert reading, he demonstrated greater activity in the left inferior frontal and superior temporal cortices than both chronological age- and reading age-matched controls. Activity in the right inferior temporal sulcus was greater when compared to reading age-matched controls. These findings suggest that precocious reading is brought about by simultaneously drawing on both left hemisphere phonological and right hemisphere visual systems, reconciling the two prevailing, but seemingly contradictory, single hemisphere theories of hyperlexia. Hyperlexic reading is therefore associated with hyperactivation of the left superior temporal cortex, much in the same way as developmental dyslexia is associated with hypoactivation of this area.     

Interference with ritualized threat behaviour in Cichlasoma nigrofasciatum

According to ethological theory, ritualized threat behaviour functions to prevent overt aggression. This prediction was tested in twenty-three pairs of male Cichalasoma nigrofasciatum. Pairs prevented from giving frontal displays by surgically restrained gill covers showed significantly less mouth fighting than sham operates. Pairs prevented from giving frontals and impaired in delivering tail beats because of separated caudal-fin rays showed intermediate aggressive behaviour. Experimental animals in both groups fought and frequently became dominant when paired with sham operates. It was concluded that threat behaviour in C. nigrofasciatum increases subsequent aggressive behaviours both quantitatively and qualitatively. It is suggested that ethological theory has identified the effects of ritualized aggression as a complex behavioural sequence ending in submissive behaviour with that of its first phase alone.     

Functional asymmetry of electric processes in the rabbit brain cortex at formation of the hunger dominant

The motivational condition of hunger and formation of the hunger dominant after daily food deprivation was studied in the conditions of chronic experiments on rabbits. It was shown, that the hunger condition was accompanied by left sided interhemispher asymmetry on indicators of spectral capacity of EEG frontal and right-hand asymmetry sensorimotor areas of the cortex. A hunger dominant was accompanied by falling of spectral capacity of EEG of areas of both hemispheres. The condition of hunger and a hunger dominant were characterized by right-hand asymmetry on average level of EEG coherence of frontal and sensorimotor areas. At transition of a condition of hunger in a hunger dominant there was an average level of EEG coherence decrease in areas of the right hemisphere. Electric processes of the cortex of the brain at a motivational condition of hunger and a hunger dominant were different.     

EEG reactions during creative activity

Evoked activity in response to light was recorded in students performing a verbal creative task. The changes in the amplitude of the N200 negative component of evoked potentials were analyzed. The amplitude of the N200 component was significantly increased in the frontal and anterior frontal areas of the left hemisphere, which indicated increased activity in the cortical structures involved in divergent thinking. The amplitude of the N200 component was increased in the temporo-parieto-occipital area of the right hemisphere, which indicated that the posterior associative region of the right hemisphere was also involved in the creative activity. The data obtained suggest that the frontal and temporo-parieto-occipital areas of the cerebral cortex actively participate in the performance of a creative test with distinct elements of complexity.     

The structure of dependent relationship between neurons in the sensorimotor cortex of the left and right hemisphere in rabbits during immobilizing catatonia

Relations between activities of neurons simultaneously recorded in the left and right sensorimotor brain cortices of rabbits were analyzed in a series of experiments before the induction of the immobilization state ("animal hypnosis"), in the state of immobilization, and after its termination. The total baseline percent of significant correlations between activities of neighboring (within 50 microns) neurons in the left hemisphere was significantly lower than in the right hemisphere. This characteristic of the left hemisphere changed neither in the immobilization state nor after its termination. In the right-hemisphere cortex, the total percent of correlations between neighboring neurons significantly decreased during immobilization and returned to the baseline level after the termination of this state. In contrast, percent of correlations between the activities of remote (within 500 microns) neurons in the right-hemisphere did not change during immobilization, whereas in the left cortex it changed significantly and reached its baseline level after the normalization of rabbit's state. Further analysis showed that the revealed cortical interhemispheric asymmetry is underlain by asymmetric activities of individual neurons and small neuronal populations. Thus, for example, changes in the structure of interneuronal correlations in cortical microareas of the left and macroareas of the right hemispheres could be of different directions, whereas correlated activities in microareas of the right and macroareas of the left-hemispheres could change synergetically. In other words, asymmetry was revealed at different levels of neuronal integration (neuronal pairs, micro- or macrogroups of neurons). This finding testifies to a mosaic character of neuronal activity, which finally results in the general functional asymmetry during the "animal hypnosis". Certain changes in the structure of functional relations between neurons of the sensorimotor cortex that developed in the state of "animal hypnosis" persisted and even augmented after the termination of this state.     

Influence of aggressive computer games on the brain cortex activity level in adolescents

Dynamic changes in the activities of different areas of the brain cortex were studied in order to determine cortical structures responsible for playing aggressive computer games, with the degree of initial aggression of the adolescent subjects taken into account. Changes in anxiety and aggression produced by aggressive computer games were found to depend on the initial level of aggression of the subjects. In adolescents with a high baseline level of aggression, the amplitude of the N200 component increased in the frontal and decreased in the temporal areas of the cortex, whereas, in adolescents with a low baseline aggression level, N200 decreased in the frontal and increased in the temporal cortical areas.     

Hemispheric specialization in dogs for processing different acoustic stimuli

Considerable experimental evidence shows that functional cerebral asymmetries are widespread in animals. Activity of the right cerebral hemisphere has been associated with responses to novel stimuli and the expression of intense emotions, such as aggression, escape behaviour and fear. The left hemisphere uses learned patterns and responds to familiar stimuli. Although such lateralization has been studied mainly for visual responses, there is evidence in primates that auditory perception is lateralized and that vocal communication depends on differential processing by the hemispheres. The aim of the present work was to investigate whether dogs use different hemispheres to process different acoustic stimuli by presenting them with playbacks of a thunderstorm and their species-typical vocalizations. The results revealed that dogs usually process their species-typical vocalizations using the left hemisphere and the thunderstorm sounds using the right hemisphere. Nevertheless, conspecific vocalizations are not always processed by the left hemisphere, since the right hemisphere is used for processing vocalizations when they elicit intense emotion, including fear. These findings suggest that the specialisation of the left hemisphere for intraspecific communication is more ancient that previously thought, and so is specialisation of the right hemisphere for intense emotions.     

Functional Asymmetry of the Brain and Ignoring of the Environment

Manifestations of functional asymmetry of human cerebral cortex at spatial orientation in the visual and auditory systems are considered. Disorder of the right hemisphere activity leads to two main interrelated disorders: ignoring of a portion of the extrapersonal space on the left and compression of this space on the right. The revealed disorders are considered as a result of suppression of activity of brain structures (first of all, of the parietal area of the right cortex) that form body scheme (the reference level at the spatial orientation). The suggestion is made about causes of ignoring of the external sensory space in disturbances of the right parietal cortex area. Role of the right hemisphere in other possible forms of ignoring of the external space is considered.     

Study of the role of the right and left orbitofrontal cortex in compensatory cerebral reactions after acute brainstem damage

Significance of the right and left orbitofrontal cortex (OFC) in recovery after acute brainstem lesion (at the level of n. Deiters) was investigated using rat model of complex brainstem-orbitofrontal cerebral damage. It was found that the right-side lesion of the OFC combined with isolated brainstem damage resulted in aggravation of the animal condition and highly probable lethal outcome within the first two weeks after surgery (because of the brain circulation disorder of hemorrhagic type). It may be associated with sympathetic activation. It is suggested that a certain "stimulation" of the left OFC (as the effect of its incomplete destruction) involves a parasympathetic compensatory reaction that allows animals with a severe brainstem pathology to survive. It is shown that, with the general nonspecific tendency to postoperative increase in emotionality, the greatest shifts in the emotional sphere take place under conditions of a combined damage of the brainstem and left OFC.     

Group Independent Component Analysis and Functional MRI Examination of Changes in Language Areas Associated with Brain Tumors at Different Locations

Object

This study investigates the effect of tumor location on alterations of language network by brain tumors at different locations using blood oxygenation level dependent (BOLD) fMRI and group independent component analysis (ICA).

Subjects and Methods

BOLD fMRI data were obtained from 43 right handed brain tumor patients. Presurgical mapping of language areas was performed on all 43 patients with a picture naming task. All data were retrospectively analyzed using group ICA. Patents were divided into three groups based on tumor locations, i.e., left frontal region, left temporal region or right hemisphere. Laterality index (LI) was used to assess language lateralization in each group.

Results

The results from BOLD fMRI and ICA revealed the different language activation patterns in patients with brain tumors located in different brain regions. Language areas, such as Broca’s and Wernicke’s areas, were intact in patients with tumors in the right hemisphere. Significant functional changes were observed in patients with tumor in the left frontal and temporal areas. More specifically, the tumors in the left frontal region affect both Broca’s and Wernicke’s areas, while tumors in the left temporal lobe affect mainly Wernicke’s area. The compensated activation increase was observed in the right frontal areas in patients with left hemisphere tumors.

Conclusion

Group ICA provides a model free alternative approach for mapping functional networks in brain tumor patients. Altered language activation by different tumor locations suggested reorganization of language functions in brain tumor patients and may help better understanding of the language plasticity.     

Correlated activity of neurons in the sensorimotor cortex of rabbits in the state of defensive dominanta and "animal hypnosis"

A hidden excitation focus (dominanta focus) was produced in the rabbit's CNS by threshold electrical stimulation of the left forelimb with the frequency of 0.5 Hz. As a rule, after the formation of the focus, pairs of neurons with prevailing two-second rhythm in their correlated activity were revealed both in the left and right sensorimotor cortices (with equal probabilities 29.3 and 32.4%, respectively). After "animal hypnosis" induction, the total percent of neuronal pairs with the prevalent dominanta-induced rhythm decreased significantly only in the right hemisphere (21%). After the termination of the "animal hypnosis" state, percent of neuronal pairs in the right cortex with prevailing two-second rhythm significantly increasead if the neurons in a pair were neighboring and decreased if they were remote from each other. Similar changes after the hypnotization were not found in the left cortex. Analysis of correlated activity of neuronal pairs with regard to amplitude characteristics showed that for both the right and left hemispheres, the prevalence of the two-second rhythm was more frequently observed in crosscorrelation histograms constructed regarding discharges of neurons with the lowest spike amplitude (in the right hemisphere) or the lowest and mean amplitudes (in the left hemisphere) selected from multiunit records.