Changes in Interhemispheric Interaction at the Course Pharmacotherapy of Psychoses

Using graphic tests, preference of space parts and peculiarities of space depth reflection were studied in drawings of in-patients with depression, maniacal state, and paranoid schizophrenia. The examination was performed in the process of the course treatment with neuroleptics and antidepressants. Two opposite patterns of raster filling and space reflection were revealed in the drawings: (1) preference of the left part of space, reflection of objects in the nearest part of space; (2) preference of the right part of space, reflection of the distant part of space. It is suggested that a shift of interhemispheric activation balance towards the right hemisphere occurs in the depressive state, whereas a shift to the left is observed in the maniacal state and paranoid schizophrenia. Psychotropic drugs produce a lateralization effect on cerebral hemispheres: antidepressant amitryptyline leads to a decrease of pathological activation of the right hemisphere, while neuroleptic haloperidol, of pathologic activation of the left hemisphere.     

Functional asymmerty of the brain and emotions

Different kinds of emotional phenomena are related in a different way with the workings of the left and right hemispheres of the brain. Emotional reactions (phasic emotions), which appear on the basis of a cognitive loading (mental representation, recognition, play, prognostication, watching movies, reading of emotionally colored texts or separate words and so on) and which are tested with the help of electrophysiological methods, activate different regions of the left and right hemispheres of the brain depending on the complexity and novelty of emotiogenic situations as well as on the degree of subject's emotional tension. The tonic emotions individual background-mood, on which depends the emotional estimation (negative of positive) of the presented stimuli or events, are determined mostly by a prolonged, relatively stable, tonic activation of each hemisphere connected with subjects' individual characteristics. The predominance of the left hemisphere activity creates positive emotional background, whereas the predominance of the right hemisphere creates negative background.     

Hemispheric participation in the shaping of spatial-motor asymmetry in visual recognition in rats

Asymmetry of movement direction was found in Wistar rats at establishing of motor alimentary conditioned reflex to simultaneously presented visual stimuli. In the course of learning the asymmetry weakened on the whole, but some individuals retained right- or left side preference. The analysis of asymmetry change before and after unilateral cortical inactivation revealed a special role of right hemisphere influences for the formation of right-side preference and of the left hemisphere--for the choice of the left direction. The lack of asymmetry was observed at the presence of the influences from the left hemisphere cortex depressing ipsilateral nigro-striate system and activating the contralateral one. Influences of the cortex of both hemispheres reduce the absolute value of the asymmetry coefficient; the left hemisphere has a special significance for manifestation of temporal asymmetry parameters. Photic interference is a factor modulating the asymmetry. It reduces the right hemisphere activity more than that of the left one; it intensifies right hemisphere influences, contributes to the involvement of the transcallosal conduction channel in the formation of spatial-motor asymmetry.     

Sex Differences and Activity of the Left and Right Brain Hemispheres

The problem is reviewed of sex differences and the brain organization of the visual-spatial and verbal-cognitive functions both in adults and in the 5–15-year old children. Characteristic of men are the integral strategy of the face image recognition, specialization of the right hemisphere for visual-spatial functions, and the tonic inhibitory effect of the right hemisphere on the left one. Typical of women are the fragmented type of the image recognition, the equality of the brain hemispheres functions at the unfamiliar face recognition, and predominance of the left hemisphere by accuracy of the object localization in the visual field. It is possible that the general strategy of the recognition in women is not realized due to the right hemisphere submitted to the interfering effect of the left hemisphere. Analysis of sex differences in distribution of verbal functions shows that the capability for the verbal learning at the age of 5 years and older is higher in girls than in boys. Such capability seems to be accounted for by the superiority of the left hemisphere in girls in this type of its activity and by its earlier development and maturation. The phenomenon of semantic paralexia appearing more often in boys is accounted for by inclusion of lexical-semantic fields of the right hemisphere symmetric areas in the verbal-cognitive activity There are reasons to believe that the higher capability in girls for the verbal learning is mainly due to processes of the auditory-verbal integration within the limits of the left hemisphere, whereas this verbal ability in boys depends on the relative predominance of the interhemispheric connections.     

The psychophysiological testing of temperament]

A comparison was carried out of the dynamics of the activation focus of the human cerebral cortex with the data of psychological testing by the ergic parameter of the "Questionnaire for estimation of temperament structure". It is shown that the right hemisphere in the subjects conditionally attributed to the sting type ("highergice") is much more involved involving verbal tasks than in "week" types. In subjects conditionally attributed to the "week" type, at fulfillment of verbal tasks inert predominance of the left hemisphere activation is noted.     

Lateralization of perception of short time intervals and cortical evoked activity in man

Recognition of short time intervals (10, 60, and 180 ms) between visual stimuli presented to the left or right hemisphere was studied in adult healthy people. The interval of 180 ms is recognized better than that of 10 or 60 ms. Learning with repeated tests with 180 ms intervals proceeds better than that with short intervals. The predominance of the left hemisphere has been revealed only for perception of 10 ms interval. The other time intervals asymmetry is not observed. It is suggested that the left hemisphere is predominant in estimation of short (less than 60 ms) time intervals. In formation of time nervous model a significant role is played by local activation of the cortical zone where the standard stimulus is addressed.     

Event-related synchronization and desynchronization of EEG during appraisal of threatening and pleasant visual stimuli in high anxious subjects

The 62-channel EEG was recorded while low (LA, n = 18) and high (HA, n = 18) trait-anxious subjects viewed sequentially presented neutral, threatening and pleasant IAPS stimuli. Event-related desynchronization (ERD) and synchronization (ERS) were studied in the delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma frequency bands. Between-group differences, related to stimulus emotionality, were linked to theta1 and theta2 bands. In the low theta at prefrontal sites in the test period of 100-700 ms after stimulus onset HA exhibited relative predominance of the left hemisphere in response to both threatening and pleasant stimuli, whereas LA yielded larger right than left hemisphere activity in response to all the three stimulus categories. In the upper theta band between group differences were associated with posterior cortical regions and the test period of 0-1000 ms after stimulus onset: HA exhibited the largest ERS to threatening, whereas LA prompted the largest ERS to pleasant stimuli. Finally, according to the ERD data, in the alpha1 band HA participants in comparison with LA revealed enhanced left hemisphere activation in response to all the stimulus categories. It is suggested that as it is indexed by theta-ERS relative predominance of the left hemisphere at prefrontal sites along with the largest bilateral activity of posterior cortical regions (i.e., enhanced higher order visual processing) to threatening stimuli could form the basis for general bias towards threatening information in HA at the very early stages of emotional processing.     

Hemispheric asymmetry of the space-motion component of a food-conditioned motor reflex

The preference of movement direction in the process of motor food conditioned reaction has been investigated in rats with intact brain and after unilateral cortical inactivation. It was shown that the degree of motorspatial preference diminished with the maturation of reaction. At the high level of differentiation the valid preference was shown only in 38% of animals investigated but it was absent in the rest of animals. After inactivation of right hemisphere cortex left-side preference occurred in the presence as well as in the absence of the original preference. Inactivation of the left hemisphere cortex is less significant; it influences the original preference of movement direction permanently affecting those animals which normally had evident preference. It is concluded that the right hemisphere cortex plays dominant part in both sensor and motorspatial components of motor food conditioned reaction. It is supposed that the definite relationship exists between the degree of preference of movement direction and the functional asymmetry of cerebral hemispheres.     

Interhemispheric EEG asymmetries during unilateral bright-light exposure and subsequent sleep in humans

We tested whether evening exposure to unilateral photic stimulation has repercussions on interhemispheric EEG asymmetries during wakefulness and later sleep. Because light exerts an alerting response in humans, which correlates with a decrease in waking EEG theta/alpha-activity and a reduction in sleep EEG delta activity, we hypothesized that EEG activity in these frequency bands show interhemispheric asymmetries after unilateral bright light (1,500 lux) exposure. A 2-h hemi-field light exposure acutely suppressed occipital EEG alpha activity in the ipsilateral hemisphere activated by light. Subjects felt more alert during bright light than dim light, an effect that was significantly more pronounced during activation of the right than the left visual cortex. During subsequent sleep, occipital EEG activity in the delta and theta range was significantly reduced after activation of the right visual cortex but not after stimulation of the left visual cortex. Furthermore, hemivisual field light exposure was able to shift the left predominance in occipital spindle EEG activity toward the stimulated hemisphere. Time course analysis revealed that this spindle shift remained significant during the first two sleep cycles. Our results reflect rather a hemispheric asymmetry in the alerting action of light than a use-dependent recovery function of sleep in response to the visual stimulation during prior waking. However, the observed shift in the spindle hemispheric dominance in the occipital cortex may still represent subtle local use-dependent recovery functions during sleep in a frequency range different from the delta range.     

The hemispheric lateralization of the recognition of noisy visual stimuli in man

At tachistoscopic unilateral presentation of noisy visual stimuli and application of "yes-no" method in man predominance was found of the right hemisphere by the number and "yes" reaction time and of the left hemisphere by the number of responses "no". At verbal mnemic load preceding the presentation of visual patterns the left hemisphere asymmetry was observed by the number of "yes" responses and reactions time of both types. FMA was more clearly expressed in men in the first case and in women--in the second one. In more difficult conditions of recognition of several types of patterns, FMA was noticed mainly in women: initial left hemisphere advantage during the increase of the disturbance was changed to the right hemispheric one and appeared again. Preferential participation of the right hemisphere in singling out of the visual signal from noise is supposed. Possibility of the left hemispheric asymmetry manifestation was determined by the specificity and complexity of the visual task, by the level of the disturbance, presentation of competitive task and sexual composition of the group.     

Asymmetry of the transcallosal responses in the parietal cortex of kittens in the 1st month of life

In acute experiments on kittens the process of formation of asymmetry of transcallosal responses (TCR) was studied in multiple leads from symmetrical points of the parietal cortex. By the early positive-negative TCR complex, vanishing as a result of callosotomy, predominance of positive components in the right hemisphere was found in 2-7 days kittens, whereas in 8-24 days animals the left hemisphere dominated by both phases of responses. By the late TCR component preserved after section of the callosal body, left-hemispheric asymmetry was found in the elder group of kittens; it was absent in the younger animals. TCR asymmetry in the parietal cortex depended on the sex of the animals. With their age its inversion and enhancement took place. This process is based on the increase of TCR amplitude in the left hemisphere, with no increase in the right hemisphere.     

Dynamic spatial coding within the dorsal frontoparietal network during a visual search task

To what extent are the left and right visual hemifields spatially coded in the dorsal frontoparietal attention network? In many experiments with neglect patients, the left hemisphere shows a contralateral hemifield preference, whereas the right hemisphere represents both hemifields. This pattern of spatial coding is often used to explain the right-hemispheric dominance of lesions causing hemispatial neglect. However, pathophysiological mechanisms of hemispatial neglect are controversial because recent experiments on healthy subjects produced conflicting results regarding the spatial coding of visual hemifields. We used an fMRI paradigm that allowed us to distinguish two attentional subprocesses during a visual search task. Either within the left or right hemifield subjects first attended to stationary locations (spatial orienting) and then shifted their attentional focus to search for a target line. Dynamic changes in spatial coding of the left and right hemifields were observed within subregions of the dorsal front-parietal network: During stationary spatial orienting, we found the well-known spatial pattern described above, with a bilateral hemifield representation in the right hemisphere and a contralateral preference in the left hemisphere. However, during search, the right hemisphere had a contralateral preference and the left hemisphere equally represented both hemifields. This finding leads to novel perspectives regarding models of visuospatial attention and hemispatial neglect.     

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.     

Functionally specific reorganization in human premotor cortex

After unilateral stroke, the dorsal premotor cortex (PMd) in the intact hemisphere is often more active during movement of an affected limb. Whether this contributes to motor recovery is unclear. Functional magnetic resonance imaging (fMRI) was used to investigate short-term reorganization in right PMd after transcranial magnetic stimulation (TMS) disrupted the dominant left PMd, which is specialized for action selection. Even when 1 Hz left PMd TMS had no effect on behavior, there was a compensatory increase in activity in right PMd and connected medial premotor areas. This activity was specific to task periods of action selection as opposed to action execution. Compensatory activation changes were both functionally specific and anatomically specific: the same pattern was not seen after TMS of left sensorimotor cortex. Subsequent TMS of the reorganized right PMd did disrupt performance. Thus, this pattern of functional reorganization has a causal role in preserving behavior after neuronal challenge.     

On Disturbances of Interhemispheric Interaction in Psychopathologic States (Development of Ideas of L.Ya. Balonov and V.L. Deglin)

The current state of the problem of changes of brain functional asymmetry in psychopathology is reviewed from the point of view of disorders of interhemispheric interaction as the main chain in genesis of affective disorders and schizophrenia. Based on studies of individual activation of the left and right hemispheres as well as on evaluation of cognitive activity, it is shown that psychopathology is accompanied by a disorder of hemispheric interaction with shift of the interhemispheric activation balance towards the right hemisphere in depression and towards the left hemisphere in maniacal states and paranoid schizophrenia. Changes of the activation balance lead to disorder of cognitive activity and human adaptation in the environment. A conclusion is made that disinhibition of subcortical and brainstem structures in psychoses occurs not only vertically, but also horizontally, when the complementary and superpositional interaction of hemispheres shifts to the evolutionary earlier reciprocal type of interaction with domination of cognitive functions of the right hemisphere in depression and of the left hemisphere in the maniacal state and schizophrenia.     

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.     

Structural analysis of associative chain rows in teenagers with deviant behavior

The lexical-semantic analysis of the internal lexicon structure has shown that teenagers with deviant behavior prefer calling the words designating objects of the environment; they are characterized by the highest frequency of words and predominance of the relatively narrow circle of themes—“interior” and “food, tableware.” Thus, the lexicon nucleus is very structural and is an object component of the world image. Such lexicon structure seems to be due to predominance of the right hemisphere activity. On the contrary, in children without the deviant behavior the nucleus of the verbal cognition can be presented as bipolar: on the one hand, school, school objects, on the other hand, the world of concepts. In the latter case the space of the potential probability activity is reflected. Such lexicon structure seems to be due to predominance of the left hemisphere activity.     

Characteristics of the interhemispheric EEG relationships in assessing the functional state of the human brain

In healthy subjects (11 right-handed men) reorganization was studied of intra- and interhemispheric correlation of the electrical brain activity at transition from the state of alertness to drowsiness. At the lowering of alertness level, the coherence of hemispheres symmetrical points changed not abruptly, with a tendency towards an increase at differently directed character of changes of combinations of separate physiological rhythms ranges. Comparison of the EEG coherence changes within the right and left hemispheres revealed a greater reactivity of the left (dominant) hemisphere. The reduction of the predominance (observed in the dominant hemisphere in alertness) of the degree of EEG conjunction, at transition to drowsiness, leads to smoothing of interhemispheric asymmetry in the organization of electrical brain processes.