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.     

Hemisphere asymmetry of motor-feeding behavior of mice in a multi-alternative symmetrical maze

The behaviour of mice of BALB/c line was studied in a symmetrical multialternative Y-maze: their motor, alimentary and investigating activities as well as spatial-motor asymmetry. In animals with inactivated left hemisphere, as compared to intact ones, the motor and alimentary activities were lowered, and the investigating one augmented. Instead of the weak left-side asymmetry a distinct left-side preference appeared of most Y-maze sections, and right-side preference for approaches to the feeders. Elimination of the right hemisphere did not change the motor activity; the alimentary one decreased and the investigating one augmented, but less than during inactivation of the left hemisphere. On the whole, the right-side asymmetry appeared for all sections. According to all parameters studied, the influence of the left hemisphere on animal behaviour was more expressive and diverse. Spatial preference is formed with participation of influences of both hemispheres. The differences between them are more qualitative than quantitative.     

Differences in vulnerability between the hemispheres in early childhood and adulthood

There are more left hemisphere damaged than right hemisphere damaged children and adults if one relies on studies of congenital hemiparesis as well as on those done on groups with radiologically demonstrated perinatal and postnatal unilateral stroke, hemispherectomy, or unilateral epilepsy in childhood or adulthood. The main pathogenetic factor seems to be a hemodynamic one, responsible for insufficient blood supply to the left hemisphere. Since adults show a difference in the same direction as children, the blood supply to the left internal carotid artery would seem to be the crucial factor. Around birth, an open ductus arteriosus may play an additional role. The hemodynamic asymmetry does not exclude an intrinsic maturational hemispheric tissue factor, making the left hemisphere more vulnerable than the right to detrimental influences around birth and during the early postnatal period. Immature white matter is especially vulnerable to asphyxia. The text was submitted by the author in English.     

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.     

Cooperation or Competition of the Two Hemispheres in Processing Characters Presented at Vertical Midline

Little is known about how the hemispheres interact in processing of stimuli presented at vertical midline. Processing might be mutually independent or cooperative. Here we measured target identification and visually evoked EEG potentials while stimulus streams containing two targets, T1 and T2, were either presented at vertical midline above and below fixation, or laterally, left and right. With left and right streams, potentials evoked by filler stimuli and by T2 were earlier at the right than the left visual cortex, and T2 was better identified left than right, confirming earlier results and suggesting better capabilities of the right hemisphere in this task. With streams above and below fixation, EEG potentials evoked by filler stimuli and by T2 were likewise earlier at the right than the left hemisphere, and T2 was generally identified as well as, but not better than left T2, in one target constellation even worse (T2 in lower stream preceded by T1 in upper stream). These results suggest right-hemisphere preference for this task even with stimuli at vertical midline, and no added value through hemispheric cooperation. Lacking asymmetry for T1 amidst asymmetries for filler stimuli and for T2 might indicate alternating access of the hemispheres to midline stimuli as one means of hemispheric division of labor.     

The preference for movement direction in a T-maze in planarians

Characteristics of spatial orientation in T-maze were studied in 1768 Planaria of following types: Dugesia tigrina (sexless and sexual race), Dugesia lugubris, Ijmia tenuis, Bdellacephala punctata. It was shown that from one third to one half of individuals were characterized by asymmetry of movement direction preference. The preference of right turning was typical for Dugesia tigrina; Dugesia lugubris, Ijmia tenuis, Bdellacephala punctata preferred left turning. The asymmetry described is considered as a primitive form of species functional asymmetry.     

Interhemispheric asymmetry of positive emotional reactions in rats

Interhemispheric asymmetry of positive emotional reactions was studied in rats: satisfaction of drinking need and self-stimulation. Successive inactivation of the hemispheres was carried out by potassium spreading depression. Switching off of the right as well as the left hemispheres symmetrically influenced the whole quantity of the water, drunk by the rats to a full thirst satisfaction, i. e. the magnitude of need. However, at different stages of drinking need satisfaction an interhemispheric asymmetry was observed: under a strong drinking motivation the right hemisphere dominated, under a weak motivation--the left one. Switching off of the right hemisphere lowered the frequency of self-stimulation of the lateral hypothalamus and switching off the left one heightened it, testifying to the dominance of the right hemisphere in the reaction of self-stimulation. This reaction was also characterized by asymmetry of the lateral hypothalamus nuclei; reactivity to hemispheres inactivation (decreasing or increasing of self-stimulation frequency) of the right nucleus was more expressed than that of the left one.     

Interhemispheric asymmetry in the functional organization of the prefrontal cortex in animals of different typologic groups

Rats allocated to groups by the method of "emotional resonance": rats which did and did not escape crying of a partner (A- and E-groups, respectively). Unit activity in the right and left prefrontal brain cortex (PFC) was recorded in these rats. The recorded neurons neurons were divided in two groups according to their reaction to a change in the level of food motivation. The so-called D-neurons decreased their activity after feeding of animals after a 24-hour food deprivation and the other group (I-neurons) increased its firing rate rate in this situation. It was shown that hemispheric distributions of D- and I-neurons are different in selected rat groups. In E-rats the I-neurons substantially predominated in the left hemisphere, whereas the D-neurons were more frequently recorded in the right one. No such asymmetry was observed in A-group of rats. During intracranial stimulation of emotionally positive brain structures I-neurons increased their firing rate, predominantly, in the left hemisphere, whereas during intracranial emotionally negative stimulation activation of the D-neurons predominated at the right. Features of the observed functional interhemispheric asymmetry of prefrontal cortex in A- and E-groups of rats were explained by differences in the interaction between hemispheres and dissimilar activation control.     

The effect of sex steroid hormones on interhemispheric asymmetry in rats]

The effect of gonadectomy and sex-steroid hormones treatment on functional interhemispheric asymmetry to the reaction of pain cry avoidance of another species (emotional reactions) and motor and exploratory activity of open-field behavior in Wistar rats of 3 months old has been investigated. A spreading depression technique for hemisphere inactivation has been used. The hemispheric asymmetry of the reactions in intact rats was characterized by sex dimorphism; the left hemisphere dominated to a great extent in males than in females under the control of emotional reactions; in motor and exploratory activity in open-field behavior of rats the left hemisphere dominated in males and the right one--in female. In both sexes the neonatal gonadectomy levelled the interhemispheric differences in reactions under investigation. The following treatment of females with estradiol and males with testosterone didn't restore the asymmetry. After the castration at the age of 3 months the correlation between the size and direction of interhemispheric differences became reverse. The treatment of females with testosterone and males with estradiol both castrated in adulthood restored the interhemispheric asymmetry in males and had no effect in females. The treatment of intact rats with hormones of opposite sex led to the enhancement of left hemisphere dominance in motor and exploratory activity in males and levelled the asymmetry in females. It has been shown that in adult rats sex-steroids effect predominantly the right hemisphere.     

Differences in vulnerability between the hemispheres in early childhood and adulthood

There are more left hemisphere damaged (LHD) than right hemisphere damaged (RHD) children and adults, if one relies on studies of congenital hemiparesis, as well as on those done on groups with radiologically demonstrated perinatal and postnatal unilateral stroke, hemispherectomy or unilateral epilepsy in childhood or adulthood. The main pathogenetic factor seems to be a hemodynamic one, responsible for insufficient blood supply to the left hemisphere (LH). Since adults show a difference in the same direction as children, the blood supply factor to the left internal carotid artery would seem to be the crucial factor. Around birth, an open ductus arteriosus may play an additional role. The hemodynamic asymmetry does not exclude an intrinsic maturational hemispheric tissue factor, making the left hemisphere more vulnerable than the right to detrimental influences around birth and during the early postnatal period. Immature white matter is especially vulnerable to asphyxia.     

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.     

Crossmodal spatial influences of touch on extrastriate visual areas take current gaze direction into account

Recent results indicate that crossmodal interactions can affect activity in cortical regions traditionally regarded as "unimodal." Previously we found that combining touch on one hand with visual stimulation in the anatomically corresponding hemifield could boost responses in contralateral visual cortex. Here we manipulated which visual hemifield corresponded to the location of the stimulated hand, by changing gaze direction such that right-hand touch could now arise in either the left or right visual field. Crossmodal effects on visual cortex switched from one hemisphere to the other, depending on gaze direction, regardless of whether the hand was seen. This indicates that crossmodal influences of touch upon visual cortex depend on spatial alignment for the multimodal stimuli, with gaze posture taken into account.     

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.     

Sexual differences in the interhemispheric asymmetry of the transcallosal responses of the associative areas in the cat neocortex

Sex differences of hemisphere asymmetry of homo- and heterotopic transcallosal responses in association cortex of 48 cats (24 male and 24 female) immobilized by tubocurarine have been studied by means of topographic EPs recordings in both hemispheres. In males left hemisphere dominates by the amplitude of homotopic and positive wave of heterotopic EPs and right hemisphere dominates by the amplitude of negative wave of heterotopic sensorimotor cortex EPs. The individual asymmetry of EPs has been observed in sensomotor cortex of females and in parietal cortex of animals of both sex. The interhemispheric asymmetry is expressed distinctly in females than in males. It is concluded that sex dimorphism is present in functional organization of associative system of (callosal and intracortical) connections in cat's neocortex projection and association areas which means its more expressed hemisphere lateralization in males with more expressed interhemispheric asymmetry of functional transcallosal connections in females.     

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.     

Anatomical brain asymmetries in New World and Old World monkeys: stages of temporal lobe development in primate evolution

Relatively large (n = 20-30) samples of formalin-fixed brain specimens from five Old and New World monkey species were examined in a study measuring anatomical temporal-lobe asymmetries. Linear measurements of the length of the Sylvian fissure were taken on each cerebral hemisphere to evaluate lateral differences related to development of auditory association cortex. The results indicate significantly greater Sylvian fissure length on the left hemisphere than on the right hemisphere in four of these species. Measurements of a different parameter on Saimiri sciureus brain specimens (length of anterior portion of the Sylvian fissure) also suggested temporal-lobe asymmetry favoring the left hemisphere. Other measurements (length of the Sylvian fissure lying posterior to the central sulcus, and dorso-ventral position of the Sylvian point) in Macaca mulatta and M. fascicularis did not reveal significant right/left-hemisphere differences. Sylvian-fissure length determined from photographs of M. mulatta hemispheres in contrast to results of direct measurements did not yield significant right/left-hemisphere asymmetry. We mention possible reasons why previous anatomical studies of brains from monkeys did not discern temporal-lobe asymmetry, and we also discuss whether or not certain of these asymmetries in monkeys foreshadowed the evolution of language-processing areas of the cerebral cortex in hominids.     

Functional assymmetry of the cerebral cortex in cats during formation of a conditioned reflex

During elaboration of a symmetric active defensive reflex, the animal is given the opportunity to make instrumental movements with the right or left paw. On the first day of elaboration, the cats can be subdivided into three approximately equal groups: with the right preferred paw, with the left preferred paw and ambidexters. After stabilization of the reflex, motor asymmetry increases in both preferred groups, while the number of ambidexters diminishes. Unilateral electric shock producing seizures, which is applied to the "dominant" or "subdominant" hemisphere, exerts correspondingly differing influences on the subsequent reproduction of the reflex. Suppression of reproduction is more pronounced when the shock is applied to the "dominant" hemisphere. The result of repetitive application of electroshock to one and the same hemisphere is that the functions of the "dominant" hemisphere are effected by the hemisphere which was not subjected to direct electrical stimulation.     

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.     

The noradrenaline and serotonin content in symmetrical parts of the normal rat brain and during learning and peptide administration]

Content was compared of noradrenaline (NA) and serotonine (5-OT) in the right and left halves of the rats brain in norm, at elaboration of defensive conditioned reflexes of two-ways avoidance (CRTWA) and at administration of neuropeptides influencing the learning and memory--dezglycilargininvasopressin (DG-AVP), ACTH4-7 pro-gli-pro and dalargin. The conducted studies showed that in control animals the content of NA in the cortex of the right hemisphere was significantly higher than in the cortex of the left one. For the content of 5-OT in symmetric brain parts no significant differences were revealed. Under the elaboration of CRTWA the asymmetry of NA content was not eliminated. Systemic administration of DG-AVP, ACTG4-7 pro-gli-pro and dalargin practically did not change the content of 5-OT, but reduced the content of NA in the cortex and the rest of the brain, and the content of NA in the right and left cortex was equalized. The obtained data point to the asymmetric character of neuropeptides action and to greater resistance of 5-OT-ergic brain system to functional load and to administration of peptides in comparison with NA-ergic system.     

Decision of mathematical logical tasks in sensory enriched environment (classical music)

The time of a decision of mathematical logical tasks (MLT) was decreased during classical musical accompaniment (power 35 and 65 dB). Music 85 dB did not influence on the process of decision of MLT. Decision without the musical accompaniment led to increasing of coherent function values in beta1, beta2, gamma frequency ranges in EEG of occipital areas with prevalence in a left hemisphere. A coherence of potentials was decreased in EEG of frontal cortex. Music decreasing of making-decision time enhanced left-sided EEG asymmetry The intrahemispheric and the interhemispheric coherences of frontal cortex were increased during the decision of MLT accompanied by music. Using of musical accompaniment 85 dB produced a right-side asymmetry in EEG and formed a focus of coherent connections in EEG of temporal area of a right hemisphere.