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.     

Vervet monkeys and humans show brain asymmetries for processing conspecific vocalizations, but with opposite patterns of laterality

A robust finding in the human neurosciences is the observation of a left hemisphere specialization for processing spoken language. Previous studies suggest that this auditory specialization and brain asymmetry derive from a primate ancestor. Most of these studies focus on the genus Macaca and all demonstrate a left hemisphere bias. Due to the narrow taxonomic scope, however, we lack a sense of the distribution of this asymmetry among primates. Further, although the left hemisphere bias appears mediated by conspecific calls, other possibilities exist including familiarity, emotional relevance and more general acoustic properties of the signal. To broaden the taxonomic scope and test the specificity of the apparent hemisphere bias, we conducted an experiment on vervets (Cercopithecus aethiops)-a different genus of old world monkeys and implemented the relevant acoustic controls. Using the same head orienting procedure tested with macaques, results show a strong left ear/right hemisphere bias for conspecific vocalizations (both familiar and unfamiliar), but no asymmetry for other primate vocalizations or non-biological sounds. These results suggest that although auditory asymmetries for processing species-specific vocalizations are a common feature of the primate brain, the direction of this asymmetry may be relatively plastic. This finding raises significant questions for how ontogenetic and evolutionary forces have impacted on primate brain evolution.     

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.     

Asymmetry of Tactile Perception and Interhemispheric Interactions in Stutterers

The effect of inverse masking on the skin of the left and right hands and of bimanual reverse masking during coordinated work of both hands in stutterers was studied to detect the changes in cerebral asymmetry related to stuttering. The study showed that (1) asymmetry of tactile perception is absent in stutterers in the conditions of masking; it is supposed that when stuttering begins in early childhood, the formation of the hemispheric specialization in performing both sensory (all modalities) and speech functions is interrupted; (2) stuttering right-handers demonstrate a strongly levotropic nature of the interhemispheric interactions under conditions of bimanual masking, which testifies to a more considerable retardation of the perception of a test stimulus in the stutterers' left hemisphere under the influence of the masking stimulus in the right hemisphere than in right-handers with normal speech. It is assumed on this basis that stuttering begins because of the combination of symmetry and asymmetry in the interhemispheric relations. There is a hypothetical model that supposes that the phenomenon of stuttering is caused by two fundamental factors, namely, bilateral symmetry (existence of two identical speech centers in the right and left hemispheres) and a specific levotropic asymmetry of the interhemispheric relations, i.e., a more manifest influence of the right hemisphere on the left hemisphere in stutterers. This conditions the emergence of two identical speech impulses that appear with long intervals between them, which cause a dissonance in the functioning of the speech-forming apparatus.     

Does emotional state influence motor lateralization in California sea lions (<Emphasis Type="Italic">Zalophus californianus</Emphasis>)?

Motor lateralization is a behavioural asymmetry between the left and the right side of an individual due to hemispheric specialization. The right hemisphere controls the left side of the body and the left hemisphere the right side. The right hemisphere processes negative emotions such as fear and frustration, and on the contrary, the left hemisphere processes positive emotions such as happiness. This study, conducted at Parc Asterix Delphinarium (Plailly, France), tested the influence of supposedly positive, negative and neutral emotional situations on four California sea lions’ (Zalophus californianus) motor lateralization while performing a known exercise, here climbing on a stool. Latency between the caretakers’ command and the animals’ response was recorded. The results showed an interindividual variability in the effect of the supposed emotional situations on their motor lateralization and their response latency. The nature and the strength of this effect require deeper investigation by further studies, on a larger number of individuals and contexts.     

Sex-dependent structural asymmetry of the medial habenular nucleus of the chicken brain

Summary An investigation of structural asymmetry in the avian brain was conducted on the epithalamic medial habenular nucleus of the chicken. Twelve male and ten female two-day-old chickens were used for a morphometric evaluation of asymmetry. The medial habenular nucleus was measured from paraffin-wax-embedded, 8 m-thick sections by use of a semiautomatic image analyser. The volumes of the right and left medial habenula of each animal were statistically analysed (within animal experimental design). The right medial habenula in males showed significant group asymmetry. In contrast, females failed to demonstrate group bias in favour of either hemisphere. However, individual females were lateralised, with either a larger right or left medial habenula. Although individuals of both sexes were lateralised, there was no significant sex difference in volume in either the right or left medial habenula.We propose that sex-linked structural asymmetry may be influenced by steroid hormonal effects in the central nervous system, and that such asymmetry could be more prevalent in the non-mammalian vertebrate brain than previously considered.     

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.     

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.     

Hemispheric asymmetry of the nigrostriatal system of the brain in rats genetically predisposed to catalepsy]

Hemispheric asymmetry of nigro-striate system in a strain of rats GC bred from Wistar for a predisposition to cataleptic reaction was studied by means of biochemical and morphological methods. Hemispheric asymmetry was found in GC and Wistar rats with respect to aminopeptidase activity in neurons of caudate nucleus, with a more pronounced left-side increase in GC rats, the asymmetry index being 13.7%. Acetylcholine esterase activity in subcellular particles of caudate nucleus showed an inversion of asymmetry with higher activity in the left hemisphere of Wistar and right hemisphere of GC rats, and asymmetry index of 15.5%. With respect to the number of astroglia cells in S. nigra, and astroglia and oligodendroglia in N. accumbens there was also an inversion of asymmetry in GC rats who had more cells in the structures of the left hemisphere, whereas Wistar rats had more in the right hemisphere. The asymmetry index was high and equal to 29.8% for astroglia in S. nigra, and 17% for astroglia and 21.4% for oligodendroglia in N. accumbens. However, in S. nigra the number of neurons and oligodendroglia cells was equally increased in the right hemisphere in GC and Wistar rats. The data suggest that the mechanism of hereditary pathology of brain nigro-striate system involves both enhancement and inversion of the hemispheric asymmetry.     

Hemispheric asymmetry of visual evoked potentials during human recognition of facial emotional expressions

Visual evoked potentials (VEP) in standard 16 EEG derivations were recorded in 26 young men and 20 women during recognition of facial emotional expressions and geometric figures. The stimuli were presented on a computer screen in the center of the visual field or randomly in the right or left vision hemifields. Peak VEP latency and mean amplitude in 50-ms epochs were measured; spatiotemporal VEP dynamics was analyzed in a series of topographic maps. The right hemisphere was shown to be more important in processing emotional faces. The character of the asymmetry was dynamic: at earlier stages of emotion processing the electrical activity was higher in the right inferior temporal region compared to the left symmetrical site. Later on the activity was higher in the right frontal and central areas. The dynamic mapping of "face-selective" component N180 of VEPs revealed the onset of activation over the right frontal areas that was followed by the fast activation of symmetrical left zones. Notably, this dynamics didn't correlate with the hemifield of stimuli exposition. The degree of asymmetry was lower during presentation of figures, especially in the inferior temporal and frontal regions. The prominent asymmetry of information processes in the inferior temporal and frontal areas was suggested to be specific for recognition of facial expression.     

Physical criteria of pathological processes. I. Change in the functional hemispheric asymmetry at various stages of rheumatic diseases]

The functional interhemispheric asymmetry of brain in patients with systemic rheumatic diseases was estimated by measuring brain direct current potentials. It is shown that different types of functional interhemispheric asymmetry correspond to different stages of systemic rheumatic diseases. At early stages, the left hemisphere asymmetry dominates, at expressed stages, the right hemisphere asymmetry is prevalent, and the terminal stage is characterized by the loss of functional interhemispheric asymmetry.     

正常儿童多导视觉诱发电位的非对称性分布

对４９名正常儿童进行了多导视觉诱发电位的观察。结果表明：（１）双眼及单眼ＶＥＰｓ波形在头皮中线两侧分布是非对称性,右偏者较左偏者多,这种非对称性可能与脑组织两侧结构和功能的不对称有关,从而影响到ＶＥＰｓ发生源的位置以及偶极子的方向及强度等。（２）吉利手者右半视野刺激的ＶＥＰｓ振幅,（ＡｎｌＰ１）大于左半视野刺激的ＶＥＰｓ振幅,两半球枕叶皮层神经解剖学上的非对称性为我们的电生理结果提供了一定的形态结构基础。（３）半视野刺激显示“矛盾定侧”现象。     

Diversity and convergence in the mechanisms establishing L/R asymmetry in metazoa

Differentiating left and right hand sides during embryogenesis represents a major event in body patterning. Left–Right (L/R) asymmetry in bilateria is essential for handed positioning, morphogenesis and ultimately the function of organs (including the brain), with defective L/R asymmetry leading to severe pathologies in human. How and when symmetry is initially broken during embryogenesis remains debated and is a major focus in the field. Work done over the past 20 years, in both vertebrate and invertebrate models, has revealed a number of distinct pathways and mechanisms important for establishing L/R asymmetry and for spreading it to tissues and organs. In this review, we summarize our current knowledge and discuss the diversity of L/R patterning from cells to organs during evolution.     

Development of asymmetry in the caenogastropods Amphissa columbiana and Euspira lewisii

Abstract. The asymmetry displayed by the body plan of gastropods has been directly or indirectly attributed to an evolutionary process called torsion. Torsion is defined as a rotation of 180° between the cephalopodium (head and foot) and visceropallium (visceral organs, mantle, mantle cavity, and shell). During development, the displacement of anatomical components occurs during a process called "ontogenetic torsion." Although ontogenetic torsion is central to theories of gastropod evolution, surprisingly few studies have documented actual tissue movements during the development of asymmetry in gastropods. We investigated the development of the mantle cavity and pleurovisceral nerve connective (visceral nerve loop) in the caenogastropods Amphissa columbiana and Euspira lewisii , because displacements of both of these structures are interpreted as major consequences of torsion. Scanning electron micrographs, histological sections, and immunofluorescence images showed that the developing vis-ceropallium twists by 90° relative to the cephalopodium, the mantle cavity initially forms on the right side, and displacements of the visceral nerve loop become evident on the left side before the right side. A developmental stage in which the mantle cavity is confined to the right side has also been reported in members of the Vetigastropoda and Heterobranchia. We suggest that further comparative studies should test the hypothesis that early development throughout the Gastropoda converges on an embryonic organization in which the mantle cavity and anus are located laterally, despite clade-specific differences in developmental patterns both before and after this stage.     

Hemispheric interaction in man during perception of visual stimuli]

Averaged evoked potentials (AEP) to verbal (letters) and nonverbal (random shapes) stimuli exposed in the left and right visual fields were registered in healthy subjects with normal vision. Analysis of the later AEP latencies pointed to asymmetry in the temporal parameters of the interhemispheric interaction. The late AEP latency is shorter in the right hemisphere than in the left hemisphere. The difference is more pronounced in responses to nonverbal stimuli. The earlier development of the evoked potential in the right hemisphere (or the later one in the left hemisphere) accounts for the interhemispheric difference in the temporal parameters of the late AEP components. Comparison of the latency of the component P300 to verbal and nonverbal stimuli presented in the ipsilateral or the contralateral visual fields reveals a transfer of the results of the cortical processing of visual information in the course of interhemispheric interaction.     

Characteristics of functional asymmetry in small premature infants at an age of 13–14 months

Delayed consequences of a sharp shortening of the prenatal period for the formation of handedness and the function of visuospatial attention were analyzed. The test group consisted of 16 small premature (SP) children at a corrected age of 13–14 months. The functional asymmetry was assessed by means of the A-not-B neuropsychological task, which is arranged in such a way that a child has to look for an attractive object in either a left or a right location. As compared to healthy children of the same age, the functional asymmetry of SP children was characterized by the absence of right-handedness. During the performance of the A-not-B trials, the SP children displayed a distinct left-side asymmetry: trials with an object hidden to the right of the child were significantly more frequently erroneous than those with a left-side position of the object. It is suggested that SP children have problems with disengagement of the attentional focus from an object located in the left half-field of vision under the conditions of shifting the attention to the right half-field. Probably, one of the consequences of a sharp decrease in the period of prenatal development is abnormal lateralization of some brain functions.     

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.     

Lateralized ultradian rhythms of the right and left brain: temporal variations of tactile discrimination tested in German subjects.

Endogenous ultradian rhythms with a periodicity of 2-3 hours operate separately in the right and left hemispheres of the human brain and modulate physiological functions, perception and cognition. Since sensory pathways from either hand terminate in the contralateral hemisphere, ultradian rhythms of the right and left brain can be monitored by variations in the tactile discrimination of the left and right hand, respectively. Thirteen right-handed German males were tested every 15 minutes for 8 hours. Time series of the tactile error rate determined for the right and left hands oscillate with significantly different ultradian periodicities. Whereas cycles in tactile discrimination of the right hand (left hemisphere) have a periodicity of about 2 hours, tactile discrimination of the left hand (right hemisphere) is modulated by longer periods of about 3 hours. This is interpreted in terms of the overall functional asymmetry of the human brain. Since the left brain is the specialized locus for verbal processing and the right brain for visual-spatial processing, lateralized ultradian rhythms operating in the hemispheres may provide a distinct frame for long-term timing of neuronal processes underlying semantic and spatial mapping of the environment. This is particularly important for interpreting biosocial behavioural rhythms seen in humans living under natural conditions.     

Interhemispheric motor asymmetry of conditioned feedback

The interhemispheric asymmetry and lateralization of motor functions, as applied to backward conditioning, was studied in two dogs that afterwards turned to be a right-hander and a left-hander. In the process of food-procuring instrumental conditioning it was revealed that one of the dogs predominantly used the right paw (with the dominance of the left hemisphere) and the second animal used the left paw (the right brain hemisphere dominated). The earliest signs of lateralization of the motor functions were observed in the backward conditioned connections (which had been formed earlier than the direct connections or direct conditioned reflexes). Consequently, the presence and sign of asymmetry can be predicted on the basis of manifestation of the backward connections observed at the early stages of acquisition of food-procuring behavior. The backward connections are strictly specific and have the same lateralization as the direct ones.     

Features of Psychomotor Responses and Interhemispheric Relationships at Various Stages of Adaptation to a New Time Zone

Motor response precision (MRP) as dependent on the functional asymmetry of the hands was analyzed before and after transmeridian flights across seven time zones. The MRPs of the two hands were relatively balanced under normal conditions and asymmetrical under conditions of immediate or late adaptation to a new time zone. The functions of the right hemisphere were affected mainly by acute desynchronosis, and those of the left hemisphere, by latent desynchronosis. As the functional indices and circadian biorhythms normalized, the initial domination of the left hemisphere strengthened.