Organization of Regional Interactions of the Brain Cortical Activity during the Common-root Word Derivation Task

This study analyzed specificities in the activity of the neurophysiological mechanisms underlying the organization of active word-derivation processes. The regularities in the reorganization of the spatial structure for the systemic interaction of bioelectrical activity between different cortical areas of the cerebral hemispheres were studied in adult subjects during the test for mental derivation of common root words (i.е., using the modern methods of the so-called “functional connectome” investigations). Сross-correlation and coherent analysis of EEG has shown that the ipsilateral statistical EEG interactions in the left hemisphere, including Broca’s and Wernicke’s areas, were significantly increased in adults during mental derivation of common root words and, simultaneously, the interhemispheric connectivity and the EEG interactions in the right hemisphere were reduced. Comparison of our results with the previous data of verbal activity associated with speech perception and production has revealed significant differences in the degree of involvement of the left and right hemisphere cortical activity in verbal processing. For example, unlike the data of current study, an equal involvement of both hemispheres cortical activity was recorded during the phoneme recognition in auditory perceived words, grammatical and semantic errors in sentences, as well as during mental formation of words from a set of phonemes and sentences from a set of words, which was particularly manifested in the increased of hemispheric interactions, predominantly, in the inferior frontal and temporal areas and the overlapped areas of the temporal, parietal, and occipital cortical zones (TPO) of both hemispheres. Thus, the data obtained in this study indicate the presence of expressed specificities in the lateralization of activity in the neurophysiological mechanisms underlying the processes of active word derivation and inflexion.     

Association Process and Functional Brain Asymmetry

Analysis is presented of word associations produced by subjects with left hemispheric (group 1), right hemispheric (group 2), and bilateral (group 3) speech representation. The strategy for producing extralinguistic responses was found to prevail over the strategy for producing linguistic associations in all subjects, irrespective of their type of speech representation. This strategy was more pronounced in subjects with right hemispheric speech laterality, suggesting a correlation between the generation of extralinguistic associations and functional brain asymmetry. Producing linguistic associations also depended on the type of cerebral organization of speech. The most important linguistic associations are syntagmatic. Syntagmatic associations were more closely related to the lateralization of speech to the left hemisphere. The data are compared to the results of studies of the ontogeny of associative processes.     

Modern view of cortical control of posture and brain asymmetry: a literature review

Review concerns cortical mechanisms of postural control. Data on different role of the right and the left cerebral hemispheres in postural control are analyzed. These data are compared with the data on lateralization of perception and action. Peculiarities of sensory perception and motor control in the right and the left hemispheres are supposed to be connected with the specialization of the left hemisphere on the dynamic tasks and of the right hemisphere on the static tasks which include orthograde posture control in human beings.     

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.     

Cerebral Asymmetry of fMRI-BOLD Responses to Visual Stimulation

Hemispheric asymmetry of a wide range of functions is a hallmark of the human brain. The visual system has traditionally been thought of as symmetrically distributed in the brain, but a growing body of evidence has challenged this view. Some highly specific visual tasks have been shown to depend on hemispheric specialization. However, the possible lateralization of cerebral responses to a simple checkerboard visual stimulation has not been a focus of previous studies. To investigate this, we performed two sessions of blood-oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) in 54 healthy subjects during stimulation with a black and white checkerboard visual stimulus. While carefully excluding possible non-physiological causes of left-to-right bias, we compared the activation of the left and the right cerebral hemispheres and related this to grey matter volume, handedness, age, gender, ocular dominance, interocular difference in visual acuity, as well as line-bisection performance. We found a general lateralization of cerebral activation towards the right hemisphere of early visual cortical areas and areas of higher-level visual processing, involved in visuospatial attention, especially in top-down (i.e., goal-oriented) attentional processing. This right hemisphere lateralization was partly, but not completely, explained by an increased grey matter volume in the right hemisphere of the early visual areas. Difference in activation of the superior parietal lobule was correlated with subject age, suggesting a shift towards the left hemisphere with increasing age. Our findings suggest a right-hemispheric dominance of these areas, which could lend support to the generally observed leftward visual attentional bias and to the left hemifield advantage for some visual perception tasks.     

Role of the Right- and Left-Hemispheric Structures in Speech and Memory Formation in Children

The role of structures of the left and right cerebral hemispheres in formation of speech function and memory was studied on the basis of complex examination of children with developmental speech disorders. On the basis of EEG estimation of the functional state of the brain, children were classified in two groups depending on the side of localization of changes in electrical activity: those with local changes in electrical activity in the left hemisphere (group I) and those with changes in the right hemisphere (group II). The medical history suggested that the observed features of topography of local changes in electrical activity were linked with the character of prenatal and labor complications and their consequences leading to embryo- and ontogenetic disorders in development of different brain regions. Comparison of the results of neuropsychological examination of the two groups showed that different regions of the brain cortex of both the left and right hemispheres are involved in speech formation. However, a specific role of the right hemisphere in formation and actualization of automatic speech series was revealed. It was suggested that the integrity of gnostic functions of the right hemisphere and, primarily, the spatial organization of perception and movements is a necessary factor of development of auditory–speech and nominative memory.     

Free Fatty Acid Content and Release Kinetics as Manifestations of Cerebral Lateralization in Mouse Brain

Free fatty acid (FFA) content was analyzed in mouse cerebral hemispheres and cerebellum under basal and postdecapitative ischemic conditions. Total FFA content immediately after decapitation (2 s) was about two-fold higher in the left hemisphere than in the right. Marked dissimilarities between hemispheres were also apparent when FFA levels were measured during short periods of ischemia. Whereas in the right side a significant FFA release took place as early as 10 s, no accumulation was detected in the left in the 2-20 s interval. The highest rates of total fatty acid release occurred in the 20-30 s interval in both hemispheres and decreased afterwards (3 min). Individual FFA, especially stearate and arachidonate, differed in their rates of production, the right cerebral hemisphere being more active in releasing arachidonic acid. In cerebellum, FFA levels were lower and accumulation was slower than in cerebrum in both intervals. When subjected to 3 min ischemia, the same difference in FFA levels between right and left hemispheres (50%) was observed in heads kept at 20 or 30 degrees C. The differences between hemispheres are interpreted as manifestations of an inherent lateralization in the regulation of acylation-deacylation reactions of complex lipids.     

A Shared Neural Substrate for Mentalizing and the Affective Component of Sentence Comprehension

Using event-related fMRI in a sample of 42 healthy participants, we compared the cerebral activity maps obtained when classifying spoken sentences based on the mental content of the main character (belief, deception or empathy) or on the emotional tonality of the sentence (happiness, anger or sadness). To control for the effects of different syntactic constructions (such as embedded clauses in belief sentences), we subtracted from each map the BOLD activations obtained during plausibility judgments on structurally matching sentences, devoid of emotions or ToM. The obtained theory of mind (ToM) and emotional speech comprehension networks overlapped in the bilateral temporo-parietal junction, posterior cingulate cortex, right anterior temporal lobe, dorsomedial prefrontal cortex and in the left inferior frontal sulcus. These regions form a ToM network, which contributes to the emotional component of spoken sentence comprehension. Compared with the ToM task, in which the sentences were enounced on a neutral tone, the emotional sentence classification task, in which the sentences were play-acted, was associated with a greater activity in the bilateral superior temporal sulcus, in line with the presence of emotional prosody. Besides, the ventromedial prefrontal cortex was more active during emotional than ToM sentence processing. This region may link mental state representations with verbal and prosodic emotional cues. Compared with emotional sentence classification, ToM was associated with greater activity in the caudate nucleus, paracingulate cortex, and superior frontal and parietal regions, in line with behavioral data showing that ToM sentence comprehension was a more demanding task.     

Disorders of System Brain Activity in Children with Motor (Expressive) Alalia

Motor alalia refers to a number of disorders of expressive speech that are caused by the dysfunction of cerebral structures in the period when the formation of the speech system is not complete. This form of speech disorder is considered as a language disorder characterized by a persistent disturbance of the assimilation of a system of linguistic units. The possible cause of deviations in the development of speech function in children is a disproportion in the levels of development of speech structures in the left and right hemispheres, and this temporary dominance is often associated with an increased activity in the right hemisphere. According to the results of electroencephalographic studies, in children aged five to six years, there are two types of changes of the bioelectric potential system interaction of the brain cortex. The disorders of the spatial organization of interregional EEG correlations are more pronounced in either the left or right hemispheres of the brain. Thus, motor alalia can be accompanied either by disturbances in the interaction between Broca’s and Wernicke’s areas of the left hemisphere, or between symmetrical areas of the right hemisphere.     

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.     

Reorganization of interhemispheric interactions during verbal-mental activity aimed at synthesis of words and sentences

Correlation and coherence analyses of multichannel electroencephalogram (EEG) recordings from 18 subjects (mean age 25 years) were used for investigating the reorganization of systemic interactions between bioelectric potentials of the cortical areas of both hemispheres (20 EEG derivations) during verbal-mental activity connected with generating verbal units from simpler components. When generating either words from aurally presented phonemes or sentences from a set of words, the subjects exhibited specific changes in the spatial structure of the statistical relationships in the EEG, with a significant increase in the interhemispheric interactions. During performance of both tasks, the changes in the interhemispheric interactions were most pronounced in the temporal, temporo-parieto-occipital (TPO), inferofrontal, and occipital areas of both hemispheres. Phonemic synthesis was associated with a more marked increase in the contralateral interactions in the left hemisphere, and generating sentences from words, in the right hemisphere. The coherence analysis of the EEG showed the greatest changes in the Δ, ?, and β frequency bands, with rather slight changes in the α frequency band. For all frequency bands, changes in the EEG coherences were the greatest in Wernicke’s and the TPO areas of the right and left hemispheres during the performance of both tasks, especially during the phonemic synthesis. These findings suggest that neurophysiological processes underlying mental generation of words and sentences require coordinated activity of the left and right hemispheres, which is accompanied by an increase in the interhemispheric interactions in the EEG, especially in the temporal, inferofrontal, and TPO areas.     

Getting a Grip on Memory: Unilateral Hand Clenching Alters Episodic Recall

Unilateral hand clenching increases neuronal activity in the frontal lobe of the contralateral hemisphere. Such hand clenching is also associated with increased experiencing of a given hemisphere’s “mode of processing.” Together, these findings suggest that unilateral hand clenching can be used to test hypotheses concerning the specializations of the cerebral hemispheres during memory encoding and retrieval. We investigated this possibility by testing effects of unilateral hand clenching on episodic memory. The hemispheric Encoding/Retrieval Asymmetry (HERA) model proposes left prefrontal regions are associated with encoding, and right prefrontal regions with retrieval, of episodic memories. It was hypothesized that right hand clenching (left hemisphere activation) pre-encoding, and left hand clenching (right hemisphere activation) pre-recall, would result in superior memory. Results supported the HERA model. Also supported was that simple unilateral hand clenching can be used as a means by which the functional specializations of the cerebral hemispheres can be investigated in intact humans.     

The Lateralizer: a tool for students to explore the divided brain

Despite a profusion of popular misinformation about the left brain and right brain, there are functional differences between the left and right cerebral hemispheres in humans. Evidence from split-brain patients, individuals with unilateral brain damage, and neuroimaging studies suggest that each hemisphere may be specialized for certain cognitive processes. One way to easily explore these hemispheric asymmetries is with the divided visual field technique, where visual stimuli are presented on either the left or right side of the visual field and task performance is compared between these two conditions; any behavioral differences between the left and right visual fields may be interpreted as evidence for functional asymmetries between the left and right cerebral hemispheres. We developed a simple software package that implements the divided visual field technique, called the Lateralizer, and introduced this experimental approach as a problem-based learning module in a lower-division research methods course. Second-year undergraduate students used the Lateralizer to experimentally challenge and explore theories of the differences between the left and right cerebral hemispheres. Measured learning outcomes after active exploration with the Lateralizer, including new knowledge of brain anatomy and connectivity, were on par with those observed in an upper-division lecture course. Moreover, the project added to the students' research skill sets and seemed to foster an appreciation of the link between brain anatomy and function.     

Cerebral lateralization for motor tasks in simulated microgravity a Transcranial Doppler technique for astronauts

In Space, central cognitive operations are unaffected but humans are slower in perceptual-motor performance. Transcranial Doppler ultrasonography was used to monitor blood flow velocity in both middle cerebral arteries during unilateral and bilateral fingers' movements before, during and after -6 degrees 24 hours of head-down tilt (HDT) in 14 (8 males and 6 females) subjects. Physiologic hemisphere dominance was assessed by breath-holding test. There was a significant main effect of motor task, F(4, 328) = 16.05, p<0.00000001, MSe = 48.2. There was a gender vs head-position interaction F(3,246) = 4.90 p<0.002) MSe = 120. At pre-HDT females were right lateralized and males were left lateralized. A left shift in lateralization pattern was seen during 24hrs-HDT for both genders. There was a significant main effect of breath-holding test and a breath-holding test vs head position vs motor task interaction. HDT alters cerebral lateralization for motor control and this may be responsible for slowing in perceptual-motor performance in Space. TCD monitoring may be required for motor performance tasks in Space.     

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.     

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。     

Marijuana: Differential effects on right and left hemisphere functions in man

Marijuana, smoked at moderate doses, produced a differential impairment of the reaction times of right-handed males to pictorial stimuli presented to the left and right cerebral hemispheres. After smoking marijuana responses to pictorial stimuli presented to the right hemisphere were slowed significantly less than to the left hemisphere. Responses to verbal stimuli (trigrams) were slowd equally in both hemispheres, preserving an initial left hemisphere superiority for this material. This suggests that marijuana may differentially change the processing speed or relative dominance of man's two cerebral hemispheres, depending on the nature of the material being processed.     

Systemic Interaction of the Cortical Areas during Performance of Verbal–Mnestic Activity

The dynamics of the interregional interaction of cortical areas was studied in adult test subjects who accomplished the tasks of listening to and memorizing a poem and of mental arithmetic. Analysis of the spatial and temporal relations of the oscillations of the brain biopotentials showed the participation of many regions of the left and right hemispheres in the verbal–mnestic activity. The interaction was most expressed between the posterior regions of the left hemisphere and the anterior regions of the right one. To find out whether these data agree with the classical concepts on the leading role of the left hemisphere in speech activity, the authors examined 3- and 4-year-old children with motor alalia. A comparison of 3-year-old alalics with the control group of healthy children of the same age demonstrated a marked weakening of the distant interaction of the activity of the ipsilateral antero- and posterotemporal regions of the left hemisphere (i.e., those that correspond to the Broca area and Wernicke zone) both between themselves and with the activity of other cortical regions of both hemispheres. These results confirm the important role of both the inter- and intrahemispheric relations, especially those between the Broca area and the Wernicke zone, in realizing verbal–mnestic functions. A significant weakening of the systemic interaction between EEG oscillations in these areas in alalic children suggests that the auditory feedback plays a special role during speech production in the ontogenetic development of the neurophysiological mechanisms that are responsible for speech function formation.     

Effects of thymosin and B-activin on lateralization of sensomotor control in rats

Characteristics of regulatory effects of B-activin and thymosin (fraction 5) on the activity of right and left hemispheres were studied in rats. The results obtained were estimated basing on the analysis of the following components of food-searching behavior: lateralization of a single conditioned-reflex response; preference of right or left paw; spontaneous rotations. Opposite effects of thymosin and B-activin were found at different stages of the food-searching behavior. Thymosin activated structures of the left hemisphere. A conclusion is made on the possibility of application of these drugs for targeted influencing the balance of intra-hemispheric activity in the brain functional pathology and during the compensatory process.