Dynamics of Parameters Characterizing the Energy Metabolism of the Rat Cerebral Cortex At Late Stages of Ontogeny

Parameters that characterize the energy metabolism of the brain—the field potential and temperature of the cerebral cortex—were studied in rats of different ages. The results showed that, at late ontogenetic stages, these nonspecific parameters of energy metabolism undergo multiphasic changes which are qualitatively similar in both hemispheres. The interhemispheric temperature and electrophysiological gradients are maintained throughout individual development, which is regarded as a factor accounting for asymmetry in the aging of the cerebral hemispheres. The problem of age-related changes in energy expenditures for the maintenance of these interhemispheric gradients is discussed. It is suggested that the multiphasic dynamics of the parameters studied are associated with changes in the type of control over metabolic processes and cerebral functions providing for the maintenance of homeostasis in different periods of life.     

Dependence of the organization of human brain electrical activity on hemispheric dominance

In healthy subjects, in a state of relative rest, with different individual profiles of asymmetry (20 right-handed and 10 left-handed subjects), a greater conjunction of electrical brain processes (estimated by mean EEG coherence levels) has been found in the dominant hemisphere as compared to the subdominant one, more distinctly expressed in the right-handed subjects. The maximum degree of interhemispheric asymmetry of the EEG coherence is observed in the posterior associative cortical areas. Specific interhemispheric theta-range differences are revealed as compared with other EEG frequency bands. Greater values are obtained of the correlation of the EEG symmetrical hemispheres points in the whole frequency band and in alpha- and beta-ranges in the right-handed subjects than in the left-handed ones.     

Paradoxical bilateral asymmetry in bone size and bone mass in the hand

Among 227 chronic renal disease patients, micrometer caliper radiogrammetric measurements of the second metacarpal at midshaft showed the right metacarpal to be larger (with greater bone area) and with a greater cortical area than the left second metacarpal, both in 208 right-handed individuals and in 19 left-handed individuals. This direction of asymmetry was individually characteristic of the majority of individuals, whether right-handed, left-handed or ambidextrous.     

Interhemispheric interactions in right- and left-handed individuals based on EEG coherence data

The functions of interhemispheric EEG coherence were analyzed in 12 healthy subjects with the right individual profile of motor and sensor asymmetry and 7 subjects with the left profile in 2 experimental conditions: the state of rest and photostimulation of the central visual field. It was shown that in the rest condition the right-handed subjects have the higher values of EEG coherence in the thetal band in symmetrical frontal and central areas than the left-handed. These differences decreased for the frontal and central areas during activation caused by photostimulation but increased in the theta 2 and betal bands in symmetrical temporal areas (the coherence in the left-handed being higher). The difference in the EEG coherence between conditions was greater for the frontal and central areas in the right-handed than in the left-handed, especially, for the theta 1 and theta 2 bands. These findings suggest that the left-handed subjects have a less developed hierarchy of subcortical control of the functional state shifts than the right-handed.     

The AEP T-complex to synthesised musical tones: left-right asymmetry in relation to handedness and hemisphere dominance

Auditory evoked potentials were recorded to onset and offset of synthesised instrumental tones in 40 normal subjects, 20 right-handed for writing and 20 left-handed. The majority of both groups showed a T-complex which was larger at the right temporal electrode (T4) than the left (T3). In the T4-T3 difference waveforms, the mean potential between latencies of 130 and 165 ms was negative in all right-handed subjects except two for whom the waveforms were marginally positive-going. Amongst the left-handers, however, this converse asymmetry was seen in 7 subjects, 5 of them more than 2 standard deviations from the mean of the right-handed group. The degree of asymmetry was not significantly correlated with the degree of left-handedness according to the Edinburgh Handedness Inventory. Asymmetry of the T-complex to instrumental tones appears to reflect the lateralisation of auditory `musical' processing in the temporal cortex, confirming evidence from other sources including PET that this is predominantly right-sided in the majority of individuals. The proportion of left-handers showing the converse laterality is roughly in accordance with those likely to be right-hemisphere-dominant for language. If linguistic and `musical' processes are consistently located in opposite hemispheres, AEPs to complex tones may prove a useful tool in establishing functional lateralisation.     

On the handedness of Japanese monkeys

Forty-one monkeys living on the Koshima Island were tested for handedness by throwing a peanut 10 or 20 times toward each subject and recording which hand was used to pick it up. Handedness was judged at the 5% level of confidence. Animals showing no preference for the left or right hand after 20 trials were considered to be ambidextrous. The following distribution of handedness was found: left-handed, 17 (41%); right-handed, 8 (20%); ambidextrous, 16 (39%). These findings were compared with other studies on the handedness of Japanese monkeys. Handed monkeys outnumber the ambidextrous ones and the left-handed monkeys outnumber the right-handed ones. The characteristic distribution of handedness was shown to be irrespective of troop. By looking over the data from these different sources, the proportions of the left-handed, the ambidextrous, and the right-handed in Japanese monkeys were estimated at 39%, 33%, and 28% respectively. The method used in this study was compared withKawai's catching behavior and reasons for disagreement between judgments of handedness were discussed.     

Lateral differences in GABA binding sites in rat brain

An asymmetric distribution of GABA binding sites was found in the cerebral cortex, hippocampus, cerebellar hemispheres, striatum, and thalamus. Higher levels of [³H]GABA binding were observed in the left-side of most brain areas and in a greater percentage of adult rats, but the opposite asymmetry was found in the thalamus. A similar left-right difference in cerebral hemispheres was also found in five day-old rats, suggesting the genetic predetermination of asymmetry.     

The role of individual characteristics and learning in the manifestation of motor asymmetry in rats

Relative role was studied of the "initial" preference (caused by animals individual properties) and learning in real preference of one limb in rats. After a short-time learning to get food from a narrow horizontal pipe only by the left paw a retrograde amnesia was evoked in rats. At preference determination after three weeks, in conditions which allowed to get food by any paw, in the group of animals without amnesia the number of the left-handed rats was 5.7 times more than of the right-handed ones. In the group of animals with amnesia the numbers of the left-handed, right-handed and ambidextrous were approximately equal. Correlation was revealed between the speed of learning to get food by the left paw and the number of attempts to use the right paw. It has been shown that the initial preference may be stably changed even by a short-time learning (3 food seizures). By the degree of manifestation of the initial preference the rats form a continuum with a gradual transition from pronounced right-handed animals to pronounced left-handed ones. The weaker is the initial preference, the greater the role of learning in the real preference of one of the paws.     

The effect of gonadectomy on interhemispheric asymmetry in rats

The influence was studied of the gonadectomy in the newborn and mature male and female rats on functional interhemispheric asymmetry of the reaction of avoidance of pain scream of another rat ("emotional resonance"), and motor and investigatory activity in the open field. Consecutive inactivation of the hemispheres was realized by K+ spreading depression. It has been shown that neonatally gonadectomized rats have no interhemispheric asymmetry of the studied reactions. In male rats gonadectomized in mature state, interhemispheric asymmetry of "the emotional resonance" reaction is not significant and in the motor and investigatory activity in the open field, in contrast to intact animals, the right hemisphere is dominant and not the left one. Ovariectomy of mature female rats led to the increase of the dominance of the left hemisphere in the control of "the emotional resonance" and change of the right hemispheric dominance in the control of the motor and investigatory activity in the open field for the left hemispheric one. Gonadectomy of male and female mature rats had an opposite effect on the functioning of the right hemisphere: facilitating in male rats and inhibitory in female ones.     

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.     

The dynamic characteristics of the interhemispheric correlations of the EEG during the recovery of human neuropsychic activities

In patients (34 right-handed) in remote terms of cerebral trauma (CT) characteristics were studied of interhemispheric EEG correlations depending on lateralization of lesion in comparison with healthy subjects (20 right-handed). Disturbance of neuropsychic activity in patients with CT before treatment was accompanied by changes of interhemispheric asymmetry of conjunction in the form of a decrease of coherence values in the injured hemisphere; the decrease of conjunction values of symmetric cortical zones was determined by laterality of the lesion. After treatment the most effective restoration of neuropsychic activity and of interhemispheric EEG correlations was in patients in whose dynamics of the restoration process the stage of the right hemisphere activation was observed. This stage came earlier and restoration period was shorter in patients with the left hemisphere lesion.     

Psychophysiological and neurophysiological features of the organization of visuo-spatial performance in right-handed and left-handed six- to seven-year-old children

The developmental features of individual components of the visual perception and brain functional organization during visuo-spatial activity of different complexity were studied in right-handed and left-handed 6–7-year-old children. The results of psychophysiological testing of their visual perception testify to the underdevelopment of the mechanisms of integrative brain activity. Some specific features of the brain functional organization were revealed in the left-handed children during visuo-spatial performance. More autonomous functioning of the cerebral hemispheres and the duplication of the activation processes in the right and left hemisphere during visuo-spaital performance of different complexity are characteristic of these children. This is probably associated with the involvement of compensatory mechanisms, which enable the performance reliability.     

The dynamics of the brain heat fields of rats in the late postresuscitation period during stress]

By thermoencephaloscopy method the temperature relief of the rats cerebral cortex was studied after the clinical death and reanimation. The rehabilitation of the animals neurological status was completed in 1-2 days. In the remote postresuscitation period (up to 2 months), expressed disturbances were revealed of the background thermomaps and of thermal reactions of the cerebral hemispheres, evoked by the stress influence. Pathologic mosaics of thermal characteristics was revealed in conditions of relative rest and disturbance of dynamics of the brain temperature reactions and the character of interhemispheric asymmetries at stress influence. Individual character is pointed out of postreanimative pathology, which is manifest both in the background thermomaps and after the functional load. The results of the studies suggest the importance of individual approach in rehabilitation therapy of postreanimative disease.     

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.     

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.     

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 functional testing of the interhemispheric asymmetry in the spatial organization of rabbit cortical potentials]

Interhemispheric asymmetry was studied of spatial-temporal potentials organization (STPO) of the cortex in non-fixated animals in the states of deep rest, behavioural activity and in the transition period between them. Despite the intrahemispheric differences of the STPO in each of these states, interhemispheric divergences in the character of reconstructions of momentary topograms of the cortical potentials, recorded at 24-channels leading, are limited by 35% of the epoch analysis time. Comparison of the dynamics of intrahemispheric changes of topograms of cortical potentials in the left and right hemispheres in the states of rest and activity revealed a narrowing of temporal period of the absence of resemblance in reconstructions of successive topograms of the left and right hemispheres in comparison with transition processes. In the phase of rest the interhemispheric conjugation of spatial reconstructions in topograms became lowered mainly because of the disturbances of monotony of changes of their reliefs in one of the hemispheres in turn. In the active phase, deviations from STPO of the cortex, characteristic of the state of rest, were met more frequently in the right hemisphere; in that case oscillations of the topograms general mean level connected with the activity of non-specific activating subcortical brain system acquired a significant role in regulation of interhemispheric relations. Presence of interhemispheric resemblance of reconstructions of topograms reliefs in the active phase, despite the tendency to its lowering in comparison with the rest, testifies to the contribution also of the intracortical processes to the interhemispheric spatial synchronization of the cortical potentials in this state.     

Characteristics of interhemispheric relationships in the absence or presence of a skill

A comparative analysis of the time and amplitude characteristics of the negative N200 and positive P300 components of visual evoked potentials recorded at symmetric points of the frontal, parietal, temporal, and occipital areas of the right and left hemispheres of the cerebral cortex has been performed in subjects with or without the skill of operating a computer. Subjects inexperienced in an operator’s work exhibited an interhemispheric difference in the time and amplitude characteristics of the studied components. In subjects that had the skill of operating a computer, the interhemispheric difference was little, which suggests that the cortex plays only a small role in the cerebral control of this activity.     

Handedness in the common marmoset (Callithrix jacchus)

For about 20 months the development of hand preferences in 21 experimentally naive common marmosets (Callithrix jacchus) was examined in 15 different tests. Test preferences were compared with their spontaneous behavior preferences in such contexts as feeding, grooming, play, and others. In the spontaneous use of the hands, only eight animals showed a significant lateral preference (2 left-handed, 6 right-handed). During the test period, however, the number of handed marmosets increased to 19 (5 left-handed, 14 right-handed). Most of the animals fluctuated considerably in their preference levels, a situation which led to a remarkable test response inconsistency of handedness. When the test situation was changed, complete reversals of handedness were more frequent than weakening or strengthening of a particular preference. The animals' emotions during the test session and environmental variables affected handedness significantly. None of the tested marmosets showed an increase of hand preference from the first to the last test. Our results indicate that Callithrix is ambidextrous rather than handed.     

Spectral-correlation characteristics of the electrical activity of the brain of the rabbit in a state of calm wakefulness

Inter- and intrahemispheric relations of electrical activity of the pre-motor, sensorimotor (representation of forelimb and blinking) and visual zones of rabbit's cerebral cortex in calm alertness was studied by method of spectral-correlative analysis. Mean coherence levels of the EEG of tested hemispheric symmetric points and symmetric pairs of leads in the left and right hemispheres were characterized by a high temporal stability in the state of calm alertness and during sensory stimulation. A comparison of mean coherence values of EEG in symmetric leads, revealed a tendency to left-side dominance of statistical bonds of electrical processes. A tendency was shown towards interhemispheric asymmetry by mean parameters of EEG power spectra: the left hemisphere of the rabbit is characterized by a lower mean frequency of electrical activity and a more narrow effective frequency of the spectrum.