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Biomedical subjects

E V Kharitonov

Publications and source records attributed to E V Kharitonov.

At least 19 recordsLinked to original sources
PubMed1994

[The intrahemispheric contrast in transcallosal responses and its interhemispheric asymmetry in animals of both sexes].

A certain dynamics of changes in intrahemisphere contrast was revealed in the process of development of the transcallosal response: in the beginning of the response the right hemisphere is more focal, then the left one and afterwards again the right hemisphere. In males, the main changes of focality are related to the left hemisphere whereas in females--to the right one. The focality of a greater value is characteristic of the males' transcallosal responses whereas the distribution of the EPs is more diffuse in females. A specifics of the contrast gradient dynamics is described for the projection and associative cortical areas. A zonal specifics of the intrahemisphere contrast was shown in animals of different sex.

Animals↗
PubMed1994

[The asymmetry of parietal-visual and parietal-auditory transcallosal potentials and their sex dimorphism].

"Reverse" transcallosal responses (TCR) occurring in the visual and auditory cortex during stimulation of the temporal associative cortex of opposite hemisphere, were studied. The right hemisphere was shown to domineer in females, whereas a greater latency of the temporal-visual positive-negative TCRs was found in the males' right hemisphere and the females' left one. These and other data obtained suggest a greater lateralisation of the brain in males.

Animals↗
PubMed1993

[The role of transcallosal responses with an initial negativity in the formation of a pattern of interhemispheric asymmetry].

Negative-positive transcallosal homotopic responses (THR) occurred 2 times less frequently than the positive-negative ones in male cats, whereas the same ratio was 1:3 in female cats. The foci of maximal activity of the 1st and 2nd types THR did not coincide. The 2nd type THR were shown to have a lesser number of interzonal interconnections than in the case of the positive-negative potentials. A probable role of the negative-positive THR in limitation, contrasting of the increased excitability focus as well as the specifics of contraphasic THRs interaction in respect to the sex of animals, is discussed.

Animals↗
PubMed1992

[The effect of pregnancy on transcallosal evoked potentials].

Pregnancy induced an intrahemispheric redistribution of transcallosal flows mainly in the projection areas of the cat cortex. Functional interhemispheric asymmetry (FIA) of transcallosal evoked responses (TEPs) was determined by interhemispheric distribution of negative-positive responses in non-pregnant cats, whereas in pregnant ones it was determined by the asymmetry of positive-negative TEPs. The right hemisphere played the major part in the changes of the TEPs' amplitude parameters, and the left one--in temporal parameters.

Animals↗
PubMed1991

[The pattern of the interhemispheric asymmetry of transcallosal evoked potentials in a complex study of the projection and associative cortical areas].

In 38 anesthetized cats, homotopic transcallosal responses (TCR) were studied in somatosensory, visual, auditory, sensomotor and temporal areas. The TCR were found to be functionally asymmetrical. Some specific features of the TCR asymmetry were revealed in males and females. The asymmetry was of the same direction in sensomotor and somatosensory, visual and temporal areas, whereas it was opposite in its direction in visual and auditory areas. The changes of the TCR asymmetry seem to be due to formation of a new system of functional interzonal intra- and interhemispheric connexions.

Animals↗
PubMed1991

[Sex differences in the penetrance and expressivity of interhemispheric asymmetry].

In 38 anesthetised cat of both sexes, homotopic transcallosal responses (HTR) were studied in somatosensory, visual, auditory and temporal cortex of the brain. High penetration in cases of interhemispheric asymmetry was more specific for males and found mostly in cortical projection areas. For the functional interhemispheric asymmetry of the HTR amplitude-temporal parameters a high degree of expressiveness was characteristic in female cats. Possible reasons of these phenomena are discussed.

Animals↗
PubMed1989

Functional organization of interzonal transcallosal connections in the sensorimotor cortex.

Transcallosal evoked potentials (EP) in cat sensorimotor cortex, arising in response to stimulation of the visual or auditory zone of an opposite hemisphere, were investigated. Interzonal transcallosal responses (TCR) were shown to be present along the entire surface of the sensorimotor cortex. Videomotor EPs were mainly in the form of responses with initial negativity. The latent periods of audiomotor EPs were longer than those of videomotor EPs. Negative-positive videomotor responses had greater amplitudes as compared to the amplitudes of synphasic or audiomotor EPs. Responses with initial positivity, on the contrary, had greater amplitudes during Field AI stimulation than they had during the stimulation of Field 19. Interzonal transcallosal responses in MI zone were characterized by interhemispheric asymmetry. In a per-pair comparison of the amplitudes of response components, individual asymmetry was revealed for videomotor EPs. Audiomotor responses in the majority of investigated animals were of greater magnitude in the left hemisphere. The left hemisphere dominance for audiomotor EPs was mainly observed in females, whereas in males the asymmetry revealed was individual. It is suggested that the peculiarities of the interhemispheric asymmetry of interzonal audio- and videomotor functional transcallosal connections are determined by specificity of the intrazonal asymmetry of transcallosal streams in projection and association cortical areas.

Animals↗
PubMed1989

Interhemispheric interzonal connections in the parietal cortex.

In acute experiments on cats immobilized by tubarine transcallosal responses (TCRs) to the stimulation of the visual or auditory cortex of the opposite hemisphere were investigated in the parietal associative region. It was found that interzonal heterotopical TCRs could be recorded along the entire surface of the parietal cortex and were in two forms: positive-negative or negative-positive. Positive-negative evoked potentials (EPs) had greater latent periods. Negative-positive TCRs disappeared after the corpus callosum section or after the section of intracortical pathways on the side of recording and/or stimulation. EPs with initial positivity changed insignificantly as a result of these operations. Interzonal TCRs were characterized by the presence of interhemispheric asymmetry. The amplitude of early components in visual-parietal EPs of any configuration appeared to be greater in the right hemisphere. These responses also had a greater latent period. According to the magnitude of the late positive wave in visual-parietal TCRs the left hemisphere appeared to be dominant. Interhemispheric asymmetry in audioparietal EPs was individual. The amplitude of the early positive component prevailed as to magnitude in the right hemisphere in males and in the left hemisphere in females. The late negative wave in animals of either sex was greater in the right hemisphere. The peculiarities of generation and interhemispheric asymmetry of different components in visual-parietal and audioparietal TCRs are discussed. A symmetricising function of the parietal associative cortex is suggested.

Animals↗
PubMed1989

[Interzonal transcallosal connections of the sensomotor cortex].

Interzonal transcallosal EPs occurring in response to stimulation of visual or auditory cortex of opposite hemisphere, were recorded in the cat sensomotor cortex. Visual-motor EPs had mainly an initial positivity whereas audio-motor those were mainly initially negative. Latencies of the former EPs were longer. Negative--positive visual-motor EPs had a greater amplitude than their synphasic audio-motor ones. Initially positive EPs had a greater amplitude in stimulation of A1 rather than 19. The EPs revealed an interhemisphere asymmetry: audio-motor those were greater in the left hemisphere mainly in females. The specifics of the asymmetry seems to be due to an interzonal asymmetry of transcallosal flows of projectional and associative cortical areas.

Animals↗
PubMed1988

[Interregional transcallosal connections between the auditory and parietal cortex].

Interregional transcallosal responses to the stimulation of auditory cortex occurred throughout the surface of parietal cortex in immobilized cats and were either positive-negative or negative-positive. The former EPs had a longer latency and a greater total amplitude of both components. The negative-positive EPs disappeared after section of the callosal body whereas the positive-negative EPs were but insignificantly altered. The potentials were characterized by a functional interhemisphere asymmetry. The right hemisphere dominated by the average amplitude of the negative phase of negative-positive responses. The amplitude of early positive component dominated over the right hemisphere in males and over the left one in females. Delayed negative wave was greater over the right hemisphere in both sexes. The delayed components of the EPs had a significantly shorter latency of the peak in the dominating hemisphere.

Animals↗
PubMed1984

[Asymmetry of the interaction of transcallosal and thalamocortical flows in the sensorimotor cortex].

The interaction between transcallosal potentials and responses to stimulation of the contralateral sciatic nerve was studied in symmetrical areas of the cat sensorimotor cortex. The interacting responses and the resulting EPs were characterized by a functional interhemisphere asymmetry of an individual form. In transcallosal conditioning with 10-ms interstimuli intervals, the positive components of the EPs prevailed in the left hemisphere. The characteristics of the interhemisphere asymmetry were determined by the animal sex: the spatial--temporal interaction of the flows had different features in different hemispheres, was characterized by unequal markedness of asymmetry of the EP components as well as by opposite character of the asymmetry in animals of different sex. The characteristics of the EP interhemisphere asymmetry seem to be determined by an interaction of dominant foci occurring under these conditions in each of the hemispheres.

Animals↗
PubMed1984

[Characteristics of the transcallosal potentials in the parietal cortex of the cat].

Comparative study of the transcallosal EPs in the cat parietal and sensomotor cortical areas revealed that the parietal EPs were less stable and more uniform than the sensomotor ones. Distribution of the EPs over the sensomotor cortex's surface is more regular as compared with the parietal area. Focus of the transcallosal EPs maximal activity coincided usually with the parietal point symmetrical to stimulation. An individual form of functional interhemisphere asymmetry was revealed for the parietal cortical potentials. An inversion of positive-negative transcallosal EPs was shown to exist in the parietal area's IV layer. The data obtained seem to corroborate the opinion of different functional purposes of the areas under study which can be revealed by the interhemisphere interaction between these areas as well.

Animals↗
PubMed1982

[Spatial organization of the interaction between transcallosal and thalamocortical flows of excitation].

In 10 immobilized cats, the interaction between transcallosal potentials and responses to stimulation of the n. ischiadicus was studied in 85 points of the sensomotor cortex. The interaction effect of these responses is determined by their configuration in a given point as well as by time interval between them. The interaction has an obvious spatial-temporal character. Facilitating influences localized mainly in the area of overlapping of EP focuses whereas peripheral areas of the cortex were under a greater depressing effect of the transcallosal flow. The intermediate areas were subject alternately to facilitating and depressing influences. The above effects of interaction seem to reveal a modulating function of transcallosal flow which actualizes the concentration and contrasting of the excitation spreading over ascending projections.

Animals↗
PubMed1979

[Interaction of callosal and extracallosal systems].

Studies of the topography of homotopic transcommissural evoked potentials in 85 symmetrical points of the cat motor cortex, prior to and after section of the corpus callosum, revealed the functional areas as follows: acommissural (53% of the total area), purely callosal (23%), mixed (22%), and purely extracallosal (2%). The summation and reciprocal interrelationships between the callosal and extracion flows spreading over the extracallosal system.

Animals↗
PubMed1979

[Common pathway principle in the organization of callosal connections].

The direct cortical responses and transcallosal potentials were recorded in 170 symmetrical points of the cat motor cortex during the electrical stimulation of one hemisphere. The area of the direct responses was larger than that of transcallosal responses. The latter was concentrated in the center of the motor area, while the direct responses were located in peripheral areas. Thresholds for the direct responses were lower than those for the transcallosal responses. Variation of the strength of the stimulation led to the changes of localization of the EPs in both hemispheres. Callosotomy abolished or decreased the transcallosal potentials and increased or decreased the direct cortical potentials. This suggests the principle of the common pathway for the callosal system activity.

Animals↗
PubMed1978

[Asymmetric nature of a focus of maximal activity of transcallosal responses].

In immobilized cats, transcollosal (TCR) and direct cortical responses (DCR) from 170 points of the motor cortex, were recorded. The TCR maximal activity focus (MAF) is shifted in relation to the point symmetrical to stimulation (PSS) in oral--caudal direction. Ablation of the cortex around the stimulating electrode is followed by disappearance of TCR in MAF and of PSS and DCR beyond the ablation limits. Ablation of PSS entails diminishing of TCR in MAF. Transection of the corpus callosum eliminates TCR in MAF and PSS. The MAF shift seems to be due to a relatively strengthened convergence of several excitation flows in PSS, the flows spreading over the callosal fibers and intrahemisphere projections of both hemispheres.

Animals↗
PubMed1975

[Variability of neuronal activity of the parastriate cortex before and after callosotomy].

In acute experiments on anesthetized cats, variability of the unit activity in the field 18 of the visual cortex was studied. Both the spontaneous activity and the evoked activity by series of different light stimuli, were analysed. The data obtained show that callosotomy does not affect the variability of the spontaneous unit activity in the parastriate cortex. However, it does decrease the variability of the unit activity qualitative response (excitation--inhibition) to stimulation. The callosotomy increases variability of the predominant input (either ipsi--or contralateral) in regard to the mean spontaneous activity prior to and after a series of stimuli and decreases it in regard to the mean spontaneous unit activity for the whole period of study.

Animals↗