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Biomedical subjects

V A Fedan

Publications and source records attributed to V A Fedan.

At least 19 recordsLinked to original sources
PubMed1989

[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.

Activins↗
PubMed1987

[Reflection of the magnitude of the arm rotation angle by the time parameters of kinesthetic evoked cortical potentials in rhesus macaques].

The electrophysiological experiments were carried out on five male macaques rhesus under nembutal anesthesia. Kinesthetic evoked potentials in response to arm rotation in the elbow joint were registered in the contralateral primary somatosensory cortex. The data obtained show a significant increase in the duration of kinesthetic potential first positive component with 10 degrees-40 degrees arm rotation amplitude, as compared to 2 degrees rotation. On the contrary, the latent period and amplitude of the component in this stimulation range (2 degrees-40 degrees) were similar. It is suggested that the increase in the arm rotation angle is selectively reflected in the temporary parameters of kinesthetic potential first positive component.

Animals↗
PubMed1986

[Changes in the structure of group behavior in callosotomized rhesus monkeys].

The studies were performed on 4 intact and 3 callosotomized adult male rhesus monkeys that comprised one social group. Group behaviour of all the monkeys was investigated by the frequency method of social contacts registration. Both aggressive and friendly contacts were registered. The results obtained have shown a considerable decrease in social contacts of callosotomized rhesus monkeys, as compared to normal animals. The aggressive contacts prevailed in the behaviour of the operated monkeys. The data suggest that callosotomy does not only significantly decrease the frequency, but also alters the structure of social contacts in the rhesus monkeys.

Aggression↗
PubMed1985

[Role of the neocortical and subcortical commissures in the interhemispheric transfer of visual information to the hippocampus].

The light flash evoked potentials were recorded in the hippocamp of cats with transected left optic tract and cerebral commissures. The data obtained show a significant reduction in the response amplitude (by 1.5-2 times) in both hemispheres after unilateral transection of the optic tract. The minimal response amplitude (10-15 times less than normal) was recorded in the left hippocamp of cats with additional transection of the commissures of the endbrain, mesencephalon and diencephalon. In contrast, the latent period of the first and second components of the evoked potential was similar to that in the control group animals. It is suggested that the neocortical commissural visual inputs play the most important role in interhemispheric transmission of visual information to the hippocamp.

Animals↗
PubMed1985

[Geniculate relay of interhemispherical transmission of visual information].

Electrophysiological experiments were made on conscious cats with different degree of dissection of the classical and commissural optic tracts to the lateral geniculate body. The data obtained indicated that dissection of the direct retinal tracts to the lateral geniculate body (unilateral dissection of the optic tract) leads merely to the reduction in the amplitude of evoked potentials in response to light flashes. However, the latent period of the first component of the response in this structure appeared the same as in intact animals. Comparison of these data with those obtained in analogous experiments made on the visual cortex allows the conclusion that the geniculate body is the main subcortical relay of the visual commissural effects which are transmitted from the retina to the cortical regions of the brain.

Animals↗
PubMed1985

[Role of the commissural channels of the somatosensory system in the conduction of feedback signals during the control of voluntary movements].

The time-course of formation of the conditioned defence reflex and electromyograms of the working forelimb were studied on cats with classical and commissural somatosensory pathways transections. It was established that exclusion of the classical somatosensory projections only reduces the rate of the skill formation that is related to the possibility of conducting feedback signals via the remaining commissural pathways. However, the commissural channel in question is not effective enough, since its isolated functioning is accompanied by an increase in the duration of instrumental movement. The combined transection of the classical and commissural somatosensory pathways excludes the possibility of formation of the conditioned reflex on the "deafferented" limb. The lack of direct visual control over the moving forelimb does not essentially affect the behavioral and electromyographic data.

Animals↗
PubMed1985

[Functional organization of the kinesthetic projections of the 1st somatosensory region of the cat cortex].

Electrophysiological studies were performed on adult cats under ethaminal anesthesia. Kinesthetic potentials were evoked by passive extension of the ulnar joint and recorded in contralateral primary somatosensory cortical area. Natural (nonelectrical) stimulation of peripheral kinesthetic receptors was performed according to the author's original method. The results obtained show significantly shorter latent period of contralateral kinesthetic potentials in comparison with somatosensory potentials in response to electrical stimulation of the skin. These data demonstrate the possibility of super-rapid conduction of modal-specific volleys to the cortical projection centres in the kinesthetic system of cats.

Animals↗
PubMed1984

[Extracallosal channels of interhemispheric transmission of visual information].

Evoked potentials (EP) in response to light flashes were recorded in cats with different degree of optical tract disconnection. In intact and operated on animals, the latent period of the first component of these EP was the same as in the visual cortex. The different degree of disconnection of the classic and commissural optical tract brought about an increase in the amplitude of commissural potentials. The data obtained point to the existence of the effective callosal and extracallosal volleys of interhemispheric transmission of visual information, which are also likely to pay an essential part in compensatory processes of the optical system.

Animals↗
PubMed1984

[Centro-peripheral organization of the kinesthetic system studied by natural stimulation of peripheral receptors].

A method is suggested for investigation of the central peripheral organization of the kinesthetic system by nonartefact natural stimulation of the receptors in animals with the aid of a kinesthetic stimulator. The data obtained show the evoked potentials in response to natural stimulation in the contralateral somatosensory cortex of cats to have a significantly shorter latent periods as compared with electric stimulation. It is concluded that the rate of kinesthetic afferent volleys conduction in the somatosensory pathway is higher than that of mixed information during electric stimulation. The method suggested can be used both under experimental and clinical conditions.

Afferent Pathways↗
PubMed1984

[Compensation of anisocoria in cats following transection of the optic tract: the role of subcortical commissures].

Experiments were carried out on cats with unilateral optic tract transection and cerebral commissures. The data obtained indicate that destruction of the afferent part of the pupillary reflex by optic transection led to reversible anisocoria. In cats with combined transection of the optic tract and teleencephalic, diencephalic and mesencephalic commissures, such a rehabilitation did not occur. In contrast, section of telencephalic commissures alone was immaterial for the processes of compensation of papillary system function. The data obtained attest to an important role of subcortical commissures in compensation of anisocoria after destruction of the afferent arc of the papillary reflex to light.

Afferent Pathways↗
PubMed1984

[Interhemispheric transmission of visual information to the cat somatosensory cortex: role of subcortical commissures].

Experiments were made on adult cats with combined transection of the visual tract and brain commissures. One to 1.5 month after operation microelectrodes were implanted into the primary somatosensory cortex. Transection of the classical and commissural (with the exception of subventricular and mesencephalon reticular interhemispheric tracts) visual inputs to the somatosensory cortex resulted in a decrease of the number of neurons that responded to visual stimulation. Activation of such neurons was provoked by visual information conduction via two subcortical commissural communications: the third ventricular fundus and midbrain reticular formation.

Animals↗
PubMed1984

[Compensatory restoration of function in cats following resection of the somatosensory pathways: role of the cerebral commissures].

Experiments were carried out on cats with different transections of the classical somatosensory pathways and cerebral commissures. The data obtained demonstrate substantial restitution of somatosensory functions in animals after unilateral transection of the classical somatosensory pathways which were tested by neurological and behavioral methods. Cats with combined transection of the classical somatosensory pathways and telencephalic, diencephalic and mesencephalic commissures did not manifest any such rehabilitation. Exclusion of the direct visual control beyond the "deafferented" part of the body by optic tract transection is immaterial for these processes.

Animals↗
PubMed1984

[Commissural mechanisms of restoring visual functions].

The perimetric studies were carried out in adult cats with reduced classical and commissural visual pathways. The data obtained indicate substantial recovery of the temporal visual fields in cats with unilateral optic tract transection during one year after operation. The animals with combined optic tract and cerebral commissural transection did not demonstrate any remarkable restitution of visual fields. These findings allow the conclusion about the primary role of cerebral commissures in the compensatory mechanisms of visual functions after visual tract injury.

Animals↗