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Biomedical subjects

N A Gadzhieva

Publications and source records attributed to N A Gadzhieva.

At least 19 recordsLinked to original sources
PubMed1997

[The mechanism of interaction between the thalamic posterior lateral nucleus and the sensomotor cortex in rabbits].

The thalamic posterior lateral nucleus was shown to exert phasic and tonic effects on the function of sensomotor cortex: the former in the form of pulvinar-cortical responses, and the latter in the form of foci of increased or decreased excitability. The findings suggest an inhibitory tonic effect of the sensomotor cortex on neuronal network of the posterior lateral nucleus.

Animals↗
PubMed1995

[The effect of stimulation of the suprachiasmatic and supraoptic nuclei of the anterior hypothalamus on the evoked activity of the visual cortex in rabbits].

Stimulation of the hypothalamus' suprachiasmatic (SCH) and supraoptic (SO) nuclei induced short-latency hypothalamo-cortical responses in the visual cortex affecting the light-induced responses. Possible mechanisms of the differential effects of the stimulation upon different phases of the visual EPs, and participation of the RF in these mechanisms, are discussed. There seems to exist an interconnection between the hypothalamic and light stimuli in the visual cortex.

Animals↗
PubMed1992

[The influence of the anterior hypothalamus on the electrical activity of the retina].

Single stimuli applied to the suprachiasmatic and supraoptic nuclei of the hypothalamus evoked short-latency hypothalamo-retinal responses which exert influences upon formation of the "a" and "b" waves of the electroretinogram, the changes of the waves being opposite by character. The effects from the suprachiasmatic and supraoptic levels were opposite, too.

Animals↗
PubMed1991

[The effect of impulse stimulation of the visual cortex on the function of the superior colliculus in the waking rabbit].

In alert rabbits, pulse stimulation of the visual cortex interfered with the formation of short latency responses in superior colliculus. The effect of visual cortex upon the superior colliculus function may have a phasic inhibitory character. Blockade of the RF adrenergic apparatus enhances the inhibitory effect, whereas stimulation of the RF by anodal current induces an opposite effect. The character of cortical influence upon the superior colliculus function seems to depend on initial functional state of cerebral unspecific systems.

Animals↗
PubMed1990

[The influence of the posterior hypothalamus on the visual cortex in different states of the reticular formation].

In alert rabbits, stimulation of posterior hypothalamus induced short-latency responses in the visual cortex and affected the formation of the EPs to light. Depending on the intervals between the stimuli, either initial extinction of the EPs (1-15 msec) or subsequent selective facilitation of its positive component with simultaneous depression of negative (20-100 msec) one, or complete recovery of the response (200-300 msec), were observed. Aminazine and benactizine made the effect of the posterior hypothalamic stimulation on visual EPs to light less obvious and changed its dynamics. Other findings suggested an inhibitory effect of the mesencephalic RF on the activity of hypothalamo-cortical input. A role of phasic mechanism of hypothalamic control in realization of visual cortex's perceptive function, is discussed.

Animals↗
PubMed1989

[The role of the posterior lateral thalamic nucleus in the rabbit in the mechanisms of information transmission in the visual cortex].

In chronic alert rabbits, both transient and sustained influence of the nucleus lateralis posterior upon visual cortical responses to the light flashes, were shown. The transient influences were revealed by an increase of the responses amplitude in the nucleus lateralis posterior and by a decrease of the amplitude during the K depression. The sustained influences took part in forming of thalamo-cortical responses in visual cortex. This reciprocity was particularly obvious during pulse stimulation of the nucleus lateralis posterior. The sustained influences were more significant than the transient ones.

Animals↗
PubMed1989

[Control of conduction of afferent impulses across the lateral geniculate body by the side of the superior colliculus in alert rabbits].

On alert rabbits it was shown that the stimulation of the superior colliculus inhibit visual evoked potential both of the ipsi- and contralateral geniculate body. Besides, the suppression of amplitude of the contralateral geniculate body's evoked potential was more significant than amplitude of the ipsilateral geniculate body's evoked potential. On the basis of the obtained results the authors suppose that superior colliculus is involved in organization of the effect of saccadic suppression of lateral geniculate body's visual responses.

Animals↗
PubMed1987

[Formation of slow background activity in different parts of the visual analyzer following section of half the tectum mesencephali].

Significant changes in the formation of electrical activity rhythms have been revealed in the lateral geniculate body, superior colliculus and visual cortex during section of one half of midbrain operculum in cats anesthetized with nembutal. It was determined that all changes in slow activity generation in the lateral geniculate body, superior colliculus are reflected in changes in the formation of electrical activity of the visual cortex. It is suggested that lateral geniculate body and superior colliculus may be involved in the generation of some electrical activity rhythms of the visual cortex.

Animals↗
PubMed1987

[Effect of visual cortex stimulation on lipid peroxidation in the rabbit retina].

Chronic experiments on rabbits have shown that visual cortex stimulation resulted in intensified lipid peroxidation in the retina with the parallel decrease of electroretinogram amplitude parameters. The transsection of the optic nerve resulting in the elimination of retinal corticofugal inputs diminished the accumulation of lipid peroxidation products in the rabbit retina during light adaptation. Preliminary insertion of antioxidants to animals (vitamin E and ionol) prevents the inhibitory effect of the cortex on the function of the retina. The data obtained are discussed in view of possible involvement of lipid peroxidation in the retina into the realization of the regulating influence of the cortex on the function of the retina.

Animals↗
PubMed1985

[Oscillatory evoked potentials in the rabbit visual system during experimental retinal pathology induced by administration of monoiodoacetic acid].

ERG and EP of the visual cortex (VC) and superior colliculus (SC) were investigated under experimental dystrophy of the retina induced by intravenous injection of monoiodoacetic acid in different doses. The relative resistance of the VC to the derangement of retinal function was established. It was manifested by less marked suppression of its EP as compared with ERG. Taking into consideration the selective projection to the SC of the rod system that was damaged to a greater degree under pathology in question, it is suggested that functional suppression of the SC might facilitate the conduction of visual information through the main retino-geniculo-cortical canal. This might be one of the factors of VC resistance to the impairment of retinal function. This assumption was confirmed in experiments with SC electrocoagulation in which one could observe the facilitation of EP formation of the contralateral VC.

Animals↗
PubMed1983

[Characteristics of the evoked electrical reactions of the nucleus lateralis posterior in the rabbit thalamus and their dependence on cortical and reticular formation function].

The electrical responses of n. lateralis posterior of the thalamus (nLP) to light stimuli of different intensity were recorded in alert rabbits, and their interrelationships with the reactions of retina, superior colliculi and visual cortex were analysed. The retina rather than superior colliculi appeared to play a major role in afferent supply of nLP in rabbit. The organized mechanism of facilitating reticular control of the nLP function was shown, with the adrenoreactive mechanism playing the most important role in the reticular influence. The inhibitory influence of visual and sensomotor cortical areas upon neuronal mechanism of nLP forming the responses to photostimuli, was revealed. The effects of visual cortex were the most expressive and stable.

Animals↗
PubMed1983

[Relation of short-latency processes in the visual system of the rabbit to pre-excitation inhibition in the retina].

Low-amplitude early negative potential preceding the positive component of primary responses to light was observed in the optic tract, superior colliculus, lateral geniculate body and visual cortex in chronic experiments with special recording schedule in rabbits. The early negative potential proved to be genetically connected with the "a"-wave of the electroretinogram. During the suppression of all but the "a"-wave ERG components with glycine, the early negative potential alone is preserved in the central structures of the visual system.

Action Potentials↗
PubMed1977

[Oscillatory potentials in the structures of the visual system].

The electroretinogram oscillatory potentials have similar general configuration and frequencies. Under the conditions of experimental dystropia of the retina and also after glycine administration, suppression of the oscillatory potentials formation in retina is accompanied by suppression of the evoked responses formation in the LGB, superior colliculi, visual cortex, and chiasma. The oscillatory potentials in the cerebral structures are related to the primary complex of their evoked responses. The importance of using the oscillatory potentials to study the mechanism of influence of the visual stimuli on the evoked potentials, is discussed.

Animals↗
PubMed1975

[The relationship between oscillatory potentials of the electroretinogpam and components of the visual cortex evoked response].

In the electroretingram of rabbit, the oscillatory potentials (OPs) were shown to appear in response to a wide range of the light stimuli intensities (0.023--120 joules). The minimum time required for the OP onset was 10 msec. The OP duration was independent of the stimulus intensity and ranged between 6--7 msec. The number of OPs, their amplitudes, latency, and peak latency varied along with the intensity of the stimuli. OP1 occurred during developing of "a" wave, while OP2, OP3, OP4--at the ascending phase of "b" wave of the electroretinogram. The latency and the peak latency of the OP1 were always shorter than the respective parameters of the first component of evoked potential in the visual cortex. A definite time correlation between the formation of OP1 and OP2 and the first two components of the evoked potential was revealed. Interrelationship between OP3, OP4, and later components of evoked potentials in the visual cortex was much more complicated.

Animals↗
PubMedDate not supplied

Evoked electrical responses of nucleus lateralis posterior of the rabbit thalamus and their dependence upon the functional state of the cortex and reticular formation.

The electrical responses of the thalamic pulvinar (of its analogue, the nucleus lateralis posterior (nLP)) to light stimuli of various intensity were recorded in awake rabbits, and their interrelationships with the responses of the retina, superior colliculi, and visual cortex were analyzed. It is postulated that a major role in the afferent supply of the rabbit nLP belongs to the optic track and the superior colliculi. The presence was demonstrated of a highly organized analyzer of the reticular control of nLP function that is of a facilitatory character. The most important role in reticular influence belongs to its adrenoresponsive mechanism. An inhibitory influence was demonstrated for the visual and sensorimotor regions of the cerebral cortex on the nLP neuronal apparatus producing responses to light stimuli. The influence of the visual cortex are the most pronounced and stable.

Animals↗
PubMedDate not supplied

Association of short-latent processes in the rabbit visual system with pre-excitation inhibition in the retina.

An electrographic correlate of short-latent processes in the visual system corresponding to the ERG a-wave was detected in chronic experiments on awake rabbits. The formation of an early negative potential (ENP), small in amplitude, that precedes the positive component of the primary responses (PR) to light and is thus the earliest signal concerning the arrival of information from the retina was detected during a special recording regimen in the optic tract, superior colliculi, outer geniculate body, and visual cortex. The shift in the latent periods with respect to the onset of the development of the ERG a-wave comprised 2-3 msec in all the above structures. The suppression of all ERG components except the a-wave by glycine injected into the vitreous body was accompanied in all structures by the suppression of all PR components except the very initial ENR. Since the pre-excitatory inhibition of ganglionic elements corresponds to the ERG a-wave at the exit from the retina, the role of this inhibition in the transmission of information concerning the very first instant of the visual signal both to subcortical centers and the visual region of the cerebral cortex should be recognized.

Animals↗