Influence of pulse stimulation of the visual cortex on the function of the superior colliculus of the awake rabbit.

It has been demonstrated in awake rabbits that stimulation of the visual cortex by a solitary pulse of electrical current leads to the formation of a short-latency response in the superior colliculus. The formation of this response is suppressed when a light stimulus precedes it. At the same time, a conditioning solitary electrostimulation of the visual cortex induces a short inhibition of the formation of the response to the test light stimulus. This fact suggests that the influences of the visual cortex on the functioning of the superior colliculus may be biphasic in character. When the adrenergic apparatus of the reticular formation is blocked this inhibitory influence bears a more pronounced and prolonged character. The stimulation of the reticular formation, on the other hand, by means of anodic polarization leads to the diametrically opposite effect: the inhibitory character of the influence of the cortex is replaced by a facilitatory one. The inference is drawn that the character and the directionality of the influence of the visual cortex on the functioning of the superior colliculus is determined to a significant degree by the initial functional state of nonspecific brain systems.

[Interactions of the superior colliculus and the sensorimotor cortex in the alert rabbit]. / Vzaimootnosheniia verkhnego dvukholmiia i sensomotornoi kory u bodrstvuiushchego krolika.

The tonic increased influence of the superior colliculus (SC) on the formation of visual responses of the sensorimotor cortex (SMC) was shown on the alert rabbits. It was shown that SC influence was realized through tectothalamocortical (nucleus lateralis posterior) canal relation. It was established that SMC of the alert rabbits in its turn exerts the inhibitory phasic influence on SC function. The obtained data are discussed in the light of participation of the colliculo-cortical and cortico-collicular interactions in the organization of the visual-motor coordination necessary for realization of the visual controlled behaviour.

[Effect of cat motor cortex on the formation of lateral geniculate nucleus responses evoked by contralateral superior colliculus stimulation]. / Vliianie motornoi kory na formirovanie otvetov naruzhnogo kolenchatogo tela koshki, vyzvannykh stimuliatsiei kontralateral'nogo verkhnego dvukholmiia.

It was shown in experiments on anesthetized cats that motor cortex (MC) stimulated by single current pulse caused formation of the lateral geniculate nucleus (LGN) response. It was established that changes in formation of LGN response evoked by contralateral superior colliculus (SC) stimulation were observed by condition of the precedence of LGN response evoked by stimulation of the MC. The expressiveness level of that decrease depended on intervals between conditioning cortical and testing tectal stimuli. At the same time the stimulation of the MC by single current pulse caused no changes in formation of the visual evoked potential of LGN. However, a significant decrease of the visual response of that part of the SC which stimulation caused formation of the LGN response was observed under the same conditions. The obtained data permit supposing that MC checks realization of the tectal influences on the LGN function on the tectal level. It is assumed that realization of the effect of the saccadic suppression of the LGN function in which accomplishment, as it was supposed earlier, the SC took part, was controlled by the MC phasic influence.

[The effect of impulse stimulation of the visual cortex on the function of the superior colliculus in the waking rabbit]. / Vliianie impul'snoi stimuliatsii zritel'noi kory na funktsiiu verkhnego dvukholmiia bodrstvuiushchego krolika.

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.

[The effect of the superior colliculus on the function of the contralateral lateral geniculate body in the cat]. / Vliianie verkhnego dvukholmiia na funktsiiu kontralateral'nogo naruzhnogo kolenchatogo tela koshki.

In acute experiments on rats it was shown that stimulation of the superior colliculus [correction of upper bimounding] leads to the formation in the contralateral lateral geniculate [correction of external geniculated] body of a colliculus-geniculate response. The nature of the changes in a considerable degree is determined by the fact, to which neurones of the lateral geniculate [correction of external geniculated] body, the effect of contralateral superior colliculus [correction of upper bimounding] is addressed.

[The effect of stimulation of the ocular muscles on the formation of visual responses in the cat lateral geniculate body]. / Vliianie stimuliatsii glaznykh myshts na formirovanie zritel'nykh otvetov naruzhnogo kolenchatogo tela koshki.

It has been shown in acute experiments on anesthetized cats that stimulation of the ocular muscles by single current pulse caused different changes in formation of negative and positive components of the visual response of the lateral geniculate nucleus. It was established that character of those changes depended on the interval between conditioned muscular and tested light stimuli.

Role of the posterolateral nucleus of the thalamus in mechanism of information transmission to the visual cortex.

It has been demonstrated in chronic experiments on wakeful rabbits that the posterolateral nucleus of the thalamus exerts tonic and phasic facilitatory influences on the formation of responses of the visual cortex elicited by a light flash. The tonic influences were expressed in an increase in the amplitude parameters of the responses of the visual cortex in conditions of the formation in the posterolateral nucleus of the thalamus of a focus of heightened excitability (anode polarization), and their perceptible diminution with potassium depression in this nucleus. The phasic influences were expressed in the formation in the visual cortex of thalamocortical responses elicited by pulse stimulation of the posterolateral nucleus of the thalamus, which displayed a close interaction with the responses of the cortex elicited by the light flash. This interaction consisted in a noticeable facilitation of the responses of the visual cortex against the background of a conditioning pulse stimulation of the posterolateral nucleus. The facilitatory effect of the phasic influences was more significant than the effect of the tonic influence.

[The possible mechanism of the saccadic suppression of the superior colliculus function in the rabbit]. / Vozmozhnyi mekhanizm sakkadicheskogo podavleniia funktsii verknego dvukholmiia krolika.

Experiments with alert rabbits have shown that simulation of deep layers of superior colliculus (SC) significantly inhibit visual responses of contralateral SC surface layers. These data are discussed in the light of the SC participation in organization of the saccadic suppression of the contralateral SC function.

[Control of conduction of afferent impulses across the lateral geniculate body by the side of the superior colliculus in alert rabbits]. / Kontrol' provedeniia afferentnoi impul'satsii cherez naruzhnoe kolenchatoe telo bodrstvuiushchego krolika so storony verkhnikh bugrov chetverokholmiia.

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.

[The role of the posterior lateral thalamic nucleus in the rabbit in the mechanisms of information transmission in the visual cortex]. / Rol' zadnego lateral'nogo iadra talamusa krolika v mekhanizme peredachi informatsii v zritel'nuiu koru.

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.

[Participation of the thalamic reticular nucleus in the shaping of the interrelations of the mesencephalic reticular formation and the lateral geniculate body]. / Uchastie retikuliarnogo iadra tamalusa v formirovanii vzaimootnoshenii mezéntsefalicheskoi retikuliarnoi formatsii i naruzhnogo kolenchatogo tela.

On the awake rabbits and cats under nembutal anesthesia it has been shown that the reticular nucleus of the thalamus takes considerable part in the formation of reticulogeniculate response of the lateral geniculate body (LGB) to electrostimulation of the mesencephalic reticular formation. It is assumed that the reticular nucleus of the thalamus takes basic part in a realization of "rapid" physical influences of the reticular formation on the LGB.

[Formation of slow background activity in different parts of the visual analyzer following section of half the tectum mesencephali]. / Formirovanie medlennoi fonovoi aktivnosti razlichnykh otdelov zritel'nogo analizatora pri pererezke poloviny pokryshki srednego mozga.

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.

[Effect of visual cortex stimulation on lipid peroxidation in the rabbit retina]. / Vliianie stimuliatsii zritel'noi kory na perekisnoe okislenie lipidov v setchatke krolika.

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.

[Effect of deafferentation of the lateral geniculate body on its background activity]. / Vliianie deafferentatsii naruzhnogo kolenchatogo tela na ego fonovuiu aktivnost'.

Elimination of reticular inputs to the lateral geniculate body (LGB) by sectioning of one half of the midbrain operculum, did not affect significantly the characteristics of the LGB evoked potential to light stimulus. At the same time LGB response to stimulation of the reticular formation by a single current impulse, though did not disappear completely, but changed greatly: its latency became twice as long, the negative component of the response was no more recorded. In conditions of LGB deafferentation, the characteristics of all rhythms of its electrical activity, besides the alpha-like one, considerably changed. At the same time, exactly this last rhythm underwent the greatest changes on the EEG of the visual cortex. On the basis of the obtained data it is suggested that the reticular formation takes a considerable and multiple part in generation of LGB rhythmic activity and that changes in its characteristics are clearly reflected in the ECoG rhythms formation. Retention of the LGB visual evoked potential and of the response to stimulation of the reticular formation after the section of one half of the midbrain operculum testifies to the presence of several reticular inputs to LGB.