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.

[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 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.

[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.

[Oscillatory evoked potentials in the rabbit visual system during experimental retinal pathology induced by administration of monoiodoacetic acid]. / Ostsilliatornye vyzvannye potentsialy v zritel'noi sisteme krolika pri éksperimental'noi patologii setchatki, sozdannoi vvedeniem monoïoduksusnoi kisloty.

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.

[Function of the superior colliculi of the corpora quadrigemina during creation of a local focus of increased excitability in the mesencephalic reticular formation and sensomotor cortex]. / Funktsiia verkhnikh bugrov chetverokholmiia pri sozdanii lokal'nogo ochaga povyshennoi vozbudimosti v mezentsefalicheskoi retikuliarnoi formatsii i sensomotornoi kore.

In chronic experiments on waking rabbits, the foci of heightened excitability in the sensorimotor cortex and mesencephalic reticular formation affected in a similar way the background neuronal activity in the superior colliculi and that evoked by light stimuli. The effect was manifested in elimination of inhibitory pauses in the neuronal response to light stimulus and in a general increase of discharge frequency. Similarity of the cortical and reticular influences is due to their possible mediation by the same collicular interneurones participating in inhibitory pauses formation in the process of backward inhibition. Increased neuronal activity in the superior colliculi under the action of local foci in the sensorimotor cortex and mesencephalic reticular formation correlated with appearance of forelimb motor reaction to isolated light stimulus testifying to a formation of a functional connection between the visual and motor analyzers. Possible role of the superior colliculi in this process and their participation in the formation of a visually controlled reaction is discussed.