The authors present the results of a study of the effectiveness of EHF radiation on the cerebral hemodynamics, bioelectrical activity of the cerebral cortex, and functional state of the vestibular analyzer in chronic studies of cats using a model of vascular-vestibular dysfunction. The clinical part of the work reflects the results of studies of the functional state of cerebral blood circulation and the vestibular analyzer during the EHF treatment of angiovertebrogenic vestibular dysfunction in a background of initial manifestations of cerebral blood supply deficiency (angiodistonic variant).

Changes in the induced-potential components with direct EHF action on the cerebral cortex are shown in experiments with cats.

In chronic experiments on 6 cats the influence was studied of unilateral vestibular neurotomy on conditioned, oculographic and electrocardiographic reactions. In operated animals appeared sharply expressed posetonic and oculomotor disturbances, lowered general functional brain state, what was manifested in an increase of specific weight of slow spindle-shaped rhythmics and lowering of the conditioned activity level. Against the background of the lowered functional brain state interhemispheric asymmetry developed with relative predominance of the contralateral hemisphere, what was reflected in electrocorticographic manifestations and disturbance of conditioned spatial differentiations. Significance is grounded of the appearing interhemispheric asymmetry in the development of disturbances of spatial analysis in operated animals.

In chronic experiments on 6 cats the influence was studied of unilateral vestibular neurotomy on conditioned, oculographic and electrocardiographic reactions. In operated animals appeared sharply expressed posetonic and oculomotor disturbances, lowered general functional brain state, what was manifested in an increase of specific weight of slow spindle-shaped rhythmics and lowering of the conditioned activity level. Against the background of the lowered functional brain state interhemispheric asymmetry developed with relative predominance of the contralateral hemisphere, what was reflected in electrocorticographic manifestations and disturbance of conditioned spatial differentiations. Significance is grounded of the appearing interhemispheric asymmetry in the development of disturbances of spatial analysis in operated animals.

Unilateral injury to the brachium of the inferior colliculus resulted in a disturbance of the adequate perception of space, which was indicated by the unidirectionality of orientational and conditioned-reflex responses (in the same direction as the side of injury) to stimuli of various sensory modalities.

The ability for spatial analysis of stimuli of various sensory modalities was studied in cats with a unilateral section of the brachia of the posterior colliculi. To study the possible mechanisms of compensation of localization function in different periods following the brachia section, cortical evoked potentials to sound and light were recorded, and various areas of the neocortex removed (the temporal, parietal or sensorimotor). It was suggested that after a unilateral section of the brachia, compensation of localization of non-acoustic stimuli is linked with the recovery of interhemispheric functional symmetry within the corresponding analyser systems; localization of sound stimuli is restored primarily due to activation of the temporal neocortex in the intact hemisphere, i.e. involvement of one-hemisphere binaural mechanism.

In experiments on 13 cats a unilateral section of the brachii of inferior colliculi produced a stable interhemispheric asymmetry not only in the auditory system, but in other (vestibular, visual, somatic, olfactory) analysers as well, which led to a disturbance of adequate space perception. This was manifested in orienting reactions directed only to the side of brain lesion. Animals were no more able to distinguish between the right and left troughs either by spatial or by modal cues. A complete "disregard" by the animals of the trough contralateral to the side of lesion suggests a hemispheric lateralization of conditioned connections providing for an adequate direction of the animals' running.

The role of the neocortex temporal areas in the closing function was studied in chronic experiments on cats in the norm and after section of the posterior colliculi brachia. The techniques of functional elimination of the temporal neocortex by cold and section of the posterior colliculi brachia were used. Functional elimination of the cortical temporal areas prevents formation of a stable conditioned reflex in the first twenty sessions with cooling. Conditioned reflexes elaborated after section of the posterior colliculi brachia are not manifested in the case of cooling of the temporal areas throughout the period of observation (18 sessions). At the same time the conditioned reflexes elaborated before the section, are restored quite rapidly (five to six sessions). Hence, the neocortex temporal areas are more important for setting up conditioned connections than for their preservation and the use of connections previously elaborated.

Evoked potentials to acoustic stimuli were recorded in the temporal cortical area, the medial geniculate body and the posterior lateral thalamic nucleus in acute experiments on anaesthetized cats. Section of the brachia of the inferior colliculi in an acute experiment resulted in the disappearance of potentials in the examined structures. A distinct correlation has been revealed between the recovery of evoked potentials in the cortico-thalamic auditory structures (in four to six weeks) and the possible elaboration of conditioned reactions within this time period after lesion of the inferior colliculi brachia. The involvement of the temporal area in the general brain activity appears to be one of the major conditions for the formation of new conditioned connections. Possible ways of restoration of afferent input to the temporal cortical area after lesion of the inferior colliculi brachia are discussed.

Injury to the inferior colliculi causes considerable weakening or even total disappearance of the motor component of the orienting reflex. Other investigated components (electroencephalographic, cardiac, respiratory, psychogalvanic) remain unchanged. Manifestation of the components of the orienting reflex to photic stimuli is identical in normal and experimental cats.

In cats in the first months after destruction of the inferior colliculi, general motor activity is depressed and orienting reactions to acoustic stimuli are, disturbed.