Topography of afferent and efferent flows in the mechanisms of auditory selective attention.

The auditory evoked potentials (AEP) were recorded in 10 healthy subjects under the conditions of simple rhythmic stimulation and in an attention task. The mid- (10-60 msec) and long-latency (up to 400 msec) AEP were analyzed by mapping the evoked potentials and by assessment of their spatial-temporal characteristics. It is hypothesized that the interaction of the parietal and left-sided temporal and frontal divisions exert an efferent influence on the brainstem structures in the 15-35 msec time segment. The amplitude of the P90 and P250 waves is reduced in the attention task. The amplitude of the late component P350 increases mainly in the central and anterior divisions of the brain.

[The topographic mapping of evoked bioelectrical activity and other methods for the functional neural visualization of the brain]. / Topograficheskoe kartirovanie vyzvannoi bioélektricheskoi aktivnosti i drugie metody funktsional'noi neirovizualizatsii mozga.

The paper is concerned with comparative characterization of brain functional imaging used in medicine today: bioelectrical activity mapping, assessment of spatial changes in cerebral blood flow by radionuclide and hydrogen clearance, NMR imaging, PET-scan, magnetoencephalography and thermoencephaloscopy. Original researches in neurosurgery clinic with the use of the mapping of evoked potentials enable the conclusion to be drawn about advisability of applying these methods in treatment and diagnostic practice. Besides, the mechanisms of compensation for higher mental functions in organic brain lesions are discussed.

[Methods for analyzing brain evoked potentials clinically and in psychophysiology]. / Metody analiza vyzvannykh potentsialov mozga v klinike i psikhofiziologii.

In the article one can find compare classification of excited brain potential analysis methods using for tasks of neurophysiology of man. Importance of visual data analysis, methods of multimeasure statistics and correlation analysis are discussed. Methods of dipoles localization and three-channel "lissa-djouson" trajectory are analysed from the position, that head is volume conductor. The last part of the article is devoted to importance of space methods of analysis of excited potentials, mainly for mapping of bio-electrical and magnetic exited potentials.

[The thalamic integration of afferent flows in man during image recognition]. / Talamicheskaia integratsiia afferentnykh potokov u cheloveka pri opoznanii obrazov.

The article deals with the mechanisms of interaction of afferent flows at intrathalamic and thalamocortical levels of integration in humans identifying visual, auditory and tactile images. As the methodic model of thalamic block we used patients of surgical clinic with topically diagnosed volume process of the region of the third ventricle. Psychophysiological tests and multichannel EPs recording revealed functional significance of thalamus in the processes of perception and also mechanisms of compensation of these functions in pathological process.

[The significance of emotional processes in man in the mechanisms of analyzing the effect of varying contrast stimulation]. / Znachenie émotsional'nykh protsessov u cheloveka v mekhanizmakh analiza vliianiia raznokontrastnoi stimuliatsii.

We estimated the role of emotional processes in regulation of the structural afferentation of varying contrast in healthy young subjects by means of VEP recording and investigation of Cattell factors (C and Q4). The amplitude of N70 in all the subjects and that of N150 in subjects with the high stress characteristics were in a direct ratio with the contrast of the stimuli. For the persons with the low stress characteristics an inverse ratio was observed in the occipital-parietal leads while in the frontal areas a switching-over control mechanism was manifested.

[The negative components of visual evoked potentials in the mechanisms of the classification of incomplete images]. / Negativnye komponenty zritel'nykh vyzvannykh potentsialov v mekhanizmakh klassifikatsii nepolnykh izobrazhenii.

Event-related brain potentials were recorded in 16 young adult subjects in response to a short presentation of recognizable and nonrecognizable visual images with an incomplete set of signs. Sequential brain maps and amplitude-temporal ERP parameters in 1000 ms poststimulus epoch were estimated (BMDP 4M and 7M, 1987). The results suggested that the component N450 was specifically related to a perception of nonrecognizable visual images. N70 and N150 reflected voluntary attention during invariant recognition and the late negative waves (600-1000 ms) reflected an "exhaustive search" for categorization of new information.

[Characteristics of the temporal resolution of signals in the visual analyzer in the rabbit]. / Kharakteristika vremennogo razresheniia signalov v zritel'nom analizatore krolika.

Biopotentials of the retina (ERG), optic tract, lateral geniculate body and visual cortex were recorded in response to repeated photostimulation within the range of 0.1 to 50 c/s and to paired flashes with an interval of 15 to 200 ms between them, to characterize summating and discriminating properties of the rabbit visual system in conditions of photopic and scotopic adaptation. A heterogeneity of studied structures was shown in their ability to temporal signals resolution, though quantitatively the differences were not great. It was found that in photopic conditions, with similar physiological intensity of the stimulus, temporal discrimination is much higher. The analysis of the experimental data showed that the ability to temporal resolution is due not so much to temporal summation processes, as to trace dynamics of excitability.

[Amplitude-temporal characteristics of evoked responses of the visual analyzer to stimuli of growing intensity]. / Amplitudno-vremennye kharakteristiki vyzvannykh otvetov zritel'nogo analizatora na stimuly vozrastaiushchei intensivosti.

A study was made on cats of the dependence of latency, peak latency, amplitudes and slopes of I and II phases of primary evoked potentials in the chiasm, the colliculi, the lateral geniculate body and visual cortex on the intensity of the photic stimulus in the range of intensities of II orders above the threshold. Practically in the whole examined range, the logarithmic connection is retained, testifying to the extremely wide possibility of the visual system to discriminate a signal in securing a reflex act.

[The topography of the afferent and efferent flows in the mechanisms of auditory selective attention]. / Topografiia afferentnykh i éfferentnykh potokov v mekhanizmakh slukhovogo selektivnogo vnimaniia.

Auditory evoked potentials (AEPs) were recorded in 10 adult healthy subjects under conditions of simple rhythmical stimulation and during solving selective attention task. Middle- (10-60 ms) and long-latency (up to 400 ms) AEPs were analysed by AEP mapping and by evaluation of their spatio-temporal characteristics. it is suggested that interaction between the parietal, left temporal and left frontal cortical areas exerts efferent influence to brainstem structures over a period of 15-35 ms. Amplitudes of P90 and P250 components were reduced during selective attention task. The late P350 component increases, mainly, in the central and frontal cortical areas.

[The characteristics of perceptive learning and memory in psychopathological states]. / Osobennosti pertseptivnogo obucheniia i pamiati pri psikhopatologicheskikh sostoianiiakh.

Dynamics is studied of visual images recognition in patients with schizophrenia under the influence of small doses of ionizing radiation used with therapeutic purpose. Functional state of the brain is evaluated by amplitude-temporal parameters of visual and auditory EPs. After conducted therapy no changes in responses to light flashes are found, and in auditory EPs in a part (the first group) of patients there is an increase of the component N1 amplitude in the frontal area. The same group is characterized by lower parameters of visual images recognition. Conclusion is made about the presence of non-specific changes of visual gnosis in patients with schizophrenia and about involvement of the associative frontal structures in pathologic process. Possible mechanisms of disturbance of the perceptive learning and memory processes in schizophrenia are discussed.

[Patterns of afferent signal convergence in the neurons of the frog midbrain tectum]. / Zakonomernosti konvergentsii afferentnykh signalov na neironakh kryshi srednego mozga liagushki.

The activity of 168 optic tectum units was recorded in conditions of separate and combined actions of light, sound, and pain stimuli. The sensitivity of the neurons to multisensory convergence depended on their spontaneous activity. Excitatory--inhibitory characteristics of responses to unspecific stimuli in most cases were similar to specific responses. Combined action of different stimuli complicated and increased the number of response types.

[Effect of flash on optokinetic nystagmus and postoptokinetic reactions]. / Vliianie fotovspyshki na optokineticheskii nistagm i postoptokineticheskie reaktsii.

Chronic experiments in rabbits revealed disturbances of visual function and the rate of restoration of detecting sensitivity to perception of movements after flash,--by means of the duration of the optokinetic nystagmus (OKN) absence and the period of the optokinetic (OK) responses restoration after the action of flash on the retina. Besides, the duration od the reverse postoptokinetic nystagmus (RPN) after the flash was determined in presence of illuminated OK--cylinder and the stripes in visual field, the latters being an object of fixation under normal conditions leading to cessation of the RPN. The RPN under these conditions lasted for 64.1 +/- 4.3 sec after the flash, switching off the light leading to reappearance of the RPN. The OKN, in spite of the OK stimulation, is absent after the flash during 118.0 +/- 8.4 sec and reaches its initial level within 175.2 +/- 21.7 sec starting from the first stimulus.

[Military occupational work capacity as a criterion of health]. / Voenno-professional'naia rabotosposobnost' kak kriterii zdorov'ia.

The indices of physical, sensor and task performance were used to characterize and estimate the functional state of military specialists and their functional reserves. Application of these criteria gives the possibility for physician-prophylaxist to obtain a truly information about the health status in the military unit making a selective control in it.