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Biomedical subjects

S A Lytaev

Publications and source records attributed to S A Lytaev.

At least 19 recordsLinked to original sources
PubMed1999

[Monitoring of the auditory stem evoked potentials in removal of tumors of the posterior cranial fossa].

The material of intraoperative monitoring of the acoustic stem evoked potentials (ASEP) in 9 patients with tumors of the stem and in 28 patients with the parastem localization was analyzed. It was shown that changes in the amplitude of ASEP rather than latency were the decisive factor in the assessment of the functional state of the brain stem. It was found that even the pronounced changes of the bioelectrical activity recorded during the excision of the tumor could be reversible after a change of the strategy of the operative intervention and/or after performing the necessary therapeutic measures. An important test of favorable prognosis of the postoperative course is considered to be the normalization of brain activity, ASEP included, at the final stages of the operation.

Adolescent↗
PubMed1996

[Modern diagnostic methods in multiple sclerosis].

161 patients with multiple sclerosis were observed according to C. M. Poser's scale. The diagnosis was definite in 73.9% of cases, probable--in 14.9% and doubtful in 11.2% of patients. The diagnostic significance of magnetic resonance tomography (MRT) was estimated as well as of visual evoked potentials (VEPs), mid-latency auditory evoked potentials (MAEPs), viscocontrastoperimetry and pallesthesiometry (vibratory sensation). MRT revealed alterations in 80.3% of 71 cases (97.5% at definite diagnosis). The results of investigation of evoked potentials differed from normal values: VEPs in 100%, MAEPs in 72.6% of 26 patients observed. Visocontrastoperimetry revealed disorders in 75,2% of 113 cases, pallesthesiometry in toes--in 100%, in fingers--in 68.9% of 116 patients observed.

Adult↗
PubMed1993

[The topographic mapping of evoked bioelectrical activity and other methods for the functional neural visualization of the brain].

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.

Adolescent↗
PubMedDate not supplied

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.

Acoustic Stimulation↗
PubMedDate not supplied

[Reorganization of the pattern of the brain somatosensory evoked potentials after spinal cord injury].

Recordings of somatosensory evoked potentials (SEPs) and SEP brain maps of 23 patients with vertebral injury were analyzed. All patients were operated at the Clinic of Military Traumatology and Orthopedics, Military Medical Academy. SEPs (19 sites) were recorded in real time and mapped with "Brain surveyor" neuromapper. Brain lesions were localized before surgery by of MR imaging and CT standard techniques. The results demonstrate that electrical stimulation of peripheral nerves produces a substantially variable SEP pattern. It was shown that SEP formation in more than 60% of recordings suggests a favorable prognosis for rehabilitation, whereas if more than 50% of recording sites are unresponsive, the rehabilitation prognosis is unfavorable. The amplitude of early components (below 60 ms) increases, and that of the late waves reduces.

Adult↗
PubMedDate not supplied

[The thalamic integration of afferent flows in man during image recognition].

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.

Acoustic Stimulation↗
PubMedDate not supplied

[The characteristics of perceptive learning and memory in psychopathological states].

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.

Acoustic Stimulation↗
PubMedDate not supplied

[Methods for analyzing brain evoked potentials clinically and in psychophysiology].

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.

Brain Mapping↗
PubMedDate not supplied

[The topography of the afferent and efferent flows in the mechanisms of auditory selective attention].

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.

Acoustic Stimulation↗
PubMedDate not supplied

[The significance of emotional processes in man in the mechanisms of analyzing the effect of varying contrast stimulation].

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.

Adult↗
PubMedDate not supplied

[The reflection of the augmenting-reducing phenomenon in the characteristics of the spatial-temporal EEG indices].

Phenomenon of augmenting-reducing was studied based on Livanov's concept on the spatial synchronization of biopotentials, multi-channel EEG recordings being used. Augmenting-reducing phenomenon is a certain type of response to any coming information. When single light flashes of increasing intensity were applied to 21 human subjects the phenomenon under study displayed wide spatial distribution. In experiments with rhythmical light stimulation the leading role of the spatially limited bioelectrical processes was shown. About 50% of the subjects retained interhemispheric asymmetry in the course of an experiment.

Brain Mapping↗