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Biomedical subjects

M G Tsagareli

Publications and source records attributed to M G Tsagareli.

10 recordsLinked to original sources
PubMed1995

The interhemispheric functional organization on human visuo-spatial perception.

To investigate the number of correct responses (NCR), the reaction time (RT) and the event-related potentials (ERPs), the visuo-spatial perception of geometric figures in conditions of backward masking was studied in healthy subjects and patients with chronic alcoholism. The performance of a visuo-spatial task of mentally constructing geometric figures was found to be achieved better if a figure-standard could be formed from the presented fragments. The NCR was significantly lower and the RT longer in patients than in healthy subjects. During the solution of this task in controls the RT was shorter if the stimuli were presented in the left visual field. No interhemispheric differences were observed in alcoholics. The late components of ERPs N200 and P300 occurred with a longer latency and lesser amplitudes in patients than in normal controls. Smaller ERP amplitudes were observed in the right hemisphere. The findings support the view that in chronic alcoholism the hemispheric interaction is disturbed due to predominant deficiency of the visuo-spatial function in the right hemisphere.

Adult↗
PubMedDate not supplied

Lateralization of visual-spatial perception in man in conditions of verbal reinforcement.

Studies were carried out on the effects of positive and negative verbal reinforcement on the mental ability of normal subjects and patients with chronic alcoholism to construct standard geometrical shapes from two fragments presented tachystoscopically. Negative verbal reinforcement in healthy subjects produced reductions in the latent period and increases in the amplitude of evoked N200-P300 potentials, particularly in the right parietal lobe and the vertex. These changes were not observed in patients, and patients lesser ability to carry out visual-spatial tasks could be explained by the general reduction in evoked brain potentials and the disappearance of interhemisphere functional asymmetry, which plays an important role in visual-perceptive activity in man.

Adult↗
PubMedDate not supplied

[Lateralization of visuo-spatial function during masking in healthy subjects and in patients with chronic alcoholism].

In healthy subjects and patients with chronic alcoholism, the ability to construct in mind geometric figures in conditions of masking was studied by means of recording the number of correct decisions, the reaction time and evoked cortical electrical activity. It has been found that solution of visual-spatial task of mentally constructing geometric figures is accomplished better if a figure-standard can be formed from the presented fragments. During solution of the visual-spatial task in norm the reaction time is shorter if the information comes "directly" to the right hemisphere. Such interhemispheric differences are not observed at chronic alcoholic intoxication. In patients with chronic alcoholism the late components of EPs N200 and P300 developed with a longer latency and lesser amplitude than in healthy subjects. The greatest depression of cortical activity is observed in the right hemisphere.

Adult↗
PubMedDate not supplied

[Plastic changes in responses of chemo- and electro-excitable membranes of a cortical neurons following orthodromal tetanization].

Orthodromic tetanization produces in the turtle visual cortex two types of reversible plastic changes of electrical responses: facilitation and depression. Posttetanic facilitation is attended with reversible enhancement of evoked postsynaptic potentials and APs; the excitability of the electroexcitable membrane increases: the critical level of depolarization of the evoked spike shifts in the negative direction and its threshold potential decreases. Posttetanic depression is accompanied by a reversible decrease of the amplitude of evoked postsynaptic and spike potentials; the excitability of the electroexcitable membrane decreases: the critical level of depolarization of the evoked spike shifts in the positive direction, and its threshold potential increases. Reversible changes of excitability of the spike generating membrane following tetanization testify to the existence of an active mechanism of spike discharge change.

Animals↗
PubMedDate not supplied

[Post-tetanic changes in the excitation threshold of the excitable membrane of a cortical neuron by a depolarizing current].

Posttetanic plasticity of cortical neurone is attended with reversible changes in the threshold of stimulation of the electrically excitable membrane with depolarizing current, and in its excitability. In the period of posttetanic facilitation, the stimulation threshold is lowered while the membrane excitability is enhanced. In the period of posttetanic depression, the stimulation threshold is higher, the membrane excitability is reduced. Definite directions of changes in the threshold of stimulation of the electrically excitable membrane with depolarizing current and, correspondingly, in its excitability, peculiar to each kind of posttetanic plasticity, testify to active contribution of the membrane to the organization of plastic rearrangements of the neurone's spike response.

Action Potentials↗
PubMedDate not supplied

[The lateralization of human visual-spatial perception during verbal reinforcement].

Influence of positive (word "good") and negative (word "mistake") verbal reinforcement on the ability of mental construction of six geometric figures from two fragments administered tachistoscopically under backward masking conditions was studied in healthy persons and patients with chronic alcoholism. In healthy persons negative verbal reinforcement induced a reduction in the latency of N200 and growth of the amplitude of N200-P300 components of evoked potentials mainly in the right parietal area and vertex. There were no such changes in patients. Worse performance of the visuo-spatial task by the patients may be explained by the general suppression of the brain evoked potentials and disappearance of interhemispheric asymmetry which is characteristic for healthy persons and play an important role in visuo-spatial perception.

Adult↗
PubMedDate not supplied

[The hemispheric functional specialization of visual perception].

In this review the modern concepts on psychophysical mechanisms of hemispheric functional specialization of human visual perception are considered. The problems are discussed on three basic historical aspects: interhemispheric relations in patients with localized cerebral lesions, interhemispheric differences in the "Bisected Brain", and the functional asymmetry in the intact brain. The neuropsychological data on recognition of geometric figures, faces and objects, and also electrophysiological results on the event-related brain potentials are deliberated. Special attention is given to the own data of authors dedicated to importance role of the right hemisphere in the brain interhemispheric functional asymmetry in control subjects and alcoholics. Several problems on learning and influence of emotions on visuospatial recognition are discussed. The dichotomous approach to brain functional asymmetry are not shared, the hypothesis on intersupplementary cooperation in hemispheric specialization and interaction of the brain hemispheres are supported.

Alcoholism↗