Electrophysiologic correlates of habituation and conditioned reflex elaboration

The average correlation coefficient between the EEG of different parts of the cortex gradually decreases as the rabbit is habituated to the experimental surroundings. Elaboration of an electo-defensive conditioned reflex leads to its enhancement which is replaced by a phase of temporary decrease, to be followed again by an enhancement of EEG correlation. The pronouncedness of theta-frequencies in the spectral and coherent functions behaves in a similar way. Successive changes of delta-activity level reveal no regularity.     

Amplitude-temporal characteristics of evoked responses of the visual analyzer to stimuli of growing intensity

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.     

Rhythmical processes in the cerebral cortex bioelectrical activity in arousal reaction: qualitative nonlinear analysis involving refractoriness

An integral equation that takes into account the absolute and relative refractory periods of cortical cells was added to the earlier obtained integral equations describing the cooperation of excitatory and inhibitory neurons of the cerebral cortex, and its substantiation was suggested. The steady states and the stable region of oscillations of the mean membrane potential of excitatory neurons were investigated depending on the mean afferent influx value on the assumption of the normal threshold distribution of cells. The existence of a parameter multitude in the region of stability was shown when a suppression of the delta-rhythm and an enhancement of the theta-rhythm up to its dominance take place increasing nonspecific afferent influx, which shows up a white noise, and decrease of the theta-rhythm during further increase in nonspecific activation. Simultaneously the frequencies of the major cerebral rhythms increase. The conformity of the theoretically calculated dependences of changes of the spectrum upon increasing nonspecific afferent influx to the experimental data obtained during the electrical stimulation of the rabbit midbrain reticular formation was demonstrated.     

Rhythmic bioelectrical activity of the cerebral cortex analyzed with allowance for the nonlinear voltage dependence of excitatory postsynaptic potentials induced by neocortical neurons

A nonlinear voltage dependence between the membrane and excitatory postsynaptic potentials coming via corticocortical connections was derived based on literature data. The existence of a region of stability of oscillations with increasing mean value of nonspecific afferent input was shown. As the afferent input strongly increases, a high-frequency component of oscillations (40-60 Hz), appeas which may result in the instability of oscillations and initiation of abnormal brain activity.     

Energy distributions of superthermal ions in regime with sawtooth oscillations during neutral beam injection at the Globus-M tokamak

Specific features of the energy distributions of fast ions during neutral beam injection at the Globus-М tokamak are considered. Different loss mechanisms that can lead to the formation of a specific shape of the energy spectrum of superthermal ions are analyzed. The effect of sawtooth oscillations on the loss of fast ions is discussed.     

Structural changes in the brain according to computed tomographic data in patients undergoing combination therapy for hemispheric gliomas]

Basing on CT data, the authors analyze the qualitative changes in the brain of patients with a history of multiple-modality treatment for immature neuroectodermal tumors. Plani- and volumetric parameters of the total brain, the involved and the contralateral hemispheres are compared with the same parameters in the reference group. The pattern and degree of structural changes were found related to the site of the tumor and surgery. The brain matter in both hemispheres was lost mostly in the interstitial and end portions predominantly on the side of the tumor and surgery. Changes of the brain were individual in the patients.     

Investigation of the plasma radiation power in the Globus-M tokamak by means of SPD silicon photodiodes

Radiation losses from the plasma of the Globus-M tokamak are studied by means of SPD silicon photodiodes developed at the Ioffe Institute, Russian Academy of Sciences. The results from measurements of radiation losses in regimes with ohmic and neutral beam injection heating of plasmas with different isotope compositions are presented. The dependence of the radiation loss power on the plasma current and plasma–wall distance is investigated. The radiation power in different spectral ranges is analyzed by means of an SPD spectrometric module. Results of measurements of radiation losses before and after tokamak vessel boronization are presented. The time evolution of the sensitivity of the SPD photodiode during its two-year exploitation in Globus-M is analyzed.     

Prenatal DNA-diagnosis of Duchenne muscular dystrophy]

Two prenatal diagnoses were carried out by the technique of intragenic polymorphous marker detecting heterozygosity in pregnant women in the families with cases of Duchenne muscular dystrophy. In both cases the DNA fragment from pERT87-15 region was amplified. This fragment includes a polymorphous site in BamHI region of recognition. DNA analyses of the families members have been made and the genetical risk has been calculated by the Bayes method. The prognoses for both fetuses are good.