Search

The success of two monkeys in performing an eye-head-hand coordination task was investigated during the Bion 11 flight. In comparison to the ground controls, it took the flight monkeys more time to reach the light stimuli located at 40 degrees to the left or right from the center of the panel in front of them. During flight days (FD) 5-6, the precision of hand movements deteriorated, and during FD 7-14, it improved, although the performance time increased.

Cross-interval and cross-correlation analysis of neuron activity was used to study cell interactions in the cerebellar vermis of conscious rabbits. The cross-correlation method, based on post-synaptic potentials (PSP) from one member of a pair of neurons, supplements the cross-interval analysis used for evaluating the interactions of neurons in terms of action potentials. A total of 16 neuron pairs were analyzed, in which the activity of one neuron was recorded intracellularly and that of the other extra- or intracellularly. Interactions were observed in 10 pairs. Most pairs showed inhibitory interactions. Pairs with inhibitory interactions included those in which the activity of one or both neurons contained complex spikes. Also of interest was the analysis of connections in which influences were excitatory in one direction and inhibitory in the other. In these cases, neuron discharges were invariably simple spikes. Variability and plasticity in the output signals of Purkinje cells were greater than the variability and plasticity of the common inputs to Purkinje cells.

The methods of cross-interval and crosscorrelation analysis were used to study interneuronal connections in cerebellar vermis in awake rabbit. Crosscorrelation, or spike-triggering method, complemented the analysis of cross-intervals which estimated the neuronal interaction comparing spike sequences as point processes. Among 16 neuronal pairs recorded intra- or extracellularly 10 pairs were considered as interconnected. Inhibitory interconnections dominated. The inhibitory neuronal interconnections were revealed in pairs with complex spikes. Neurons which constituted pairs with reciprocal excitatory-inhibitory interaction fired only simple spikes. The variability and plasticity of common inputs to Purkinje cells were seemingly lower than those of direct connections which probably transmitted the output signals of Purkinje cells.

The postsynaptic changes in the focal potentials of the sensorimotor cortex of the awake rabbit was investigated in this study following tetanization of the corpus callosum and the white matter. Stimulation of these structures was carried out during testing. A prolonged (hour-long) increase in the amplitude of the responses was observed in some of the experiments following tetanization, as compared with the control prior tetanization. Just as long a decrease in the amplitude of the responses tested developed in a number of experiments in the posttetanic period. It was concluded that prolonged plastic changes can occur in different directions in the sensorimotor cortex of the awake rabbit.

Study of posttetanic changes in the sensorimotor cortex of the alert rabbit in response to stimulation of callosal fibres of the white matter have shown that in comparison to the control level either a prolonged increase (potentiation) of the tested evoked potentials to the stimulation of the same structures takes place, or the amplitude of the tested evoked potentials decreases (depression). Both processes can take place simultaneously in different layers of the cortex.

Two millimeter range ESR-spectroscopy was used to measure the values of magnetic resonance parameters of egg lysozyme samples modified with nitroxyl label 4-(iodine-acetamide)-2,2,6,6-tetramethylpiperidine-1-oxyl by hist-15 residue. It has been shown that in a lyophilic sample the spin label forms a hydrogen bond with the protein group and when the sample is moistened--with water molecules. Temperature changes of the pattern of ESR line are analysed. It is concluded that in the moistened samples within 230-320 K the nitroxyl fragment of the label gets engaged in anisotropic movement with preferable rotation around Z-axis of N-O. fragment with anisotropy coefficient 5 and mean correlation time tau congruent to 5 X 10(-7) divided by 5 X 10(-8) c.

The activity of neurons in the rostral part of the fastigial nucleus was recorded during fictious scratch reflex (FSR) in immobilized cats. During FSR the discharge frequency of many fastigial neurons was rhythmically modulated in relation to the scratch cycle: most of them fired in bursts at the end of the flexor phase or at the extensor phase of the cycle. The firing pattern of fastigial neurons was similar during both ipsilateral and contralateral FSR. Therefore the fastigial nuclei exert bilateral influences on the brain stem structures during one-sided motor activity.

Electrical parameters of the sensomotor cortex neurons were studied in unanesthetized rabbits. The values of mean interspike membrane potential, spike threshold, spike "failures" and duration were computed in 800-spike epochs. Scatter diagrams and the data obtained for the parameters provided additional usable information.

In adult cats and 1--16--day kittens, repeated stimuli of less than 1/sec and supramaximal strength applied to afferent fibers of nervus ischiadicus evoked the multicomponent responses recorded from efferent fibers of n. hypogastricus. Latencies of responses components decreased during postnatal development. In all the animals basic three responses remained unchanged after Th10-12 chordotomy. Stimulation of kittens afferent somatic fibers with frequency of 10/sec and of variable strength enhanced the sympathetic nerve activity and in rare occasions suppressed it. In adult animals the sign of sympathetic nerve response depended on the level of spontaneous sympathetic activity and on the stimulus strength. This relation remained unchanged after the chordotomy. In chordotomised kittens repeated stimuli applied to somatic nerve produced the sympathetic nerve activation alone.

A method of comparative analysis of ESR spectra has been proposed. It allows to distinguish between two models, slow reorientation of spin labels, and rapid rotation of the cone. Comparison of experimental data for a number of biological objects the theoretical predictions has shown that the rotation of nitroxyl fragment of spin labels can be described by the model of slow anisotropic rotation with correlation time 10(-6) less than or equal to tau less than or equal to 10(-8) s in conditions where the rotation of macromolecules is "frozen".