Correlation between the sizes of Mauthner neurons and the preference of goldfish to turn to the right or left.

Three-dimensional computer reconstruction working from serial histological sections was used to study the morphology of the right and left Mauthner neurons (MN) in goldfish fry showing marked preferences to turn stably to the right or left in a narrow water channel or showing no asymmetry in their choice of side during turns. Visually, fish with left-sided motor asymmetry had larger MN on the right side, while fish with right-sided motor asymmetry had larger MN on the left side. Fish with symmetrical turns to the right and left showed no differences in MN size. Quantitative assessment of the MN of fish with preferences for turns to one side or the other revealed significant differences in the sizes of the somatic part, the axon hillock, and the axons of neurons located on the contralateral side of the medulla oblongata. Analysis of the statistical relationships between the functional (motor) asymmetry of fish and the morphological asymmetry of the somatic parts of MN in the same fish revealed a stable correlation (0.69) between these measures. Given that MN initiate unilateral turns of the body in free movement, the data obtained here lead to the conclusion that the larger neuron is more frequently activated in natural conditions as compared with the smaller, contralateral, neuron.

[Correlation of the sizes of Mauthner neurons with the preference in the goldfish to turn rightwards or leftwards].

Using the three-dimensional computer reconstruction from serial histological sections, the morphology of right and left Mauthner cells (MC) was examined in the goldfish fry which demonstrated clearly pronounced preference to turn to the right or to the left in a narrow water channel or which did not show any asymmetry in choosing the side of turning. Visually, the goldfish with left-sided motor asymmetry seemed to possess larger right MC, while in the goldfish with right-sided motor asymmetry left MC were larger. In fish with symmetric proportion of right or left turnings, the sizes of MC did not differ. Quantitative evaluation of MC in fish showing the preference of turning side has revealed significant differences in the sizes of cell bodies, axon hillock and axons of MC, located contralaterally in medulla oblongata. Analysis of a statistic relations between functional (motor) and morphological asymmetry of MC cell body in the same fish indicated the existence of a stable correlation (0,69) between them. Taking into consideration that MC initiate unilateral body turn during free swimming of fish, it may be concluded that the larger size of neuron predetermines its more frequent natural activation in comparison with the contrlateral neuron, that has smaller size.

Features of the coordinated activity functionally identified neurons in the hypothalamus in different motivational-emotional states.

Coordinated activity of hypothalamic neurons associated with motivational and reinforcing systems were studied in functional states arising from hunger, satiation following food deprivation, "victim" cries, and electrical stimulation of the emotionally positive (lateral hypothalamus, lateral preoptic region) and negative (dorsomedial tegmentum) reinforcing structures of the hypothalamus. Activity characteristics were reflected in the magnitude, sign, and dynamics of correlations, and depended on the ratio of motivational and emotional components of behavior. The reciprocal nature of the statistical significance of the activity of these neurons in conditions in which motivation and emotion dominated indicates that the differentiated motivational and emotional hypothalamic influences in cortical processes during learning are mediated via the coordinated activity of neurons in the motivational and reinforcing systems of the hypothalamus.

Phase relationships between the rhythmic activity of cortical structures of the rabbit at different midbrain reticular formation stimulation frequencies.

An investigation of the phase shifts between rhythmic constituents of the electrical activity of the hippocampus, somatosensory, motor, and visual areas of the neocortex of the rabbit during an increase in the frequency of stimulation of the reticular formation from 60 to 1000 imp/sec revealed the fluctuating character of the decrease in the phase shift in the theta range in pairings involving the visual area and of its increase in the remaining pairings. In the delta range, at the same time, an increase was observed in the phase angle in pairings between the hippocampus, somatosensory, and motor areas at a stimulation frequency above 200 imp/sec, while in the alpha range the changes in the phase shift were variously directed in character.

[The characteristics of the coordinated activity of functionally identified hypothalamic neurons under different motivational-emotional states]. / Osobennosti soglasovannoi deiatel'nosti funktsional'no identifitsirovannykh neironov gipotalamusa pri raznykh motivatsionno-émotsional'nykh sostoianiiakh.

Simultaneous impulse activity of pairs of neurons in hypothalamus was analysed in different natural functional states of rats (hunger, satiation after food deprivation, cry of a victim) and those induced by electrical stimulation of the emotionally positive (lateral hypothalamus, lateral preoptic area) and negative (dorso-medial tegmentum) reinforcing hypothalamic structures. Two classes of neurons were separated according to the pattern of their activity determined by the motivational state or reinforcement. Characteristic features were revealed in the patterns of conjugate activity of the functionally identified neurons. They were determined by the dominance of motivational or emotional component in the behaviour of an animal and manifested in a specificity of temporal delays in impulsation of one of the neurons in respect to the other one, in magnitude and number of positive and negative correlations. The results suggest the different ways of realization of the motivational and reinforcing hypothalamic influences mediated by the neurons of the motivational and reinforcing systems, on the cortical processes at different stages of learning which also differ in the balance between the motivational and emotional components of the animal behaviour.

[An ultrastructural study of the hippocampal neurons in mice subjected to heat exposure]. / Izuchenie ul'trastruktury neironov gippokampa myshei, podvergnutykh teplovomu vozdeistviiu.

The ultrastructure of hippocampal neurons in mice subjected to heat treatment for 40 min at 42 degrees C was studied. Such a treatment has been shown to result in significant changes in the structure of pyramidal neurons. An increased chromatin condensation in the nuclei was found in addition to deep invagination of their envelopes and reduction or fragmentation of the reticulum cisterns. These changes were accompanied by mitochondrial swelling and increased number of clathrine vesicles around the Golgi complex. The heat exposure followed by feeding on vitamins and beta-carotin appeared to diminish chromatin condensation and kept the cisterns invariable.

[The phasic relations between the rhythmic activities of the rabbit cortical structures at different frequencies of stimulation of the midbrain reticular formation]. / Fazovye otnosheniia mezhdu ritmicheskoi aktivnost'iu korkovykh struktur krolika pri razlichnykh chastotakh stimuliatsii retikuliarnoi formatsii srednego mozga.

Phase shifts between the rhythmical activity of the hippocampus (CA1), somatosensory, motor and visual areas of the neocortex in the delta-, theta- and alpha-bands were studied during electrostimulation of the mesencephalic reticular formation with different frequencies. It was found that increasing stimulation frequency resulted in nonlinear decrease of the phase shifts in the theta-band between recordings which included the visual cortical area, and increase of the phase shifts between the theta-rhythm, recorded in the hippocampus, somatosensory and motor cortical areas. In the delta-band increase of the phase shifts was observed only in the pairs of recordings from the last-mentioned group of structures at stimulation frequencies more than 200 1/sec. Phase shifts in the alpha-rhythm between the cortical recordings varied at different stimulation frequencies. Reliable changes of the alpha-rhythm phase shifts were observed during stimulation with the frequency 60-200 1/sec between recordings from the hippocampus, motor and somatosensory areas, and at 500-700 1/sec--in the pairs of recordings which included the visual cortical area.

[Spectral characteristics of the EEG of the visual and motor cortices in the rabbit during stimulation of the reticular formation of the brain]. / Spektral'nye kharakteristiki EEG zritel'noi i motornoi kory krolika pri razdrazhenii retikuliarnoi formatsii mozga.

Study of amplitude-frequency characteristics of dominating spectral maxima in the delta, theta and alpha-ranges of the rabbit visual and motor neocortical areas has shown that an increase of the midbrain reticular formation stimulation frequency from 60 to 1000 imp/s leads to an increase in both area of dominating rhythms frequencies in the theta and alpha-ranges, and to a decrease of the alpha-rhythm amplitude. The theta-rhythm amplitude in the visual area declines while in the motor area a slight increase is observed and then a decrease. Characteristics of the dominating frequency component in the delta-range are determined by three types of oscillations with different types of dependence on frequency of reticular formation stimulation. The most significant differences between areas are manifest in the spectrum amplitude characteristics. Qualitatively similar changes are also seen in correlation of power of spectral ranges in both areas but quantitatively they are more expressed in the motor area.

[Dependence of the spectrum of electrical activity of the neocortex and hippocampus in rabbits on the intensity of the stimulation of the midbrain reticular formation]. / Zavisimost' spektra élektricheskoi aktivnosti neokorteksa i gippokampa u krolikov ot intensivnosti stimuliatsii retikuliarnoi formatsii srednego mozga.

Study of dominating spectral maxima in delta-, theta- and alpha-ranges of the electrical activity of rabbits' neocortex and hippocampus showed that an increase of the frequency of the mesencephalic reticular formation stimulation from 60 to 200 imp/s led in both structures to an enhancement of the theta-rhythm (up to 130% in the neocortex and 147% in the hippocampus) and suppression of delta- and alpha-activity (correspondingly up to 67 and 34% in the neocortex and 37 and 48% in the hippocampus) with subsequent weakening of this effect at frequency increase up to 1000 imp/s. In the hippocampus, the reticular stimulation was more effective with respect to the theta- and delta-rhythms, and in the neocortex--with respect to the alpha-rhythm. In both structures the theta-rhythm amplitude changed less than the amplitude of the delta- and alpha-activities. Dependence of the amplitude of dominating rhythms on intensity of reticular formation stimulation differed from the analogous frequency dependence of the same rhythms.

[Electrophysiological indices of the degree of functional integration of a cortical transplant with the brain of the recipient]. / Elektrofiziologicheskie pokazateli stepeni funktsional'noi integratsii kortikal'nogo transplantata s mozgom retsipienta.

Pieces of the embryonal rat neocortex were grafted into the cavity at the place of the barrel-field of adult rats. Neuronal discharges and slow activity were recorded in 11 grafts 3-8 months after the grafting. Neurons of nine grafts responded to vibrissae deflection, their background activity consisted of randomly distributed discharges as in the normal cortex. The similar slow activity was observed in the responding grafts and in the host's intact contralateral barrel-field. Neurons of two grafts did not respond to vibrissae deflection. Hypersynchronous discharges prevailed in their background activity as well as slow delta-waves and epileptiform sharp spikes and waves. Complexes predominated in slow activity of these grafts. Histology revealed a close contact between responding grafts and host brain tissue. Nonresponding grafts were separated from the host brain by a thick glial scar which apparently prevented the axonal exchange between them.