[Bioelectrical activity of the brain in rabbit fetuses in relation to the duration of umbilical cord occlusion]. / Bioélektricheskaia aktivnost' mozga plodov krolika v zavisimosti ot dlitel'nosti perezhatiia pupoviny.

Studies have been made on the EEG reactions in 20-, 25- and 28-day rabbit foetuses after complete occlusion of the umbilical cord. It was shown that in 20-day foetuses, EEG after the occlusion of the umbilical cord is presented mainly by low frequency waves. Significant decrease in the EEG amplitude took place to the 120th min, isoelectric stage was observed at the 150th min. In the frequency spectrum, the low frequency activity increased from 22.44 to 30.50%. As revealed by ECG control, the survival time after the occlusion of the umbilical cord is equal to 150 min. In 25-day foetuses, the decrease in the EEG amplitude was observed at the 150th min, isoelectric stage--to the 120th min. All the frequencies in the EEG spectrum were decreased. The survival time of foetuses was equal to 120 min. In 28-day foetuses, after the occlusion of the umbilical cord, a gradual decrease in the amplitude of EEG was observed from the 1st to the 60th min. Isoelectric stage occurred at the 105th min. Foetuses survived for 105 min. It is concluded that after the occlusion of the umbilical cord, re-arrangement in the EEG pattern takes place which includes two critical periods: the first one--immediately after the occlusion--is associated presumably with the reflex reaction of the organism of the foetus, whereas the second period includes the last minutes of survival, when a complete failure in the system of compensatory autoregulation is observed.

Electrophysiological investigation of hypothalamo-neocortical connections in Macaca mulatta.

Functional relations between phylogenetically different parts of the hypothalamus and the neocortex were studied by the method of recording evoked potentials (EP) and evoked single unit responses in acute experiments on monkeys (Macaca mulatta). The focus of maximal activity of EP and of single unit responses was found to be in the frontal association cortex, where evoked responses with the shortest latencies were recorded. During stimulation of the posterior hypothalamus, mainly unit responses of excitatory character were recorded in the neocortex, whereas during stimulation of the lateral hypothalamus mainly unit responses of inhibitory character were recorded.

[Functional interactions between the rabbit hypothalamus and neocortex]. / Funktsional'nye vzaimootnosheniia gipotalamusa i neokorteksa u krolika.

In acute experiments on rabbits under chloralose-nembutal anaesthesia, studies have been made on the distribution and the pattern of the evoked potentials (EP) in neocortical structures of the brain cortex during electrical stimulation of different hypothalamic nuclei. It was found that during stimulation of the supramammilar area of the hypothalamus, the focus of maximum activity of cortical responses of the negative-positive configuration is localised in the median parts of precentral agranular region. During stimulation of the posterior hypothalamic area, the EP were of the positive-negative-positive type. Registration of the EP in different cortical layers during stimulation of the posterior hypothlamic nuclei showed that from 100 to 100 micrograms the amplitude of EP components decreases, whereas at the level of 600 mu the inversion of the EP takes place. At the depth of 1.800 mu the EP elicited by stimulation of the posterior hypothalamus had a form of a positive oscillation with a long latent period. It is concluded that the posterior hypothalamic nuclei have a vast representation in rabbit neocortex, this representation being realized by both polysynaptic and olygosynaptic systems of connections.

[Electrophysiologic study of hypothalamo-neocortical connections in Macaca mulatta monkeys]. / Elektrofiziologicheskoe issledovanie gipotalamo-neokortikal'nykh sviazei u obez'iany Macaca mulatta.

In acute experiments on monkeys studies have been made on the character and functional properties of the EP as well as of extracellular neuronal reactions in the new cortex zones during stimulation of phylogenetically different parts of the hypothalamus. It was shown that most short-latency, low-threshold EP and neuronal responses in the new cortex of the monkeys are recorded during stimulation of the posterior and lateral hypothalamus. It was also demonstrated that the focus of maximum activity of short-latency evoked reactions is localized in the frontal associative cortex. Differences in the effects of the posterior and lateral hypothalamus on the new cortex in monkeys are discussed.

[Electrophysiological study of the functional connections of the hypothalamus with the forebrain in the tortoise Emys orbicularis]. / Elektrofiziologicheskoe issledovanie funktsional'nykh sviazei gipotalamusa s perednim mozgom u cherepakhi Emys orbicularis.

During stimulation of the posterior hypothalamus, the evoked potentials with short latent periods, high amplitude and poor exhaustion by rhythmic stimulation were recorded in the hippocampal cortex. In the piriform cortex, the evoked potentials exhibited longer latent periods and complex configuration. Less readily the evoked potentials appeared in the neocortex, their latency being very large. During stimulation of the anterior hypothalamus, maximum activity was also localized in the hippocampal cortex. The data obtained indicate close connection between hypothalamic structures and the hippocampal cortex. The latter is presumably the main projectional area for the ascending afferentation from the hypothalamus.