Locus ceruleus and neuronal activity of the reticular nucleus of the thalamus.

Reactions of neurons of the reticular nucleus of the thalamus and lateral geniculate body to stimulation of the locus ceruleus were studied on their unanesthetized, immobilized cats. It was found that preliminary brief rhythmic stimulation of the locus ceruleus causes inhibition of the activity of the majority of neurons of the reticular nucleus and facilitation of relay neurons of the lateral geniculate body. Such reactions are clearly exhibited during simultaneous recording (by means of two microelectrodes) of the neuronal activity of these brain structures.

[Relation between sleep and processes of retention and mental activity]. / O sviazi sna s protsessami zapominaniia i umstvennoi aktivnost'iu.

The structure of nocturnal sleep was studied in two groups of subjects: the group I subjects had been given 60 unfamiliar English words to learn, whereas Group II subjects had been playing games of chess. The paradoxical sleep (PS) latency in the 1 st cycle, the type of falling into the PS, and intensity of rapid eye movements were recorded. No reliable difference was found in the sleep structure of both test groups. No correlation either was observed between the sleep characteristics and the quality of memorizing the verbal material.

[The locus coeruleus and neuronal activity of the thalamic reticular nucleus]. / Sinee piatno i neironnaia aktivnost' retikuliarnogo iadra talamusa.

The influence of LC stimulation on the unit activity (spontaneous and evoked by light flashes) of the thalamic reticular nucleus and the LGB was studied in adult cats. The LC stimulation was shown to result in the inhibition of the reticular units and facilitation of relay neurons of the LGB.

[Neuronal activity of cat thalamus reticular and relay nuclei]. / Neironnaia aktivnost' retikuliarnogo i peredatochnykh iader talamusa koshki.

The interaction between the unit activity of the thalamic reticular and relay nuclei was investigated on cats immobilized with tubarine. It was shown that unit activity of the relay nuclei can be significantly modulated by stimulation of the n. reticul. By simultaneous recording (with two microelectrodes) of the activity of thalamic reticular neurons the relay unit activity can be suppressed; during peripheral and cortical stimulations the alternation of excitation-inhibition of the thalamic reticular and relay units can be observed; excitation of thalamic reticular units can be associated with excitation of the relay nuclei units. Such types of interaction may also exist during simultaneous recording (by two microelectrodes) of the activity of the relay units and putative interneurons. Sometimes IPSPs with short latency (1 ms) were evoked in the thalamic relay nuclei during thalamic reticular stimulation. The existence of direct monosynaptic inhibition of the relay unit activity by the thalamic reticular units as well as inhibition by the activation of the putative interneurons of the specific thalamic nuclei is suggested.

[Interaction between spindles evoked by electric stimulation of different regions of the cerebral cortex]. / K vzaimodistviiu vereten, vyzvannykh élektricheskim razdrazheniem raznykh oblastei kory bol'shikh polusharii golovnogo mozga

In unanesthetized immobilized cats, under repeated administration of small doses of nembutal (2-3 mg/kg), connections between the projection and the parietal associatition cortical areas was studied as well as the interaction between spindles elicited by stimulation of these areas. Stimulation of the primary sensory areas (auditory or somatosensory) was shown to be able to elicit spindles not only in the stimulated area but in the association cortex too. This latter spindle, being kind of induced from the sensory areas, interacts with the spindles elicited by the direct electrical stimulation on the association cortex.

Facts and reflections on thalamocortical reverberation of impulses.

Experiments on cats, either unanesthetized or anesthetized with various doses of pentobarbital, showed that the cortical rhythmic after-discharge ("slow after-activity"), which has been regarded as a manifestation of reverberation of impulses in thalamocortical circuits [17], consists of a burst of spontaneous "spindles" evoked by stimulation. This conclusion is supported by the following facts: Spontaneous "spindles" and the rhythmic after-discharge respond absolutely identically (disappear) to activation of the EEG and deepening of pentobarbital anesthesia. The absence of thalamocortical reverberation is also indicated by the preservation of a rhythmic after-discharge (to clicks), synchronous with the cortex, in the thalamic relay nucleus (the medial geniculate body) after cooling or after removal of its projection zone.

[Thalamocortical relationships during spontaneous and evoked rhythmic activity of the brain]. / Talamokortikal'nye otnosheniia pri spontannoi i vyzvannoi ritmicheskoi aktivnosti golovnogo mozga

A study was made in lightly nembutalized and unanaesthetized immunobilized cats of the interrelations between rhythmic afterdischarge evoked in the auditory cortex by a click, and a spontaneous spindle burst under different states of intact animals. The experiments showed: 1) Rhythmic afterdischarge represents a stimulus induced spindle burst, 2) local spindle burst (spontaneous or evoked by peripheral and central stimulations) in the auditory cortex does not change considerably either by stimulation or by lesion of thalamic nonspecific, as well as other specific structures; 3) An afterdischarge in the medial geniculate body (evoked by a click) remains unchanged after cooling or extirpation of the whole auditory cortex. All this suggests a generation of both spontaneous and evoked local rhythmic activity of the auditory thalamo-cortical system, independent of other such systems.

[Findings and reflections on the reverberation of thalamocortical impulses]. / Nekotorye dannye i soobrazheniia o talamokortikal'noi reverberatsii impul'sov

Chang's experiments showing the rhythmic afterdischarge in slightly nembutalized cats which he considered as a manifestation of the activity of thalamocortical reverberating circuits, prompted us to study the origin of the afterdischarge in the auditory cortex arising in response to single sound clicks on unanesthetized immobilized and nembutalized cats. The rhythmic afterdischarge was found to be most pronounced at light anesthesia with a tendency of background activity to synchronization, which may be evidenced by rare bursts of spindles. During the prolonged spontaneous desynchronization as well as during stimulation of mesencephalic reticular formation no rhythmic afterdischarge and no spontaneous bursts of spindles arose. With a deepening of anesthesia slow afterdischarge undergoes precisely the same changes as spontaneous spindle bursts (the duration tends to increase for a while with a subsequent decrease, the frequency and then the amplitude of waves decrease and eventually they disappear altogether). These and other findings suggest that rhythmic afterdischarge of the auditory cortex arising to sound clicks seems to be similar to the evoked spindle in response to peripheral and central stimulations. It was reported in many previous and recent papers. The fact, that following the cooling or ablation of the auditory cortex the rhythmic afterdischarge to sound clicks as well as spontaneous spindle bursts keep arising in the medial geniculate body without changing their patterns, militates also against the possibility of thalamocortical reverberation.