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At least 19 recordsLinked to original sources
PubMed1976

Cortical synchronization induced by thermal stimulation of the preoptic area in immobilized rats.

Cortical synchronization characterized by frontal spindles and occipital slow wave activity was induced by bilateral thermal stimulation of 2--4 degrees C of the preoptic area in unanaesthetized immobilized rats. The synchronization was demonstrated by ECoG and its power density spectra. The ECoG of the synchronization was similar to that of slow wave sleep. Switching off the thermal stimulation the original activity was recovered in most of the cases. Frontal spindle activity and slow wave activity recorded over the posterior cortex seemed to be dissociated to some degree. Low frequency stimulation at the points of thermal stimulation resulted in frequency following synchronization. In some cases electrical and thermal stimulation induced gradually developing seizure activity.

Animals↗
PubMed1976

Dependence of reward contingent positive variation (RCPV) and cortical synchronization on visual input in the cat.

Cats trained to press a lever for milk reward display high amplitude low frequency electrocorticographic post-reinforcement synchronization (PRS) associated with epicortical steady potential shift, termed Reward Contingent Positive Variation (RCPV), over the parieto-occipital cortex. Previously, it was found that the PRS-RCPV phenomenon depends on unpatterned light input devoid of any conceivable information or conditional property. Although training in the dark most likely eliminated the "novelty" factor and the resulting orienting reaction to "light off" as a cause of PRS-RCPV suppression, a possibility could not be excluded that the absence of light had a negatively reinforcing property preventing the emergence of PRS-RCPV. Hence, in the present study an experimental paradigm was used in which "light off" and/or "tone on" cues signalled the availability of reward, the "light off" periods extending through the consummatory response. Seven out of 9 cats, despite 2-4 months of daily training, and 85% correct timing of bar press performance, never showed a PRS-RCPV response (one animal showed only sporadic and poorly developed patterns.) However, when the light was turned on during consumption, in 85% of such tests a fully developed PRS-RCPV emerged in a stimulus-bound manner. One animal was an exception and showed PRS-RCPV both in the absence and presence of light. It was concluded that light input plays a crucial role in the emergence of the PRS-RCPV phenomenon and therefore also participates in the integration of gustatory input.

Animals↗
PubMedDate not supplied

[Influence of the mesencephalic reticular formation on the synchronization of cortical evoked potentials].

It has been shown in experiments on alert rabbits that evoked potentials (EP) of the visual and motor cortex to a millisecond stimulation of the midbrain reticular formation (RF) have a greater similarity (due to increased amplitude and coherence of the theta-rhythmic components) as compared with preceding background activity and evoked potentials to a photic flash. The EPs of these neocortical areas to a photic flash had a more similar form after preliminary RF stimulation. The similarity of evoked responses to stimulation of RF increased after its repeated presentations. The summate poststimulus histogram in which the responses of individual units (24 neurones) of the visual cortex to a single RF stimulation were summed up, proved to be similar in form to EP recorded on the surface of the visual cortex after a similar RF stimulation.

Animals↗
PubMed1985

Mapping of regions in the caudal brain stem that produce stimulus-bound synchronization in the cortical EEG.

This study was aimed at filling the lacunae in our knowledge regarding the localization of the regions in the caudal brain stem that bring about cortical EEG synchronization on electrical stimulation and characteristic features of synchronized waves elicited from those regions. Studies were conducted on 40 encéphale isolé cats. Stimulation of ventromedial regions of the caudal brain stem, with low frequency, elicited stimulus-bound synchronized waves in the cortex which were more prominent ispsilaterally. On the other hand, low-frequency stimulation of dorsal and lateral areas produced synchronized waves which were either equally prominent on both sides, or more prominent on the contralateral side. The loci in the brain stem that produce synchronization were very specific. The induced synchronized waves showed amplitude modulation and did not outlast the train of stimuli. The results are further confirmation of the role of caudal brain stem structures in cortical EEG synchronization. They also provide information regarding the nature of cortical synchronization elicited from these brain stem structures.

Animals↗
PubMedDate not supplied

[Effect of anodal polarization of several subcortical structures on the spatial synchronization of cortical potentials during elaboration of a defensive conditioned reflex in rabbits].

The effect of the functional state of some thalamic and hypothalamic nuclei, modified by anode polarization, on spatial synchroneity of cortical potentials (SSCP) and the speed of elaboration of a conditioned defensive reflex (CDR) were studied in chronic experiments on 15 rabbits. Reversible blockade of the studied subcortical structures considerably affected the local SSCP form and the reflex execution. In intrasignal periods the global SSCP practically did not change. A comparative analysis of the results permits an assumption that the mammillary bodies play an important role in the formation of local SSCP at the beginning of defensive conditioning and that in the stabilized reflex, this SSCP form requires the activity of non-specific thalamic nuclei.

Animals↗
PubMed1976

Changes in multiunit activity and EEG induced by the administration of natural progestins to flaxedil immobilized cats.

The effects of progesterone (P) and 7 of its metabolites on the EEG and multiunit activity (MUA) of various limbic structures were studied in flaxedil immobilized cats. Most progestins inhibited the MUA of the mesencephalic reticular formation, hippocampus and hypothalamus and induced cortical EEG synchronization. MUA changes in the mesencephalic reticular formation frequently preceded EEG synchronization. Progestins reduced in the 5 beta postition (pregnanolone, epipregnanolone and pregnanedion) inhibited neuronal discharge and synchronized EEG activity with shorter latencies and in lower doses than those reduced in the 5 alpha position (allopregnanolone and allopregnanedion). Progestins having the delta 4,3-keto structure (P, 20 alpha-hydroxy pregnenone, 20 beta-hydroxy pregnenone) induced electrophysiological changes with prolonged latencies and in doses significantly higher than ring A reduced progestins. Administration of epipregnanolone to "cerveau isole" preparations depressed neuronal firing in those structures located rostral to the level of the brain stem transection (hypothalamus, hippocampus), but failed to increase the already synchronized cortical activity. These results suggest that: a, ring A reduction increases the capacity of P and other delta 4,3-keto progestins to inhibit neuronal discharge in certain brain areas and b, changes in neuronal firing induced by progestins are not necessarily mediated through the cat brain stem reticular formation.

Animals↗
PubMedDate not supplied

[The dynamics of the activating and inhibitory types of cortical neuron synchronization during the realization of a defensive reflex and internal inhibition].

In the visual and sensorimotor areas of the neocortex and in the hippocampus of alert nonimmobilized rabbits, in response to combinations of light flashes with electrocutaneous limb stimulation an increase was observed of synchronization in the activity of the near-by neurones by activation by inhibitory type (coincidence of the presence and absence of impulse activity). In response to flashes against the light background--conditioned inhibitor--in the visual cortex synchronization of neurones increased by inhibitory type, and in the sensorimotor cortex and hippocampus changes of synchronization appeared, similar to the action of pain reinforcement but considerably weaker. The increase of synchronization by the activation type took place mainly in the neurones pairs with unidirected increase of impulses frequency and by the inhibitory one--with its decrease. Along with this, in a considerable part of neurones pairs both changes of synchronization appeared at the impulses frequency changes of different direction.

Animals↗
PubMedDate not supplied

Influence of acetylcholine on shifts in spatial synchronization of cortical potentials of the rabbit, elicited by reversible interruption of the associations of the mammillary bodies.

A decrease in 25 out of 53 calculated coefficients of linear correlation of the potentials between pickups from the visual and motor areas of the cortex, far removed from one another, was observed during anode polarization (20-30 microA, 24 min) of the mammillary nuclei, the column of the fornix, and the mammillothalamic tract, using monopolar 24-channel pickup of the potentials of the cerebral cortex in six rabbits. Application of a 1-2% solution of acetylcholine to the visual area of the cortex leads to an increase in spatial synchronization (13 out of 53 coefficients of correlation) for 5 minutes and between the 10th and 15th minutes from the start of the application. With the combined effect of the polarization of these formations and of the acetylcholine applied to the cortex, reciprocal compensation of the changes in spatial synchronization which wer elicited by each of the influences separately was observed. The hypothesis is advanced of the existence of a nonspecific cholinergic synchronizing system which is active when the mammillothalamocortical connections are preserved.

Acetylcholine↗