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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↗
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↗
PubMedDate not supplied

EEG and behavioural effects of polyamines (spermine and spermidine) on rabbits.

The EEG and behavioural changes induced by the administration of polyamines (spermine and spermidine) were studied in rabbit. Spermine and spermidine were administered at different doses (200 and 400 micrograms) into the mesencephalic ventricle (i.c.v.) both as a bolus and in constant perfusion (60 min duration). We also studied the effects of methamphetamine (MA) in a group of rabbits pretreated with spermine and spermidine 200 and 400 micrograms i.c.v. as bolus. Spermine caused a dose-related cortical synchronization associated with a partial sedation; spermidine induced cortical synchronization at a low dose without any behavioural changes while at higher dose (after perfusion) cortical desychronization with an arousal behavioural pattern occurred. The possible interaction of these substances with the mesolimbic dopaminergic system is discussed on the basis of their potential neuroleptic action.

Animals↗
PubMed1976

Synchronization of the electrocorticogram by visceral and somatic bradykinin stimulation in anesthetized cats.

The cortical response to visceral and somatic bradykinin stimulation was studied in cats under light to moderate pentobarbital anesthesia. Following the injection of bradykinin into arteries supplying visceral organs and somatic structures, a marked cortical synchronization was recorded. The bilateral, rhythmic discharge in the theta to alpha range was best seen on SI; occasionally the contralateral SI response was more prominent. The cortical synchronization and its distribution were the same for visceral and somatic stimulation. There was only minimal response desensitization to multiple injections of bradykinin in rapid succession. Following transection of the thoracolumbar spinal cord, synchronization failed to develop after hindlimb injections but continued to be seen after forelimb stimulation; similarly, partial denervation of a limb blocked the bradykinin response. No synchronization or desynchronization could be produced by epinephrine and nitroglycerine which caused phasic changes in systemic blood pressure equal to or greater than those seen with bradykinin. The results are discussed in terms of possible pathways and receptors. It is suggested that bradykinin acts primarily on free nerve endings common to visceral and deep somatic tissue with convergence of impulses occurring at spinal and higher levels. The preferential response of SI may reflect afferent activity generated by natural, painful stimulation of deep somatic and visceral organs. Normally, this component would be masked by the concomitant non-specific arousal response of the medial reticulo-thalamic system which was depressed by the anesthetic.

Afferent Pathways↗
PubMedDate not supplied

Neurobiology of the integrative activity of the brain. Dynamics of the activational and inhibitory types of synchronization of cortical neurons during the realization of a defensive reflex and of internal inhibition.

An increase in synchronization of the activational type (coincidence of the presence of impulse activity), and a decrease of the inhibitory type (coincidence of both the presence and absence of impulse activity), in the operation of close-lying neurons were observed in the visual and sensorimotor areas of the new cortex and in the hippocampus of wakeful non-immobilized rabbits in response to the combination of flashes of light with electrodermal stimulation (EDS) of the extremity. An increase in the synchronization of the neurons of the inhibitory type took place in the visual cortex in response to flashes against the background of the conditional inhibitor, i.e., continuous light, and changes in synchronization, similar to the effect of pain reinforcement but significantly weaker, appeared in the sensorimotor cortex and in the hippocampus. An increase in synchronicity of the activational type took place primarily in pairs of neurons with increase in the same direction in the frequency of impulse activity in response to a stimulus, and of the inhibitory type, took place with its decrease. In addition, both kinds of changes in synchronization appeared in a significant portion of the pairs of neurons with changes in the frequency of impulse activity of different directions.

Animals↗
PubMedDate not supplied

Comparative study of the EEG profile of neuroleptics selective for D-1 or D-2 dopamine receptors in the rabbit.

The neuroleptics SCH 23390 and raclopride, which interact selectively with either D-1 or D-2 dopamine receptor, were studied for their effects on electroencephalographic (EEG) activity in the rabbit. Haloperidol (0.3 and 1 mg/kg intravenously, i.v.), which was used for comparison, induced synchronization of the cortical EEG activity. Spectral EEG analysis showed increase of power in the whole frequency range (0.1-38.5 Hz) and in all frequency bands in the cortex, whereas a slight decrease of slow and fast theta activity (3.7-7.2 and 7.2-12.2 Hz) was observed in the hippocampus. Animals appeared sedated and arousal response to somatosensory stimuli was markedly inhibited. SCH 23390 (0.03 and 0.3 mg/kg i.v.) induced periods of cortical synchronization and changes of spectral power qualitatively similar to those accompanying haloperidol administration. The drug slightly reduced the duration of arousal elicited by stimuli. Raclopride (1 and 3 mg/kg i.v.) induced weak EEG changes and little effect on arousal response to stimulation. There was an increase of slow wave activity which was particularly evident in the hippocampus. The data indicate that, although to a lesser degree, the D-1 receptor antagonist SCH 23390 induced EEG effects similar to those of haloperidol, whereas blockade of D-2 receptors by raclopride resulted in different patterns of EEG activity.

Animals↗
PubMed1991

Network modulation of a slow intrinsic oscillation of cat thalamocortical neurons implicated in sleep delta waves: cortically induced synchronization and brainstem cholinergic suppression.

A slow (0.5-4 Hz) oscillation of thalamic neurons was recently described and attributed to the interplay of two intrinsic currents. In this study, we investigated the network modulation of this intrinsic thalamic oscillation within the frequency range of EEG sleep delta-waves. We performed intracellular and extracellular recordings of antidromically identified thalamocortical cells (n = 305) in sensory, motor, associational, and intralaminar nuclei of anesthetized cats. At the resting membrane potential, Vm (-60.3 +/- 0.4 mV, mean +/- SE), cortical stimulation induced spindle-like oscillations (7-14 Hz), whereas at Vm more negative than -65 mV the same stimuli triggered an oscillation within the EEG delta-frequency (0.5-4 Hz), consisting of low-threshold spikes (LTSs) followed by after hyperpolarizing potentials (AHPs). The LTS-AHP sequences outlasted cortical stimuli as a self-sustained rhythmicity at 1-2 Hz. Corticothalamic stimuli were able to transform subthreshold slow (0.5-4 Hz) oscillations, occurring spontaneously at Vm more negative than -65 mV, into rhythmic LTSs crowned by bursts of Na+ spikes that persisted for 10-20 sec after cessation of cortical volleys. Cortical volleys also revived a hyperpolarization-activated slow oscillation when it dampened after a few cycles. Auto- and crosscorrelograms of neuronal pairs revealed that unrelated cells became synchronized after a series of corticothalamic stimuli, with both neurons displaying rhythmic (1-2 Hz) bursts or spike trains. Since delta-thalamic oscillations, prevailing during late sleep stages, are triggered at more negative Vm than spindles characterizing the early sleep stage, we postulate a progressive hyperpolarization of thalamocortical neurons with the deepening of the behavioral state of EEG-synchronized sleep. In view of the evidence that cortical-elicited slow oscillations depend on synaptically induced hyperpolarization of thalamocortical cells, we propose that the potentiating influence of the corticothalamic input results from the engagement of two GABAergic thalamic cell classes, reticular and local-circuit neurons. The thalamocorticothalamic loop would transfer the spike bursts of thalamic oscillating cells to cortical targets, which in turn would reinforce the oscillation by direct pathways and/or indirect projections relayed by reticular and local-circuit thalamic cells. Stimulation of mesopontine cholinergic [peribrachial (PB) and laterodorsal tegmental (LDT)] nuclei in monoamine-depleted animals had an effect that was opposite to that exerted by corticothalamic volleys. PB/LDT stimulation reduced or suppressed the slow (1-4 Hz) oscillatory bursts of high-frequency spikes in thalamic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMedDate not supplied

[Effect of stimulation of the mediodorsal nucleus of the thalamus on the synchronous flow of cortical electrical processes].

It was shown in chronic experiments on rabbits that stimulation of the mediodorsal thalamic nucleus brings about, as a rule, en enhancement of amplitudes of the spatially-synchronous cortical theta-rhythm and a decreased frequency of its oscillations. Analysis of the phenomenon by means of a simple mathematical models shows that such a connection between amplitude and frequency EEG parameters may be accounted for by the existence of two-way cyclic interactions between the cortex and the thalamus, forming a closed contour of a feedback connection. The capacity of the mediodorsal thalamic nucleus to influence the synchroneity of cortical electrical processes is compared with published data on its role in conditioned activity.

Animals↗
PubMed1979

The effect of high mesencephalic transection (cerveau isolé) and pentobarbital on basal forebrain mechanisms of EEG synchronization.

A study was made of the effects of high mesencephalic transection (cerveau isolé) and low doses of pentobarbital on the cortical synchronizations elicited in acute immobilized cats by (a) low frequency stimulation of the lateral hypothalamus (HL) and nucleus ventralis anterior thalami (VA) and (b) by low and high frequency stimulation of the laterobasal preoptic region (RPO) and olfactory tubercle (TbOf). The results obtained were as follows: (1) The synchronizations induced by basal forebrain stimulations were found to survive in acute cerveau isolé cats, moreover, even a facilitation of the synchronizing effect were observed. (2) A gradual facilitation was observed upon TbOf and RPO stimulation, while in the case of VA and HL stimulations, the facilitation appeared immediately after the transection. (3) Low doses of pentobarbital depressed the cortical effects of TbOf stimulation, while an increase of the synchronizing effect of low frequency VA and HL stimulation was found. The observations suggested that (i) the synchronizing mechanism in the ventral part of the basal forebrain (RPO and TbOf) differs from that of the thalamus and HL; (ii) the basal forebrain synchronizing mechanism is effective without the contribution of the brain stem; (iii) the mechanism responsible for the synchronizing effect of low frequency HL stimulation is similar as that described for the thalamus.

Animals↗
PubMed1975

The effects of serotonin injections into the locus coeruleus on ponto geniculo occipital (PGO) waves and cortical EEG pattern in cats.

Reserpine injected iv at 0-8--1-0 mg/kg doses induced continuous ponto-geniculo-occipital (PGO-like) waves in immobilized cats. Both 5-HT and quipazine injected into the locus coeruleus decreased the frequency of reserpine-induced PGO waves and increased cortical synchronization. Suppression of PGO activity persisted for 15--30 min whilst synchronizing effects lasted much longer. Methysergide increased the frequency of PGO activity but caused no clear changes in the EEG pattern.

Animals↗