Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cortical Synchronization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed1979

[Clinical electroencephalographic characteristics of the phasic nature of the course of severe cerebrocranial injury].

In order to early recognize intracranial hematomas and contusions, differential diagnostic criteria for analysis of neurological symptomatology and EEG signs are considered from the standpoint of a phasic clinical progress of traumatic pathological conditions of the brain. The EEG syndromes of initial, pronounced and gross synchronization correlated with the clinical phases of subcompensation, mild and deep decompensation. The study demonstrates a contrary trend in the dynamics of the clinical and EEG data in compression and contusion of the brain.

Brain Concussion↗
PubMed1982

Cross-correlation analysis of midbrain reticular neuron pairs during sleep-waking cycle of the cat.

By simultaneously inserting three extracellular microelectrodes, separated by 1.0 mm from each other, into the cat's midbrain reticular formation (MRF), temporal cross-correlation of firing of neuron pairs was measured to investigate the mode of interaction among the MRF neurons during different states of sleep and wakefulness. None of 97 neurons pairs studied gave clear-cut cross-correlograms suggesting cascade connection between two neurons. However, 29 neuron pairs showed weakly synchronized firing which occurred periodically with a mean interval of 1.23 s. This interval was different from the respiratory cycle. The rhythmic synchronization appeared most obviously during slow wave sleep. The synchronized firing was encountered more often in the pairs of adjacent neurons picked up with a single electrode and in the pairs picked up with separate electrodes positioned along the mediolateral axis, when compared with the neuron pairs located along the rostrocaudal axis. About 80% of the neurons (37 our of 46) which showed periodically synchronized discharge had no corresponding periodicity in their auto-correlograms. Simple synaptic linkage conceivable for the observed periodic synchronization of a neuron pair would be shared inhibition with the common inhibitory source activated periodically. Some neurons in the dorsal raphe nucleus and in the solitary tract nucleus were also examined for the cross-correlation with the MRF neurons. However, no positive relationship was found.

Animals↗
PubMedDate not supplied

[Interrelationship between spatial synchronization and rhythmic components of the human EEG].

The main object of the work was to elucidate the functional significance of different human EEG rhythms. Cross-correlation and spectral characteristics at the background and during mental work were studied in thirteen subjects by recording from four points of the left hemisphere. During intellectual load, spatial synchronization is enhanced between the biopotentials of most areas: interrelations between remote points are intensified which leads to the smoothing of the synchronization gradient existing in a state of rest. The alpha-rhythm becomes less pronounced everywhere in parallel to the decrease in synchronism of its fluctuations in different zones; at the same time low-frequency activity (delta-theta) increases both by the amplitude of oscillations and the capacity for its unidirectional shifts over the whole cortex. The least distinct change is observed in the beta-rhythm.

Adolescent↗
PubMed2000

Relative electroencephalographic desynchronization and synchronization in humans to emotional film content: an analysis of the 4-6, 6-8, 8-10 and 10-12 Hz frequency bands.

The reactivity of different narrow electroencephalographic (EEG) frequencies (4-6, 6-8, 8-10 and 10-12 Hz) to three types of emotionally laden film clips (aggressive, sad, neutral) were examined. We observed that different EEG frequency bands responded differently to the three types of film content. In the 4-6 Hz frequency band, the viewing of aggressive film content elicited greater relative synchronization as compared the responses elicited by the viewing of sad and neutral film content. The 6-8 Hz and 8-10 Hz frequency bands exhibited reactivity to the chronological succession of film viewing whereas the responses of the 10-12 Hz frequency band evolved within minutes during film viewing. Our results propose dissociations between the responses of different frequencies within the EEG to different emotion-related stimuli. Narrow frequency band EEG analysis offers an adequate tool for studying cortical activation patterns during emotion-related information processing.

Adult↗
PubMed1997

Theta synchronization and alpha desynchronization in a memory task.

In the present study, we examined the hypothesis that episodic encoding and retrieval processes are primarily reflected by a task-related increase in theta power. Individuals performed a recognition task with a total of 192 words. The electroencephalogram was recorded during the study and recognition phase. The results show that only those words that were later correctly recognized produced a significant increase in theta power during encoding. During the actual recognition processes too, a significant theta synchronization (increase in band power) was found for correctly remembered words only. In contrast to the theta band, remembered and not remembered words revealed a complex pattern of desynchronization in the lower and upper alpha band that was different during encoding and recognition.

Adult↗
PubMed2004

Bilateral control and interhemispheric coordination in the avian song motor system.

Birdsong is a complex learned motor behavior controlled by an interconnected network of vocal control nuclei that are present in both cerebral hemispheres. Unilateral lesions of song nuclei in the left or the right hemisphere result in different effects on song structure, suggesting that normal song output results from the activation of two parallel but functionally different motor pathways. Because each syringeal half is innervated primarily by ipsilateral motor structures and activity in both halves is tightly coordinated during singing, motor commands originating from both hemispheres must be tightly coordinated to produce the appropriate vocal output. This coordination occurs despite the absence of direct interhemispheric connections between song control nuclei. In this article, we discuss how motor commands in nucleus HVC, a key forebrain song control region, are coordinated by precisely timed inputs that act to synchronize premotor activity in both hemispheres. Synchronizing inputs are tightly linked to syllable and note onset, which suggests that bilaterally organized circuits in the midbrain or brainstem act in specifying higher-order song features, such as duration, order, and possibly even structure of individual song syllables. The challenge ahead lies in identifying the networks that generate the synchronizing timing inputs and to determine how these inputs specify the motor commands in HVC. Resolving these issues will help us gain a better understanding of how pattern-generating networks in the midbrain/brainstem interface with forebrain circuits to produce complex learned behaviors.

Animals↗
PubMed1975

Analysis of various factors involved in EEG synchronization during milk drinking in the cat.

Electroencephalographic (EEG) and multineuronal activity (MUA) from several brain structures were recorded in 11 adult cats during milk drinking. Milk drinking elicited parietal and hippocampal EEG synchronization and inhibited multiunit discharge in several brain regions. The proportion of EEG synchronization varied considerably between animals, but remained more or less constant for each cat after several testing days. Neither modification of milk concentration nor fasting influenced the proportions of EEG synchronization during milk drinking. Adaptation of the animals to the experimental environment facilitated the appearance of EEG synchronization during milk drinking. Chlorpromazine (3 mg/kg) significantly increased the proportion of EEG synchronization observed during milk drinking. By contrast, displacement of the head, neck or postural body adjustments during milk drinking blocked EEG synchronization. Amphetamine also had a suppressive effect on the EEG parietal and hippocampal synchronic activity observed during milk drinking. Our results suggest that development of parietal EEG synchronization in response to pleasant stimulation is a complex phenomenon requiring a relaxed condition of the animal, including its adaptation to the experimental environment and relative immobility with the concomitant diminution of afferent inflow from some of the muscles involved in locomotion.

Amphetamine↗
PubMed2005

Phase synchronization between alpha and beta oscillations in the human electroencephalogram.

Coordination of neuronal oscillations generated at different frequencies has been hypothesized to be an important feature of integrative brain functions. The present study aimed at the evaluation of the cross-frequency phase synchronization between electroencephalographic alpha and beta oscillations. The amplitude and phase information were extracted from electroencephalograms recorded in 176 healthy human subjects using an analytic signal approach based on the Hilbert transform. The results reliably demonstrated the presence of phase synchronization between alpha and beta oscillations, with a maximum in the occipito-parietal areas. The phase difference between alpha and beta oscillations showed characteristic peaks at about 2 and -1 radians, which were common for many subjects and electrodes. A specific phase difference might reflect similarity in the organization and interconnections of the networks generating alpha and beta oscillations across the entire cortex. Beta oscillations, which are phase-locked to alpha oscillations--alpha-synchronous beta oscillations--were largest in the occipito-parietal area with a second smaller maximum in the frontal area, thus demonstrating a topography, which was different from the conventional alpha and beta oscillations. The strength of the alpha-synchronous beta oscillations was not exclusively defined by the amplitude of the alpha rhythm indicating that they represent a distinct feature of the spontaneous electroencephalogram, which allows for a refined discrimination of the dynamics of beta oscillations.

Action Potentials↗
PubMed2004

Synchronized oscillations at alpha and theta frequencies in the lateral geniculate nucleus.

In relaxed wakefulness, the EEG exhibits robust rhythms in the alpha band (8-13 Hz), which decelerate to theta (approximately 2-7 Hz) frequencies during early sleep. In animal models, these rhythms occur coherently with synchronized activity in the thalamus. However, the mechanisms of this thalamic activity are unknown. Here we show that, in slices of the lateral geniculate nucleus maintained in vitro, activation of the metabotropic glutamate receptor (mGluR) mGluR1a induces synchronized oscillations at alpha and theta frequencies that share similarities with thalamic alpha and theta rhythms recorded in vivo. These in vitro oscillations are driven by an unusual form of burst firing that is present in a subset of thalamocortical neurons and are synchronized by gap junctions. We propose that mGluR1a-induced oscillations are a potential mechanism whereby the thalamus promotes EEG alpha and theta rhythms in the intact brain.

Action Potentials↗
PubMed2000

Theta synchronization predicts efficient memory encoding of concrete and abstract nouns.

Functional and topographical differences between processing of spoken nouns which were remembered or which were forgotten were shown by means of EEG coherence analysis. Later recalled nouns were related with increased neuronal synchronization (= cooperation) between anterior and posterior brain regions regardless of presented word category (either concrete or abstract nouns). However, theta coherence exhibited topographical differences during encoding of concrete and abstract nouns whereby former were related with higher short-range (mainly intrahemispheric), later with higher long-range (mainly interhemispheric) coherence. Thus, theta synchronization possibly is a general phenomenon always occurring if task demand increases and more efficient information processing is required. Measurement of EEG coherence yields new information about the neuronal interaction of involved brain regions during memory encoding of different word classes.

Adult↗
PubMed1994

Endoglycoceramidase treatment inhibits synchronous oscillations of intracellular Ca2+ in cultured cortical neurons.

Gangliosides are major components of nerve cell membranes and are especially rich in synaptic areas. In order to evaluate the role of endogenous gangliosides in synapse formation, endoglycoceramidase (EGCase) was used to remove oligosaccharides of gangliosides from the cell surface. We have reported previously that synapse formation between cultured rat cerebral cortical neurons can be estimated by the synchronous oscillation of synaptic activity monitored by fura-2 calcium imaging. Continuous application of endoglycoceramidase (EGCase) together with its activator protein dose-dependently decreased the frequency of synchronous oscillations without any morphological changes in neurons and their neurites. The result suggests that oligosaccharides liberated from glycosphingolipids on cultured cortical cell surface with EGCase are important for synapse formation between cortical neurons.

Animals↗
PubMed1998

Effect of environmental sound familiarity on dynamic neural activation/inhibition patterns: an ERD mapping study.

The aim of this study was to analyze the timing and topography of brain activity in relation to the cognitive processing of different types of auditory information. We specifically investigated the effects of familiarity on environmental sound identification, an issue which has been little studied with respect to cognitive processes, neural substrates, and time course of brain activity. To address this issue, we implemented and applied an electroencephalographic mapping method named event-related desynchronization, which allows one to assess the dynamics of neuronal activity with high temporal resolution (here, 125 ms); we used 19 recording electrodes with standard positioning. We designed an activation paradigm in which healthy subjects were asked to discriminate binaurally heard sounds belonging to one of two distinct categories, "familiar" (i.e., natural environmental sounds) or "unfamiliar" (i.e., altered environmental sounds). The sounds were selected according to strict preexperimental tests so that the former should engage greater semantic, and the latter greater structural, analysis, which we predicted to preferentially implicate left posterior and right brain regions, respectively. During the stimulations, significant desynchronizations (thought to reflect neuronal activations) were recorded over left hemisphere regions for familiar sounds and right temporofrontal regions for unfamiliar sounds, but with only few significant differences between the two sound categories and a common bilateral activation in the frontal regions. However, strongly significant differences between familiar and unfamiliar sounds occurred near the end of and following the stimulations, due to synchronizations (though to reflect deactivations) which appeared over the left posterior regions, as well as the vertex and bilateral frontal cortex, only after unfamiliar sounds. These unexpected synchronizations after the unfamiliar stimuli may reflect an awareness of the unfamiliarity of such sounds, which may have induced an inhibition of semantic and episodic representations because the latter could not be associated with meaningless sounds.

Arousal↗
PubMed2006

Factors affecting phase synchronization in integrate-and-fire oscillators.

Step changes in input current are known to induce partial phase synchrony in ensembles of leaky integrate-and-fire neurons operating in the oscillatory or "regular firing" regime. An analysis of this phenomenon in the absence of noise is presented based on the probability flux within an ensemble of generalized integrate-and-fire neurons. It is shown that the induction of phase synchrony by a step input can be determined by calculating the ratio of the voltage densities obtained from fully desynchronized ensembles firing at the pre and post-step firing rates. In the limit of low noise and in the absence of phase synchrony, the probability density as a function of voltage is inversely proportional to the time derivative along the voltage trajectory. It follows that the magnitude of phase synchronization depends on the degree to which a change in input leads to a uniform multiplication of the voltage derivative over the range from reset to spike threshold. This analysis is used to investigate several factors affecting phase synchronization including high firing rates, inputs modeled as conductances rather than currents, peri-threshold sodium currents, and spike-triggered potassium currents. Finally, we show that without noise, the equilibrium ensemble density is proportional to the phase response curve commonly used to analyze oscillatory systems.

Action Potentials↗
PubMed2002

Effects of picture repetition on induced gamma band responses, evoked potentials, and phase synchrony in the human EEG.

Repeated experience with an object due to prior exposure to that object is commonly referred to as perceptual or repetition priming. One possible neuronal mechanism for repetition priming is 'repetition suppression' within a cell assembly coding the stimulus. Recently, induced gamma band responses (GBRs) were discussed as a possible physiological correlate of activity in such a cell assembly. The present EEG study was designed to investigate the modulation of induced GBRs when line drawings were presented either once or consecutively two or three times. Results showed a broad distribution of spectral gamma power and synchrony after initial picture presentation. Repeated presentations of the same picture led to a decrease of induced gamma power and less synchronized activity between distant electrode sites. The decrease of induced GBRs and synchrony after repeated picture presentations may be linked to a 'neural savings' mechanism within a cell assembly representing an object. Furthermore, the visual evoked potential, which was modulated by priming, showed a topographically different distribution compared to induced GBRs.

Adult↗
PubMed2006

[Changes in EEG-complexity after subcortical ischemic brain damage].

INTRODUCTION: Complexity analysis of the EEG is a relatively new field in theoretical and clinical electrophysiology. The authors present results of EEG-analysis in a patient with stroke, utilizing the sensitivity of the new procedures with respect to linear and nonlinear synchronization. PARTICIPANTS AND METHODS: The EEG (19 channels) was recorded in a patient with subcortical unilateral ischaemic completed stroke involving the frontoparietal white matter while leaving the cortex intact and in 12 healthy controls in eyes open and in eyes closed conditions. RESULTS: In the patient, increased Omega-complexity was found in slow (delta, theta) and lower alpha frequencies in the side of the stroke and in high frequencies (beta2 in eyes closed, alpha2, beta1 and beta2 in eyes open conditions) in the intact side. Synchronization likelihood was higher in the ischaemic side in the beta2 (eyes closed) and both in the beta1 and beta2 (eyes open) frequencies. Increasing Omega-complexity caused by eyes opening was markedly reduced in the patient in the beta frequencies compared to that seen in the controls. The difference was more conspicuous in the side of the infarct and involved not only the beta but also the alpha frequencies as well. Opening the eyes decreased synchronization likelihood in all frequency bands in the controls and also in the patient except the alpha2, beta1 and beta2 bands in the side of the lesion. CONCLUSIONS: The increased Omega-complexity and decreased synchronization likelihood in the slow frequencies in the infarcted side is probably the result of lesioned interneuronal connections lowering the level of cooperation of neuronal systems involved in this type of activity. The increased Omega-complexity and decreased synchronization likelihood caused by eyes opening could not be observed in the beta and alpha frequencies in the side of the lesion, possibly caused by damaged thalamocortical connections.

Alpha Rhythm↗
PubMed2004

Multifocal renal cortical tumors: frequency, associated clinicopathological features and impact on survival.

PURPOSE: We determined the frequency of tumor multifocality in patients with renal cortical tumors, characterized clinical and pathological features associated with multifocality and evaluated its effect on patient survival. MATERIALS AND METHODS: Between July 1989 and July 2002, 1,071 radical nephrectomies were performed at our institution. Specimens were examined grossly and microscopically for multifocal tumors. Preoperative imaging was reviewed to determine whether multifocality was suspected prior to operation. Multivariate analysis was performed to identify clinical and pathological factors associated with multifocality. RESULTS: Of 1,071 radical nephrectomy specimens 57 (5.3%) had pathological evidence of tumor multifocality. Bilateral synchronous renal cortical tumors were present in 6 of the 57 multifocal cases (11%). A total of 19 cases (33%) had evidence of multifocality on preoperative imaging and, therefore, occult multifocality undetected on preoperative imaging was present in 3.5% of radical nephrectomies (38 of 1,071). Primary tumors in the multifocal group were most commonly conventional clear cell carcinoma, followed by papillary carcinoma. Of multifocal cases 74% had the same histological subtype in all tumors. Multivariate analysis demonstrated that bilaterality, papillary subtype, advanced tumor stage and lymph node metastasis were associated with multifocality. At a median follow up of 40.5 months overall survival, disease-free survival, and disease-free probability were not significantly different between the multifocal and unifocal groups. CONCLUSIONS: We report a 5.3% frequency of multifocal renal cortical tumors and a 3.5% frequency of clinically unsuspected multifocal tumors. Multifocality had no apparent effect on recurrence or survival in patients who underwent radical nephrectomy.

Adolescent↗
PubMedDate not supplied

The effects of high-frequency microstimulation of the cortex on interhemisphere synchronization in the rat motor cortex.

Studies were carried out on long-term changes in the synchronization of neuronal activity in networks including callosal cells of the opposite hemispheres evoked by high-frequency microstimulation in the motor cortex of anesthetized rats. The level of synchronization was assessed in terms of the amplitude and width of peaks located symmetrically on cross-correlograms relative to the coordinate origin. Tetanization predominantly decreased synchronization in a group of initially background-active neurons, while there was a significant number of synchronously firing neurons in a group of cells which became activated. "Super-narrow" peaks appeared in interhemisphere interactions. There was a correlation between the type of modification of "narrow" (<20 msec) and "intermediate" (30-80 msec) peaks and changes in the efficiencies of mono- and polysynaptic connections.

Animals↗
PubMed2002

Widespread activation of the brainstem preceding the recruiting rhythm in human epilepsies.

The excitability change of the brainstem was investigated before and during the conspicuous epileptic discharge in six patients with generalized convulsive seizures. The discharge consisted of a short duration of recruiting rhythm, which was considered equivalent to the seizure discharge on electroencephalogram. The excitability of the brainstem was measured with the parameters (amplitude and area) of component waves (wave-III and -V) of brainstem auditory evoked potentials. The theoretical background of the analysis is that brainstem auditory evoked potentials are 'far-field' potentials, by which they convey the information on the activity change of the brainstem even during the paroxysmal discharge within the cortex. The excitability of both the ventral (parameters of wave-III) and the dorsal brainstem (parameters of wave-V) exhibited a synchronized change (activation-inactivation). They were enhanced from -2.4+/-0.4 s, reaching the maxima before the onset of the seizure discharge, and decayed corresponding to the emergence of the recruiting rhythm. The results suggest the possibility that the widespread (ventral and dorsal) and synchronized activation of the brainstem triggers the seizure discharge in human generalized epilepsy. During the widespread activation of the brainstem, both the thalamus and the cortex probably undergo a suppressed inhibitory state through the cholinergic activation, precipitating the seizure discharge.

Acoustic Stimulation↗