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Results for “Cortical Synchronization”

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At least 325 records · Page 18Linked to original sources
PubMed1993

Rhythmic and patterned neuronal firing in visual cortex.

We present evidence from multi-electrode recordings that the stimulus driven activity in a region of monkey visual cortex displays synchronous, oscillatory behaviour with temporally changing patterns of firing. The spatial-temporal patterns are dependent on cortical layer and on visual stimulus, 'build up and die down' with a period of 70-100 msec, and cannot be factorized into separate spatial and temporal components. This finding supports neural network models which explicitly incorporate spatial-temporal structure, ruling against a purely spatial code for information processing. The new type of analysis presented here is also suitable for direct on-line interactive analysis during multi-electrode recording experiments. Further, it could be modified for use in human EEG or evoked response recordings.

Action Potentials↗
PubMed1998

Effects of alpha-pompilidotoxin on synchronized firing in networks of rat cortical neurons.

We studied the effect of a novel neurotoxin, alpha-pompilidotoxin (alpha-PMTX) on the spontaneously synchronized network firing of cultured rat cortical neurons. Alpha-PMTX acted immediately and irreversibly to disrupt synchronous activity, leaving only residual sparse, uncorrelated firing and was effective at concentrations of 10 nM. In the presence of bicuculline to block inhibitory synaptic transmission, the shutdown in synchronized activity occurred with a significant delay, required a higher concentration of alpha-PMTX (> 100 nM), and was preceded by a transiently increased level of firing. It appears that both inhibitory and excitatory neuronal activity or synaptic transmission are amplified by alpha-PMTX, but that intense activity eventually leads to inactivation or transmitter depletion.

Action Potentials↗
PubMed2006

Corrective movements in response to displacements in visual feedback are more effective during periods of 13-35 Hz oscillatory synchrony in the human corticospinal system.

Oscillatory synchronization in the beta (approximately 20 Hz) band is a common feature of human motor control, manifest at cortical and muscular levels during tonic contraction. Here we test the hypothesis that the influence of visual feedback on performance in a positional hold task is increased during bursts of beta-band synchrony in the corticospinal motor system. Healthy subjects were instructed to extend their forefinger while receiving high-gain visual feedback of finger position on a PC screen. Small step displacements of the feedback signal were triggered either by bursts of beta oscillations in scalp electroencephalogram or randomly with respect to cortical beta activity, and the resulting positional corrections expressed as a percentage of the step displacement. Corrective responses to beta and randomly triggered step changes in visual feedback were 41.7+/-4.9 and 31.5+/-6.8%, respectively (P<0.05). A marked increase in the coherence in the beta band was also found between muscle activity and cortical activity during the beta-triggered condition. The results suggest that phasic elevations of beta activity in the corticospinal motor system are associated with an increase in the gain of the motor response to visual feedback during a tonic hold task. Beta activity may index a motor state in which processing relevant to the control of positional hold tasks is promoted, with behavioural consequences.

Adult↗
PubMed1979

Synchronization of EEG activity of male Rhesus monkeys Macaca mulatta treated with ovocyclin.

Bipolar stainless steel electrodes were stereotaxically implanted in hypothalamus and cortex of six male monkeys. The effect of intramuscular injection of estradiol dipropionate (ovocyclin) in a dose of 10 mg/d was observed on EEG activity on 3 successive days. On the first day, slow waves appeared only in preoptic and on the second day also in posterior hypothalamus. Generalized slowing with an increase in amplitude appeared in all the hypothalamic areas and cortex on the third day. This suggest estrogen to possess (i) cumulative effect on brain and (ii) inhibitory action in the form of synchronization of EEG activity.

Animals↗
PubMed1975

[The normal reaction of sinocarotidian origin in the rabbit].

Spontaneous changes of respiratory rate and blood pressure in the slightly anesthetized rabbit, contemporaneous with hippocampal synchronization, might be related with abrupt changes of the alertness. Registration of arousal reaction in hippocampal, thalamic and cortical leads, elicited by Hering nerve stimulation, shows that baro- and chemosensitive afferences may induce activation of areas which are usually involved in conditioning process.

Animals↗
PubMed1997

[The effect of sex on the spatial synchronization of the EEG].

The data obtained shows that women are characterised by a significantly larger interindividual variations of the EEG synchronizing than men (except the synchronizing in the left hemisphere). The findings are supposed to be due to a higher level of unspecific cortical activation in men.

Adolescent↗
PubMed2003

Gamma synchronization in human primary somatosensory cortex as revealed by somatosensory evoked neuromagnetic fields.

Cortical sensory neurons synchronize their activity at multiple frequency bands after an external stimulation. In the somatosensory cortical areas, previous reports describe more discrete and somatotopically specific neural synchronization at the gamma band. Therefore, an efficient gamma synchronization of the neurons in primary somatosensory cortex (S1) may be expected to characterize the stimulus processing from the thumb, i.e. the hand's most skillful area. To test this hypothesis, neuromagnetic fields were evoked over human S1 by the electrical stimulation of the contralateral thumb or little finger. Neuronal synchronization was indexed by the spectral coherence of the evoked neuromagnetic fields overlying S1. The frequencies of interest were the beta (16-32 Hz) and gamma (36-46 Hz) bands. The global amount of the coherence was defined as the total event-related coherence (ERCoh) among all magnetic sensors overlying the S1. Results showed prevalent increment of beta ERCoh (20-32 Hz) after the little finger stimulation and of gamma ERCoh (36-44 Hz) after the thumb stimulation. These results suggest that the neural synchronization in S1, as revealed by the ERCoh, may vary in frequency as a function of the finger stimulated. In this framework, the neural synchronization at gamma band may characterize the cortical representation of thumb, functionally prevalent with respect to little finger in humans.

Afferent Pathways↗
PubMed2000

Bimodal effects of acetylcholine on synchronized calcium oscillation in rat cultured cortical neurons.

To understand the plastic changes in neural network dynamics, we analyzed the modulating effects of cholinergic agonists on synchronized Ca(2+) oscillation in the rat primary cultured cortical neurons. At 5-10 days after establishment of the culture, neurons exhibited synchronized Ca(2+) oscillation. This Ca(2+) oscillation was derived from glutamatergic and gamma-aminobutyric acid (GABA)ergic synaptic inputs from neighboring neurons. Application of acetylcholine and nicotine increased, decreased, or did not change the frequency of synchronized Ca(2+) oscillation, depending on the colonies in the culture. The presence of cholinergic neurons in the culture was confirmed by immunocytochemical staining. Our study provided evidence for the first time that cholinergic neurons exert excitatory influences on GABAergic neurons as well as glutamtergic neurons, resulting in bimodal effects on the frequency of synchronized Ca(2+) oscillation in the cortical neural network.

Acetylcholine↗
PubMed1975

On the synchronizing effect of amantadine-1-hydrochlorid (Symmetrel) on pathological EEG-activity.

The pathological EEG of a 60 years old lady who suffered from an organic mental syndrome with parkinsonian features, showed diffuse, slow asynchroneous activity. Administration of Symmetrel repeatedly and consistently caused a normalization of the EEG, while its discontinuation immediately led to the reappearance of the original desynchronized pattern. These EEG changes were not accompanied by any modifications in the patients' clinical condition. This discrepancy between the antiparkinsonian and the synchronizing effect of Symmetrel upon the EEG can be explained by a specific activity on the reticulo-thalamo-cortical pathways in addition to that upon the nigro-striatal tracts.

Amantadine↗