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 1,639 records · Page 91Linked to original sources
PubMed1978

[Evoked brain stem potentials. Study of their adaptation in multiple sclerosis].

This study of the Brainstem evoked Response has been done to try to find the exact location of neurologic disorders. The authors wanted to see if there were differences between normal subjects and patients with multilocular sclerosis, when the auditory stimulus in increasing from 10 pps to 50 pps. From 15 normal subjects (30 ears) the results have been compared to those obtained from 6 patients. The findings were: -- there is no adaptation phenomenon in the Brainstem (the conduction time in the Brainstem is absolutely constant). -- there is an adaptation which occurs before the first peak, happening later at 50 pps than at 10 pps. -- in the multilocular sclerosis the findings were: augmentation of the peak to peak delay no synchronisation of the peaks so that is very difficult to recognize each peaks. And the peaks are easier to recognize at 50 pps than at 10 pps which fact unexpectable. This dyssynchronisation at the compression and rarefaction click is for the authors an important factor for the multilocular sclerosis diagnosis.

Adult↗
PubMed1994

[The neurophysiological correlates of the processes of decision making in the cerebral cortex during visual recognition in monkeys].

In behavioral experiments on monkeys tested for a delayed visual differentiation of different colours stimuli, neuronal pools were recorded simultaneously in the visual, prefrontal and inferotemporal cortex. Wrong motor responses were always followed by considerable readjustments of the unit activity patterns whereas in right decisions a synchronisation and a cross-correlation occurred between neuronal pools. Possible mechanisms of the decision making and the reasons for the desynchronisation in wrong responses, are discussed.

Acoustic Stimulation↗
PubMed1978

Effects of sleep deprivation on awakening thresholds and sensory evoked potentials in the rat.

The EEG desynchronization response to stimuli presented during slow-wave sleep was studied in 25 chronically implanted rats after 12 hr of sleep deprivation and during control periods of normal sleep. Compared to normal sleep, sleep after deprivation was accompanied by a significant decrease in the number of EEG desynchronization responses to auditory stimuli and by an additional disproportionate decrease in the number of sustained desynchronization responses. Thalamic auditory evoked potentials were not reduced in amplitude during postdeprivation sleep, thus the decrease in number of EEG desynchronization responses to the auditory stimuli was apparently not mediated by decreased responsiveness in the peripheral auditory system. On the other hand, postdeprivation sleep was not accompanied by any significant change in total number of EEG desynchronization responses to direct trigeminal nerve stimulation nor by any change in the duration of responses to trigeminal stimulation. The results suggest that recovery from sleep loss in accompanied not by a nonspecific increase in the threshold for arousal per se but instead by a selective increase in the threshold for arousal to certain classes of peripheral stimuli.

Acoustic Stimulation↗
PubMed1994

[Observation of electroencephalogram spectrum changes over one year of Qigong training].

Using spectrum analysis method, the electroencephalogram (EEG) changes of the students who first learned Zhanzhuang Qigong in comparing with the students who did not practice at all were observed, over a period of one year. The results showed that the spectrum of EEG did not change significantly after half year training, but one year later, the alpha index of right frontal and right temporal regions decreased significantly (P < 0.05), and the beta index of right frontal and right temporal regions decreased significantly (P < 0.05). It was indicated that there was a higher tendency of EEG synchyonization, the brain activity changed from "active" to "harmonious" and "calm". It was a gradually adjusting process.

Adolescent↗
PubMedDate not supplied

[The neurochemical mechanisms of the influence of the posterior hypothalamus on the electrical activity of the forebrain hemispheres and on autonomic reactions in hens].

Effects of i.v. administration of N- and M-cholinergic blocking agents ganglerone and atropine and alpha- and beta-adrenergic blocking agents phentolamine and obsidan (propranolol) on reaction of desynchronisation of EEG and on autonomic reactions (arterial blood pressure, heart and respiratory rates) evoked by low- and high frequency stimulation of the posterior hypothalamus were studied in hens. It was shown that atropine induces a pharmacological dissociation of ascending and descending influences of the hypothalamus by blocking the desynchronizing mechanisms of the upward discharge of the hypothalamus without any apparent changes of autonomic reactions. It was found that the effects of adrenoblocking agents are diametrically opposite to that of atropine in regard to the EEG component, as well as the autonomic components of hypothalamically induced activation reaction. Peculiarities of evolutionary development of neurochemical structures of ascending and descending systems of the hypothalamus are discussed.

Animals↗
PubMedDate not supplied

Electrocortical desynchronization after microinfusion of kainic acid into the locus coeruleus in rats.

Receptors for the endogenous excitatory amino acid, 1-glutamate, occur in the rat locus coeruleus (LC), an area of the brain involved in the control of sleep/arousal mechanisms and other behavioral functions. However, the functional role of this neurotransmitter system in the LC has yet to be clarified. Therefore, to address this question we have studied the gross behavioral changes and the effects on the electrocortical (ECoG) spectrum power in rats receiving focal injections into the LC of kainic acid, an agonist at the non-N-methyl-D-aspartate (non-NMDA) glutamate receptor subtype. Unilateral injection of kainic acid (25, 50, 100 and 200 pmol) into the rat LC produced contralateral turning, circling and stereotypes; these effects were accompanied by dose-dependent ECoG desynchronization and by a significant decrease in total voltage power and in 6-9, 9-12 and 12-16 Hz bands of the ECoG spectrum. A pretreatment (15 min before) with 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX) (50 and 100 pmol), a competitive non-NMDA receptor antagonist, or with dizocilpine meleate (MK-801) (1 pmol) and 3-(2-carboxy-piperazine-4-yl)-1-propenyl-1-phosphonic acid) (CP-Pene) (10 pmol), two selective NMDA receptor antagonists, injected directly into the LC, abolished the behavioral and ECoG spectrum power effects typically elicited by kainic acid (50 pmol). Similar results were observed in rats pretreated with diazepam (0.5 mg/kg given i.p. 15 min before kainic acid).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[A coherent EEG analysis in the trace processes of "animal hypnosis" in rabbits].

Dynamics of structural changes of coherent relations between electrical activity of sensorimotor and premotor cortical areas of both cerebral hemispheres during and after "animal hypnosis" was studied by spectral-correlative analysis in rabbits. It was shown that "animal hypnosis" had very long-lasting trace processes, i.e., hypnotic structure of coherent relations of electrical activity in the cerebral cortex was maintained during several days. During and after a hypnotic episode interhemispheric asymmetry of electrical activity arose being more expressed in the delta-range in the left hemisphere. "Centers of animal hypnosis" were able to sum not only the effects of repeated hypnotic episodes but also excitation induced by sound stimuli immediately after hypnotic period and in the following days. Focus of stable activity with dominant properties was formed in CNS during "animal hypnosis".

Acoustic Stimulation↗
PubMedDate not supplied

[A coherence analysis of the electrical activity of the rabbit brain with a hunger dominant].

Hunger dominant was created in daily (for 24 hours) food deprived rabbits. The presence of summation was judged by the appearance of the swallowing of the chewing movements in response to sound. At creation of the hunger dominant the coherence (Cog) of the electrical activity of the sensorimotor, frontal, and parietal areas of the cerebral cortex raised. There established the differently directed Cog of the potentials of the lateral (LH), medial (VmH) hypothalamus and the cortex, especially regular in the delta- and the theta-bands. Cog between the potentials of the LH and the cortex lowered, and Cog between that of the VmH and the cortex, on the contrary, raised. There appeared a certain mosaic of coherent connections of the hypothalamic electrical processes: Cog between the potentials of the LH and the VmH raised and Cog between that of the medial and lateral preoptic areas lowered.

Animals↗
PubMedDate not supplied

[The electroencephalographic correlates of the intellectual abilities of adolescents].

Analysis of correlation between intellectual faculties of schoolchildren and spatiotemporal organization of their brain electrical activity was carried out. The less intelligent teen-agers showed more expressed alpha-activity in the EEG of rest, higher level of EEG coherence, and insignificant restructuring of the rhythmical activity under conditions of "open eyes" as compared with the "closed eyes". In the resting EEG of highly intelligent teen-agers beta-frequencies were more expressed and desynchronization after opening the eyes was clearly detectable.

Adolescent↗
PubMed1996

Electrocorticographic desynchronization after application of visceral and somatic noxious stimuli in urethane-anesthetized rats: effect of intrathecal administration of tachykinin (NK 1 or NK 2) receptor antagonists.

We investigated the electrocortical (E.Co.G) correlates of visceral (topical capsaicin application or overdistension of the urinary bladder) and somatic (perineal pinching) painful stimulation in urethane-anesthetized rats and their modulation by intrathecal application of selective tachykinins receptors (NK 1 and NK 2) antagonists. Vesical overdistension or topical capsaicin on the bladder serosal surface produced an immediate and lasting E.Co.G. desynchronization resembling a cortical arousal. A second application of capsaicin was ineffective. Bladder contraction induced by topical acetylcholine did not alter E.Co.G. A desynchronized E.Co.G. was also induced by pinching of the perineal area of the rat. Intrathecal administration of lidocaine at lumbosacral level abolished the E.Co.G. desynchronization induced by both visceral and somatic noxious stimulation. On the other hand capsaicin-induced or over-distension (but not pinching-induced) E.Co.G. desynchronization disappeared in animals systemically pretreated with capsaicin or after intrathecal administration of NK 1 tachykinin receptor antagonists such as the peptide GR 82334 or the nonpeptide RP 67580, whereas the inactive enantiomer RP 68651 or the nonpeptide NK 2 antagonists SR 48968 were ineffective. In conclusion, the experimental model described herein, allowing a quantitative analysis of the E.Co.G. correlates of visceral and somatic noxious stimulation in urethane-anesthetized rats, provides evidence for a specific neural pathway carrying bladder-arising visceral (both mechanical and chemical) nociception that uses pelvic capsaicin-sensitive afferents projecting to NK 1 (but not NK 2) bearing spinal neurons and that ultimately leads to activation of cortical areas.

Acetylcholine↗
PubMed1995

Resonant cell assemblies: a new approach to cognitive functions and neuronal synchrony.

This paper presents a novel reading of ideas on temporal binding as a key for cognitive operations by means of fast (gamma band) phase synchrony. We advocate a view of binding of widely distributed cell assemblies transiently locked in a neural hypergraph which serves as a reference point to incorporate or interpret other less coherent concurrent neural events. The paper traces in some detail the empirical evidence concerning the gamma binding process and presents some implications for the constitution of a unified cognitive-mental space.

Animals↗
PubMed1996

[Non-photic entrainment of human circadian clock--effects of forced sleep-wake schedule on the circadian rhythm in plasma melatonin].

The present study was performed in order to have better understanding of the human circadian system. Two hypotheses concerning with the human circadian system have been advanced. One is a two self-sustained oscillator hypothesis, and the other is a two process hypothesis. Both hypotheses are based on a phenomenon called internal desynchronization. A major difference between the two hypothesis is that sleep or wakefulness does not affect the circadian oscillation in the two process hypothesis, while a mutual interaction between sleep (wakefulness) and the circadian oscillation is not excluded in the two oscillator hypothesis. On the other hand, social sues such as a sleep-wake schedule and regular contact with others have been considered as a major time cues (zeitgeber) for the human circadian rhythm. However, lights brighter than 5,000 lux was recently demonstrated to be capable of resetting the human circadian rhythm, and it is now a matter of debate whether the resetting effect of social cues is due to the light-dark cycle inevitably associated with a sleep-wake schedule. In the present study, the effects of forced sleep-wake schedules on the circadian rhythm in plasma melatonin and rectal temperature were examined in subjects under temporal isolation, which are not explained by the two process hypothesis. As a result, the forced sleep-wake schedule of 24.0-hour period in dim light condition (below 200 lux) entrained the circadian rhythms in 3 out of 8 subjects. The forced schedule in extremely dim light condition (below 5 lux) was also capable of entraining the circadian rhythm. On the other hand, the forced schedule of 23.5-hour period showed no entrainability. It is concluded that the non-photic entrainment is operating in the human circadian clock, which supports the two self-sustained oscillator hypothesis.

Adolescent↗
PubMedDate not supplied

EEG-based brain computer interface (BCI). Search for optimal electrode positions and frequency components.

Several laboratories around the world have recently started to investigate EEG-based brain computer interface (BCI) systems in order to create a new communication channel for subjects with severe motor impairments. The present paper describes an initial evaluation of 64-channel EEG data recorded while subjects used one EEG channel over the left sensorimotor area to control on-line vertical cursor movement. Targets were given at the top or bottom of a computer screen. Data from 3 subjects in the early stages of training were analyzed by calculating band power time courses and maps for top and bottom targets separately. In addition, the Distinction Sensitive Learning Vector Quantizer (DSLVQ) was applied to single-trial EEG data. It was found that for each subject there exist optimal electrode positions and frequency components for on-line EEG-based cursor control.

Adult↗
PubMed1995

Orienting-like reaction after ibotenic acid injections into the thalamic centre median nucleus in the cat.

The excitotoxin ibotenic acid was injected bilaterally into the intralaminar centre median nucleus of chronically implanted cats in order to study the effects of early excitation of centre median population on electrographic correlates of behavioral states and to compare them to those induced by injection into intralaminar centralis lateralis nucleus, previously shown. Immediately and during the first 24h after injection, highly aroused behavior with electrocortical activation, myoclonic jerks, enhancement of ocular movements and ponto-geniculo-occipital waves were observed. Surprisingly, in contrast to the increase of REM sleep episodes in centralis lateralis cases, REM sleep was obliterated. The injection sites were histologically confirmed. The different connectional properties of the two intralaminar population may explain the differential results. 5. In conclusion, the present behavioral observations and electrographic findings taken together with the known afferent and efferent projections suggest that the caudal group of intralaminar nuclei is involved in orienting-like behavior.

Afferent Pathways↗