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At least 163 records · Page 9Linked to original sources
PubMed2000

Intracranial EEG seizure-onset patterns in neocortical epilepsy.

PURPOSE: We investigated neocortical seizure-onset patterns recorded by intracranial EEG with regard to anatomic location, pathologic substrate, and prognostic value for surgical outcome. METHODS: Seizure onset was analyzed in 53 neocortical resective epilepsy surgery patients. Anatomic location was divided into temporal and extratemporal. Pathologic substrate was classified as developmental, mature, and negative or non-specific gliosis. Onset frequency was categorized by visual analysis into tradition EEG frequency bands. Spatial extent was divided into focal (fewer than four contacts) and regional (more than five contacts). Waveform at seizure onset was divided into several types based on their morphology. Onset features were examined with respect to anatomic location, pathologic substrate, and surgical outcome. RESULTS: Seizure-onset frequency was significantly related to spatial distribution and to anatomic location. Extratemporal and regional onset were more commonly in the gamma range, and temporal and focal onset in the beta frequency range or slower. Waveform could be categorized into five different patterns, of which low voltage fast activity (LVFA) was the most common form (57%). LVFA and rhythmic alpha-theta spike activity were more common in developmental than in mature pathology, whereas rhythmic sinusoidal waves at onset were found in only mature substrates. Waveform pattern showed a possible correlation with surgical outcome (p = 0.097): LVFA and rhythmic sinusoidal waves onset patterns were associated with favorable outcome more often (40.4%) than the other three patterns (6.3%). Slow onset suggested poor outcome in the subgroup of developmental pathology (p = 0.062). CONCLUSIONS: Certain electrographic seizure-onset features are associated with specific substrates and outcomes, whereas others reflect the anatomic location and its connections independent of the pathology.

Adolescent↗
PubMed1993

Interhemispheric electroencephalographic coherence as a biological marker in alcoholism.

Electroencephalographic coherence scores in 21 teetotaler first-degree relatives of alcoholics, 27 subjects with alcohol dependence and 21 healthy subjects without a family history of alcohol abuse were compared. The relatives had significantly higher coherence scores in the frontal and parietal leads than the alcoholics and in the frontal and centroparietal leads than in the healthy subjects. This might represent a trait marker of resilience in subjects at high risk for the development of alcoholism.

Adult↗
PubMed1992

The brain in fractal time: 1/f-like power spectrum scaling of the human electroencephalogram.

"1/f-like" power spectrum scaling is a ubiquitous feature of complex systems. In such scaling, the power spectrum of a given time series is dominated by an inverse power law, resulting in an inverse linear relation between log power and log frequency. The 1/f-like power spectrum scaling properties of human, resting eyes-closed and eyes-open EEG were examined. For both eyes-closed and eyes-open EEG, log power had a significant inverse linear relation with log frequency. The slope of this relation was not correlated with previously-calculated Grassberger-Procaccia dimension estimates for the same data, indicating that the EEG is not a 1/f-like stochastic process. Further, the degree of deviation from perfect log power versus log frequency linearity was related to power in the 8-12 Hz alpha frequency band. It is speculated that this deviation may be related to the low dimension of a chaotic alpha rhythm relative to other EEG rhythms.

Adult↗
PubMed2002

Role and limitations of routine and ambulatory scalp electroencephalography in diagnosing and managing seizures.

The scalp electroencephalogram (EEG) is the cornerstone in the diagnosis and treatment of seizure disorders. The EEG, with its excellent temporal resolution, provides a direct measurement of cortical electrophysiology, revealing, for example, the presence of interictal epileptiform discharges that identify regions of an epileptogenic brain. We define the EEG characteristics of focal and generalized epileptiform discharges and provide evidence for their varying diagnostic importance in different patient populations. Identification of nonepileptiform EEG transients, such as wicket waves, small sharp spikes,rhythmic temporal theta activity, and 14- and 6-Hz positive bursts, that can be confused for epileptiform transients is emphasized. A final point is that the clinician must interpret EEG findings within the overall clinical context.

Alpha Rhythm↗
PubMed1985

[Multiple sclerosis and the electroencephalogram (computer EEG studies)].

A computerized analysis of EEg-records from 96 multiple sclerosis (MS) patients yielded about twice as many abnormal results (79%) in comparison to the usual visual EEG-evaluation (39%). The statistically significant (p less than 0.05) increase in slow frequencies in addition to beta frequencies to the cost of alpha, but especially the reduction in total percentage of alpha contribution to overall EEG-power discriminated most efficiently between MS-patients and our normal population. Thus, alpha index alone allowed for 87% correct classification of the normal population, and 73% of patients with normal visual EEG-records were correctly classified as belonging to the MS-population. Extending the patient group to include pathological visual EEG-records as well, the corresponding figures were 95% and 89%, respectively. The computerized EEG-analysis was thus clearly superior to the usual visual inspection.

Adult↗
PubMed1982

[Effect of acute hypoxia on the EEG and neuronal pulse activity of various brain structures in rats].

The initial phase of hypoxia effect involves activation of the EEG (2000---6000 m) and unit impulse activity (7500--10 000 m). The 7500--10 000 m induced a change towards a predominant slow rhythm of the delta-type while the unit impulse activity gradually diminished, the cortical neurons displaying a higher hypoxia sensitivity and an earlier suppression than the cells of the hypothalamus and the medulla. In all phases of the hypoxia effect the EEG waves showed a greater sensitivity to the rapid peripheral signals than the unit impulse activity of the cortex and other brain structures.

Acute Disease↗
PubMedDate not supplied

[The dynamics of the dominant alpha-rhythm frequency in the perception and reproduction of time intervals].

Dependence of the dominant alpha frequency on the processes of perception and subsequent reproduction of time intervals by rhythmic hand pressing was analysed. Two groups of subjects were separated, which demonstrated either an increase (I) or a decrease (II) in the dominant alpha frequency after the transition from perception to reproduction. In the I group 83% of the subjects reproduced time intervals with a delay. In the II group reproduction in advance was observed in 75% of the subjects. The dynamics of the dominant alpha frequency probably reflects formation of the optimal functional state underlying the individual level of activation and properties of the higher nervous activity in the subjects from both groups.

Acoustic Stimulation↗
PubMed2002

Delta opioid inhibition of light-induced phase advances in hamster circadian activity rhythms.

A master neuronal pacemaker located within the suprachiasmatic nucleus in the ventral hypothalamus generates circadian activity rhythms in hamsters. The circadian pacemaker receives afferent input from many brain regions, one of which is the intergeniculate leaflet of the thalamus. This thalamic input to the suprachiasmatic nucleus in hamsters contains enkephalins, neuropeptide Y, neurotensin, and GABA. The role of enkephalins in modulating light-induced phase shifts of hamster activity rhythms has not been reported. Therefore, in this study, we examined the ability of enkephalin-mimetic and other opioid compounds to modulate light-induced phase advances in hamster circadian activity rhythms. The delta opioid agonists SNC 80 and BW373U86 both inhibited light-induced phase advances of hamster circadian activity rhythms. Neither the mu opioid agonist morphine, nor the kappa opioid agonist U50488H had any effect on light-induced phase shifts. The antagonists naltrindole, naltrexone, and nor-binaltorphimine, selective for delta, mu, and kappa opioids respectively, were also without effect on light-induced phase advances. Therefore, we found that only delta opioid agonists modulate light-induced phase advances in hamster circadian activity rhythms. These results imply that enkephalins released from the intergeniculate leaflet onto components of the suprachiasmatic pacemaker may be capable of inhibiting the responsiveness of the pacemaker to photic input arriving from the retina. The inability of antagonists to modulate light-induced phase advances suggests that endogenous opiate systems are not tonically active in generating circadian activity rhythms, but rather that enkephalins are probably used by the circadian system to modulate responses only under certain conditions or time of day.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1992

Intrinsic and synaptically generated delta (1-4 Hz) rhythms in dorsal lateral geniculate neurons and their modulation by light-induced fast (30-70 Hz) events.

Thalamocortical neurons of cat dorsal lateral geniculate nucleus were recorded under urethane anesthesia. Neurons were identified by antidromic invasion from the internal capsule and by orthodromic stimulation from the optic chiasm or light stimuli. An intrinsic oscillation within the frequency of sleep delta waves (1-4 Hz) was induced by hyperpolarizing current pulses triggering a rhythmic sequence of low-threshold spikes alternating with after hyperpolarizing potentials. The increased propensity to oscillation after blockage of inputs arising in the retina indicates that afferent synaptic drives interfere with the intrinsic oscillation of lateral geniculate cells. The relatively rare occurrence of this type of oscillation in impaled neurons, as compared with extracellular recordings in the same nucleus or to intracellular recordings in other dorsal thalamic nuclei, suggests that the interplay between the two intrinsic currents generating delta oscillation is particularly critical in lateral geniculate cells. Another type of delta oscillation was characterized by excitatory postsynaptic potentials which gave rise to action potentials or to low-threshold spikes at more depolarized or hyperpolarized levels, respectively. It is suggested that this rhythm reflects synaptic coupling by intranuclear recurrent axonal collaterals. Light stimulation induced fast (30-70 Hz) excitatory events that were blocked after lidocaine injections into the eye. In all tested cells, changes in the ambient luminosity of the experimental room blocked the intrinsic as well as the synaptic oscillation within the delta frequency. In some cells, this suppressing effect was associated with depolarization and increased firing rate. These results demonstrate different types of sleep delta oscillations in visual thalamic neurons and show that they are modulated not only by brainstem regulatory systems, but also by specific drives along the visual channel.

Animals↗
PubMed1994

Synchronized sleep oscillations and their paroxysmal developments.

The state of resting sleep is associated with a series of oscillations generated in cortical and thalamic networks. A newly discovered rhythm groups the spindle and delta sleep oscillations within slowly recurring (< 1 Hz) sequences. Multi-site, extra- and intracellular recordings provide evidence for synchronization of various classes of cell in the neocortex and thalamus during sleep oscillations that might reach paroxysmal levels similar to epileptic states. Sleep oscillations and the underlying synchronizing processes are disrupted during transition to brain arousal.

Animals↗
PubMedDate not supplied

[The effects of artificial analogue peptide TSKY isolated from the brain of hibernating ground squirrels in rats and mice].

Elevation of the i.c.v. injection dose of TSKY from 4 to 8 microg increased the movement activity of rats; in EEG theta- and beta-rhythms were enhanced and alpha-rhythm was suppressed. On the contrary, after treatment of 15 microg the rats fell into sleepy-like state; theta- and beta2-rhythms suppression, delta-, alpha- and beta1-rhythms were increased. Exposure under hypoxia-hypercapnia conditions reduced body temperature of mice to 18-19 degrees C, and maintain this state about 3-4 h after transferring into conventional gas medium. Preliminary cooling mice were administrated with TSKY that at dose 100 microg intraperitonally induced a prolonged hypothermia up to 12 h. Analogous injection without cooling raised mice temperature by 1.2 degrees C during about 2 h.

Alpha Rhythm↗
PubMed1986

Relationships between EEG and clinical characteristics in major depressive disorder.

Twenty-five patients with major depressive disorder (MDD) according to RDC were examined with computerized EEG before antidepressive treatment was initiated. Relationships between EEG parameters and clinical characteristics were studied. Age and pharmacological treatment were taken into account. Primary MDD was associated with an increase of delta amplitude. Retarded MDD was associated with an increase of delta and theta amplitudes and EEG variability. Recurrent unipolar MDD was related to a decrease of total alpha symmetry. Thus, subdiagnoses according to RDC were validated. The anxiety subsyndrome and to some extent vital symptoms, depressed mood, and CPRS total sum, were associated with asymmetry of the EEG pattern, whereas retardation was not. The number of former depressive episodes was positively correlated to amplitude of beta activity and negatively correlated to symmetry of EEG in the delta frequency band.

Adult↗