Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “EEG”

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 127 records · Page 7Linked to original sources
PubMed2004

BOLD-contrast functional MRI signal changes related to intermittent rhythmic delta activity in EEG during voluntary hyperventilation-simultaneous EEG and fMRI study.

Differences in the blood oxygen level dependent (BOLD) signal changes were studied during voluntary hyperventilation (HV) between young healthy volunteer groups, (1) with intermittent rhythmic delta activity (IRDA) (N = 4) and (2) controls (N = 4) with only diffuse arrhythmic slowing in EEG (normal response). Subjects hyperventilated (3 min) during an 8-min functional MRI in a 1.5-T scanner, with simultaneous recording of EEG (successful with N = 3 in both groups) and physiological parameters. IRDA power and average BOLD signal intensities (of selected brain regions) were calculated. Hypocapnia showed a tendency to be slightly lighter in the controls than in the IRDA group. IRDA power increased during the last minute of HV and ended 10-15 s after HV. The BOLD signal decreased in white and gray matter after the onset of HV and returned to the baseline within 2 min after HV. The BOLD signal in gray matter decreased approximately 30% more in subjects with IRDA than in controls, during the first 2 min of HV. This difference disappeared (in three subjects out of four) during IRDA in EEG. BOLD signal changes seem to depict changes, which precede IRDA. IRDA due to HV in healthy volunteers represent a model with a clearly defined EEG pattern and an observable BOLD signal change.

Adult↗
PubMed2006

EEG/(f)MRI measurements at 7 Tesla using a new EEG cap ("InkCap").

We aimed at improving the signal-to-noise ratio (SNR) of electroencephalography (EEG) during magnetic resonance imaging (MRI) by introducing a new EEG cap ("InkCap") based on conductive ink technology. The InkCap was tested with temperature measurements on an electrically conductive phantom head and during structural and functional MRI (fMRI) recordings in 11 healthy human volunteers at 7 T. Combined EEG/fMRI measurements were conducted to study the interaction between the two modalities. The EEG recordings with the InkCap demonstrated up to a five-fold average decrease in signal variance during echo-planar imaging, with respect to a cap made of standard carbon fiber leads. During concurrent EEG/fMRI measurements in human volunteers, alpha oscillations were clearly detected at 7 T. Minimal artifacts were present in the T2* and high-resolution structural MR images of the brain parenchyma. Our results show that the InkCap technology considerably improves the quality of both EEG and (f)MRI during concurrent measurements even at 7 T.

Adult↗
PubMed2002

A new technique for the analysis of background and evoked EEG activity: time and amplitude distributions of the EEG deflections.

OBJECTIVES: The EEG during background activity and that evoked in response to sensory stimuli (evoked potential, EP) has traditionally been studied by averaging and by frequency analysis. These obscure trial to trial variability. A new analysis technique is presented here which leads to single trial analysis and to insight into the mechanisms of EP generation. METHODS: This technique is based on the identification of the EEG deflections recorded on the scalp before (background) and immediately after visual stimuli. A statistical description of the time and amplitude distributions of these deflections is defined and leads to the differentiation between background and evoked activity. RESULTS: In response to stimuli, the time and amplitude of ongoing deflections (background) are re-organized (time locking) and amplified, generating the EP. Not all stimulus trials are accompanied by an appropriate response. Separate analysis of those single trials that do contain a response deflection provides information on the exact timing, variability, amplitude, etc., of those EEG deflections which contribute to the EP. CONCLUSIONS: New EEG analysis techniques are described which provide single trial EP analysis and insight into mechanisms of EP generation.

Acoustic Stimulation↗
PubMed1977

EEG operant conditioning in a monkey model: II. EEG spectral analysis.

EEG power spectral analysis was studied from 14 (alumina-gel) chronically epileptic, undrugged monkeys during an EEG operant conditioning experiment. The composite profile of the average epileptic monkey shows the majority of power to be below 10 Hz. Because of the large variance in the data, no significant changes in the EEG power spectra could be detected as a function of conditioning. The possible reasons for this large variance are discussed. Hypothesis from previous human "biofeedback" studies would allow the prediction that those frequencies corresponding to the mu and sensory-motor-rhythm should negatively covary with seizure frequency. Data from this study did not support such assertions. The method of using spectral analysis for quantifying changes in the EEG which covary with operant conditioning is evaluated.

Animals↗
PubMed1994

Long-term video-EEG monitoring revisited. The value of interictal and ictal video-EEG recording, a follow-up study.

Between October 1990 and November 1992, 100 patients were monitored at the University of Gent Epilepsy Monitoring Unit. Sixty-three patients were referred for refractory epilepsy, 38 of whom were entered in the epilepsy surgery protocol. Thirty-seven patients were evaluated for the diagnosis of attacks of uncertain origin. Average duration of monitoring was 3.5 days (2-15 days). Prolonged interictal EEG was recorded in all patients. Ictal EEG was obtained in 63 patients; the average number of recorded episodes was 3 (1-15). Pre-monitoring tentative seizure diagnosis was available in 81 patients, 59 of whom had clinical attacks. Premonitoring diagnosis was confirmed in 31 patients and revised in 28 patients. As a result of the monitoring session, anticonvulsant medication was started in 10 patients, changed in 47, stopped in 5 and left unchanged in 23 patients. Twelve patients underwent surgery. Average follow-up after monitoring was 17 months (4-30 months). Four patients were lost to follow-up; 2 patients died of an underlying disease. In the nonsurgical group (85 patients), 60 patients became seizure-free or experienced significant reduction in seizure frequency. Outcome was unrelated to the availability of ictal recording. While prolonged interictal EEG monitoring is mandatory in the successful management of patients with refractory epilepsy, ictal video-EEG monitoring is very helpful but not indispensable, except in patients enrolled for epilepsy surgery or suspected of having pseudoseizures.

Adolescent↗
PubMed2001

EEG patterns in persons exposed to ionizing radiation as a result of the Chernobyl accident: part 1: conventional EEG analysis.

Prospective conventional EEG study was carried out 3-5 and 10-13 years after the Chernobyl accident (1986) in patients who had acute radiation sickness and in emergency workers in 1986 ("liquidators"). Control groups comprised healthy volunteers; veterans of the Afghanistan war with posttraumatic stress disorder; veterans with mild traumatic brain injury; and patients with dyscirculatory encephalopathy. In 3-5 years after irradiation, there were irritated EEG changes with paroxysmal activity shifted to the left frontotemporal region (cortical-limbic overactivation) that were transformed 10-13 years after irradiation toward a low-voltage EEG pattern with excess of fast (beta) and slow (delta) activity together with depression of alpha and theta activity (organic brain damage with inhibition of the cortical-limbic system). Quantitative EEG is likely to be very informative for investigation of dose-effect relationships.

Adult↗
PubMed1983

Evaluation of ambulatory cassette EEG monitoring: III. Diagnostic accuracy compared to intensive inpatient EEG monitoring.

We assessed the ability to recognize epileptiform abnormalities on a video review of ambulatory cassette EEGs (A/EEG) by comparing two independent interpretations of an A/EEG to those derived from a routine recording and intensive monitoring by cable telemetry (C/EEG) of the same 40 patients. Both A/EEG readings concurred with the C/EEG interpretation as to normality or epileptiform abnormality in 77% of cases. Seventy-nine percent of focal and 100% of generalized interictal abnormalities, as well as all seizures, noted on C/EEG were detected by both A/EEG reviewers. Of patients with normal baseline EEGs, 37% showed epileptiform features on A/EEG versus 44% with C/EEG. Limits to the characterization of abnormalities by A/EEG and a protocol for the video review of A/EEG tapes are discussed. In those specific areas for which intensive surface EEG monitoring is most useful, ambulatory cassette EEG appears to be an acceptable intermediate-level alternative.

Adolescent↗
PubMed2002

An introduction to statistical concepts for the analysis of EEG data and the planning of pharmaco-EEG trials.

The use of descriptive statistics and graphics for electroencephalogram (EEG) data after initial data reduction and the application of hypothesis tests to EEG data are described. In planning pharmaco-EEG trials, some notion of statistical power and variability of effect size is necessary as they are used to calculate sample size in parallel-group clinical trials. The need for sensitivity analysis during the study planning phase is demonstrated as well. Because EEG data are highly dimensional data, an outline of methods for reducing dimensionality is provided. These concepts are demonstrated using data from patients with Alzheimer's disease and from healthy controls.

Alzheimer Disease↗
PubMed2004

[EEG and video-EEG explorations in refractory partial epilepsy].

The assessment of drug -resistant partial epilepsy by electrophysiological explorations (based on non-invasive EEG) involves two types of analysis: the study of the seizures, primarily by video-EEG exploration, and the study of interictal activities based on visual analysis, and in some centers on techniques of source localization (high resolution EEG and magnetoencephalography, MEG). Seizure recording can be used to confirm the focal nature and the epileptic origin of the seizure as well as other features such as severity (secondary generalization, frequency, falls etc.). In the pre-surgical approach, the video-EEG recordings enable study of the electro-clinical correlations and allow assumptions on the anatomical localization of the epileptogenic zone. Precise analysis of the localization of the interictal activities (especially within the framework of extra-temporal epilepsies) based on source localization methods, makes it possible to put forth assumptions on the localization of the irritative zone.

Anticonvulsants↗
PubMed1994

Tape-recorded EEG and the cerebral function monitor: amplitude-integrated, time-compressed EEG.

Monitoring of spontaneous brain electrical activity (EEG) has three purposes: Detecting sudden loss of background activity as an early sign of brain hypoxia/ischaemia, detection of silent seizures, and helping to diagnose brain damage. Tape-recording allows storage of upto 8 channels of standard EEG for prolonged periods, but some direct readout is necessary for monitoring purposes and review is time consuming. The Cerebral Function Monitoring technique (CFM) provides a 1/500 time-compressed recording of EEG amplitude overall EEG background activity as well as seizures. Lack of knowledge of when and how to intervene, rather than technical problems, puts a limit to the usefulness.

Brain↗
PubMed1976

[Psychophysiological studies of EEG, operational performance and the dynamics of vigilance regulation. I. The EEG during performance of Brickenkamp's attention-concentration test (test d 2) (author's transl)].

During the performance of the d 2 test developed by Brickenkamp (standardized test of attention and concentration), occipital EEG activity was registered telemetrically in 10 male students aged 25 to 32 years. Simultaneously, the pencil markings performed by the subjects, indicating the time course of their pattern recognition and discrimination, were recorded by means of a piezo-electrical transducer. The EEG behavior during test performance was evaluated by serial spectral analysis. The analysis of the EEG parameters derived from it (total power, absolute and relative alpha-power) showed that there is a relationship between these EEG measures reflecting the regulation of cortical vigilance and the error rate in the concentration test. While subjects with low error rate present a heightening of cortical arousal focused in the right occipital area, subjects with higher error rate tend to have a higher degree of general cortical activation.

Adult↗
PubMed1979

Combined dynamics of EEG and evoked potentials. I. Studies of simultaneously recorded EEG-EPograms in the auditory pathway, reticular formation, and hippocampus of the cat brain during the waking stage.

This study is carried out on single (not averaged) recordings combining the spontaneous activity preceding the stimulus onset and the EP recorded upon acoustical stimulation. These recordings, which we call EEG-EPograms, are measured simultaneously from different subdural brain structures, such as the auditory cortex, medial geniculate nucleus, inferior colliculus, reticular formation and the hippocampus of awake cats. Using a combined analysis procedure (C.A.P.), the relevant frequency components of spontaneous EEG and EPs, recorded simultaneously from these brain nuclei, are analyzed according to the consistent selectivity bands depicted by the determined amplitude-frequency characteristics. These analyses provide us the following information: (1) there is an important congruency in the time courses of simultaneous response components in common frequency bands, especially in the alpha and beta frequency ranges; (2) there exist significant coupling and synchrony between the evoked amplitude enhancements in the simultaneously recorded single response components; (3) the inter-nuclei coherency in the brain's electrical activity is enormously increased upon stimulation; (4) the evoked response magnitude can be predicted, with reasonable accuracy, from the spontaneous activity preceding the stimulation. The strong dependence of the response magnitude on the stimulus-preceding EEG is explained by means of a model network consisting of a population of relaxation oscillators, which can be brought to different states of synchrony and asynchrony. Some suggestions and comments are also made for investigators working toward theories of signal transmission in the brain.

Animals↗
PubMed1987

Video EEG telemetry using an ambulatory EEG cassette recorder.

A system of video/EEG monitoring is described which is complementary to out-patient ambulatory EEG recording and prolonged hospital admission for intensive assessment. An ambulatory EEG cassette recorder is incorporated in the system which increases the usefulness of this equipment. In addition all the recorded EEG may be rapidly reviewed. This system has proved valuable in the management of selected patients seen in a special clinic for epilepsy.

Electroencephalography↗
PubMed1994

Quantitative EEG analysis in early onset Alzheimer's disease: correlations with severity, clinical characteristics, visual EEG and CCT.

We report EEG findings in 15 presenile Alzheimer patients (probable Alzheimer's disease according to NINCDS-ADRDA criteria) in relation to clinical characteristics. The quantitative EEG was analysed in terms of absolute band power while accounting for EOG and EMG artifacts, respectively. The degree of dementia is strongly reflected by an increase of power in the delta frequency band, accentuated on the left hemisphere, as well as decrease of alpha activity. Longer duration of disease is associated with a decrease of power in the alpha frequency band, earlier age at onset with an additional increase of power in the theta frequency band. Visual EEG evaluation correlates highly with the degree of dementia, in contrast to visually assessed CCT.

Age of Onset↗
PubMed1996

Use of non-linear EEG measures to characterize EEG changes during mental activity.

Non-linear EEG analysis provides a possibility for studying the dynamical changes in cortical networks related to mental activity. In this study the correlation dimension D2 was used to study local changes in complexity, and the mutual dimension Dm was used to assess changes in the dynamical coupling between different brain areas. EEGs were recorded in 25 healthy subjects under three conditions: (1) eyes closed, (2) eyes open, and (3) mental arithmetic with eyes closed (serial subtraction of 7s from 1000). In the eyes-closed condition, D2 was lower at parieto-occipital sites. D2 increased during the eye-open and arithmetic conditions. Contrary to the D2, the Dm showed no regional differences in the eyes closed condition. A clear increase in Dm was seen during eyes open and arithmetic. We conclude that both the correlation dimension and the mutual dimension are very sensitive to EEG changes during simple visual information processing and during mental arithmetic. However, these measures seem to be relatively non-specific, and correlate only weakly with performance on the arithmetic task.

Adult↗
PubMed1994

Interactive effects of MK-801 and morphine on EEG, EEG power spectra and behavior in rats: I. Morphine tolerance development.

This study investigated a potential interaction between MK-801 and morphine tolerance using electroencephalography (EEG), EEG spectral parameters and behavior in the rat. Rats were treated for 7 days with morphine alone or with morphine and MK-801. Control groups received chronic MK-801 alone or saline. On day 8 all rats received morphine alone. Co-treatment significantly accelerated the development of tolerance to morphine-induced total power and latency to sleep onset. Co-treatment, but not morphine alone, produced tolerance to morphine-induced complexity and edge frequency, and produced tolerance equal to that from morphine alone in duration of EEG bursting. MK-801 co-treatment decreased, where chronic morphine alone increased, the excitatory response to morphine. Our results support recent reports that chronic morphine treatment produces supersensitivity to glutamate in the rat cortex and alteration in mesolimbic dopamine levels that are modulated by glutamatergic activity.

Animals↗
PubMed1992

Effects of chronic morphine administration and naloxone on EEG, EEG power spectra, and associated behavior in two inbred rat strains.

Utilizing behavioral and electroencephalographic (EEG) assessments, two inbred rat strains, Lewis (LEW) and Fischer 344 (F344), were exposed to morphine (IV) over a period of 7 days to discern differences in tolerance development. Following morphine injection, the LEW group demonstrated a greater mean total amount, as well as a greater rate of reduction, of stuporous behavior across the 7 days tested. Differences in patterns of latency to onset of slow-wave sleep between the two strains were also exposed. EEG analysis of spectral parameters utilizing an analysis of variance with repeated measures revealed that peak frequency, mean frequency, and edge frequency differed as a function of inbred rat strain. All spectral parameters differed as a function of duration of morphine injection; linear trends were indicated for both strains. Naloxone was administered (IV) following the 7 days of morphine to delineate dependence differences. LEW animals reflected a greater amount of behavioral responses, for example, wet-dog shakes, diarrhea, body stretch, and sluggish behavior. However, F344 rats demonstrated a greater alteration in two spectral parameters assessed: peak frequency and total power. Genetic variability appears to play a major role in both morphine tolerance and dependence as indicated by differences in EEG and behavioral responses.

Animals↗