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PubMed1998

Using electroencephalography to study functional coupling between cortical activity and electromyograms during voluntary contractions in humans.

Previous studies of neuronal oscillations in sensorimotor cortex in humans and primates have observed rhythmic 15-30 Hz activity, which is correlated with motor output. In humans, this work has been limited to magnetic recordings. In the present study we investigate if similar results can be obtained using electroencephalography (EEG). EEG recordings were made from over the sensorimotor cortex of five adult subjects who performed repeated periods of maintained wrist extension and flexion. Coherence analysis between EEG and electromyogram (EMG) recordings from these muscles revealed correlation in the 15-30 Hz range, with a synchronous correlation structure which matches that previously observed in humans and in paired cortical recordings from primates. We conclude that EEG is equally efficient at investigating functional aspects of these cortical rhythms during voluntary movement in humans.

Adult↗
PubMed1998

Face-selective processing in human extrastriate cortex around 120 ms after stimulus onset revealed by magneto- and electroencephalography.

Quick recognition of faces is crucial to a variety of human interactions, and highly specialized pathways may be involved in the processing of faces. To reveal selectivity to faces in early cortical processing, whole-scalp magnetoencephalography (MEG) and electroencephalography (EEG) were used to record event-related responses to faces and degraded faces and their inverted counterparts. We observed increases in the peak latency and amplitude of the early 120-ms component (P120) for the inverted faces. These effects were enhanced for the 1 70-ms component (N170). For the degraded counterparts, a significant effect of the inversion was observed only for the N170, which was strongly delayed. Source modelling suggested that the early response originated at the posterior occipital areas whereas the later response was generated anterior and lateral to this location. We conclude that under sufficiently good conditions face-selective activity may be taking place during the P120.

Brain Mapping↗
PubMed1999

Prediction of neurological outcome after birth asphyxia from early continuous two-channel electroencephalography.

OBJECTIVE: To determine whether two-channel continuous electroencephalography (EEG) applied within 12 h of birth can predict the severity of neurological complications and neurodevelopmental outcome following birth asphyxia. METHODS: A continuous two-channel EEG was performed within 12 h of birth in 22 infants suspected of having suffered birth asphyxia and 11 healthy control infants (22 infants at a general and 11 at a specialist paediatric unit). Criteria to categorise normal and abnormal EEG records were defined and compared with the severity of hypoxic/ischaemic encephalopathy (HIE) and with neurodevelopmental outcome, assessed at or after 12 months of age. RESULTS: EEG recordings were commenced at a median (range) of 2 h 50 min (1 h 45 min to 12 h) after birth. Technically satisfactory recordings were obtained in all but one infant. All control infants remained asymptomatic and had a normal EEG with discernible sleep/awake periods. 12 h after birth the EEG was normal in all 12 infants suspected of asphyxia who remained well or developed grade 1 HIE and was abnormal in six of nine infants with grade II or III HIE. Fifteen of 16 infants suspected of asphyxia with a normal neurodevelopmental outcome had a normal EEG at 12 h; transient abnormalities lasting not more than 8 h had been detected in three of these infants. All five infants who died or developed neurodevelopmental abnormalities had an abnormal EEG. At 12 h of age the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and likelihood ratio for predicting severe (grade II or III) HIE were: 67, 100, 100, 80% and infinity and for subsequent death or neurodevelopmental impairments: 100, 94, 83, 100 and 16%, respectively. Assessment of the EEG before 12 h of age altered prognostic accuracy: 4 h after birth the sensitivity, specificity, positive and negative predictive values and the likelihood ratio for poor neurodevelopmental outcome were 100, 71, 33%, 100 and 3.7%, respectively (16 infants). CONCLUSION: Continuous two-channel EEG is an accurate tool for assessing the severity of neurological insult soon after birth asphyxia.

Asphyxia Neonatorum↗
PubMed2002

Combination of neonatal electroencephalography and ultrasonography: sensitive means of early diagnosis of periventricular leukomalacia.

This study was performed to assess the predictive value of ultrasonography and electroencephalography (EEG) in order to identify infants with periventricular leukomalacia (PVL) during the early neonatal period, especially non-cystic cases, and to clarify the combination of ultrasonographic and EEG findings that are the most useful. We studied 288 eligible infants, whose gestational ages ranged between 27 and 32 weeks. PVL was observed in 49 infants (26 cystic PVL and 23 non-cystic PVL). On ultrasonography, 31 infants with PVL were detected on the basis of definite periventricular echodensity (PVE). Thirty-seven infants had at least one of equivocal or definite PVE or cystic changes, but the other 12 did not have any of them. The sensitivity and specificity were 0.76 and 0.81, respectively. In EEG findings, acute stage abnormalities (ASA) of grade II or more were recognized in 31 infants with PVL. The sensitivity and specificity were 0.63 and 0.91, respectively. Equivocal or definite chronic stage abnormalities (CSA) were seen in 43 infants, the sensitivity and specificity being 0.88 and 0.84. The sensitivity of CSA was higher than that of ASA, and the specificity of ASA was higher than that of CSA. When these EEG findings were combined, 45 infants with PVL were detected. The sensitivity, specificity, positive predictive value, and negative predictive value were 0.92, 0.77, 0.45, and 0.98, respectively. Moreover, ultrasonographic and EEG findings were combined, 46 out of the 49 infants with PVL were detected with a sensitivity of 0.94 and a specificity of 0.64. The results indicated that EEG may be suitable for detecting infants at risk for development of PVL on the basis of its high sensitivity, and ultrasonography may be useful for confirming the presence of PVL on the grounds of its high specificity. Appropriate use of these measurements will make an early diagnosis of infants with PVL possible, even in non-cystic cases.

Electroencephalography↗
PubMed2001

Predicting relapse to alcohol and drug abuse via quantitative electroencephalography.

A sensitive and specific screening test that would identify the subset of substance-abusing patients at highest risk for relapse would constitute an important advance for treatment planning. This study examined the relative value of quantitative electroencephalography as a rapid, inexpensive, and noninvasive measure of relapse potential. The subjects were 107 substance-dependent patients enrolled in residential treatment programs. All were unmedicated and free of the complicating effects of major medical and neurological disorders. Structured clinical interview data and a 5-minute recording of the resting, eyes-closed electroencephalogram were obtained after patients had verifiably maintained abstinence for 1-5 months. Patients were then monitored for relapse or successful abstinence by research staff for an ensuing 6-month period. ANCOVAs of EEG power spectral density within pre-defined frequency bands revealed an enhanced amount of high frequency (19.5-39.8 Hz) beta activity among the 48 patients who later relapsed compared to both 59 patients who maintained abstinence and 22 additional subjects with no history of substance dependence. Importantly, in subsequent logistic regression analyses, fast beta power was found to be superior to severity of illness, depression level, and childhood conduct problems in predicting relapse. With fast beta power as the sole predictor, the sensitivity, specificity, and positive and negative predictive value parameters for discriminating outcomes were 0.61, 0.85, 0.75, and 0.74, respectively. Additional ANCOVAs revealed that the EEG difference between relapse-prone and abstinence-prone groups was related to the interaction of two premorbid factors, viz., childhood Conduct Disorder and paternal alcoholism. The enhancement of fast beta electroencephalographic activity in patients who will later relapse most likely originates from a premorbid and subtle dysfunction involving frontal brain regions.

Adult↗
PubMed2003

Nonlinear dynamic characteristics of electroencephalography in a high-dose pilocarpine-induced status epilepticus model.

We applied nonlinear analysis to the results of electroencephalography (EEG) in a pilocarpine-induced status epilepticus (SE) model to characterize nonlinear dynamics according to SE phase. Nine male Sprague-Dawley rats weighing 150-250 g were used. EEG was classified into four phases in addition to baseline EEG (phase 0) as follows: phase 1, discrete seizures; phase 2, continuous ictal discharges; phase 3, early periodic epileptiform discharges (PEDs); and phase 4, late PEDs. High-dose diazepam was administered at phase 4 to terminate SE. Diazepam controlled SE in five rats (group 1), while it failed to stop SE in the rest (group 2). The presence of nonlinearity was determined by time reversal asymmetry statistics using a surrogate data set. The correlation dimension (D(2)) was calculated to characterize the dimensional complexity of each phase of SE. EEG of later phases of SE showed strong nonlinearity, whereas no or only weak nonlinearity was noted at phases 0 and 1. D(2) showed the highest value at phase 0 and decreased progressively. Considering therapeutic responsiveness, D(2) showed significant differences between the two groups at phases 2 and 4. These results suggest that nonlinear dynamic changes in the later SE phases reflect underlying pathophysiological changes that contribute to determining therapeutic responsiveness in the pilocarpine-induced SE model.

Animals↗
PubMed1999

A computer-based information system for epilepsy and electroencephalography.

This paper describes a standardised computer-based information system for electroencephalography (EEG) focusing on epilepsy. The system was developed using a prototyping approach. It is based on international recommendations for EEG examination, interpretation and terminology, international guidelines for epidemiological studies on epilepsy and classification of epileptic seizures and syndromes and international classification of diseases. It is divided into: (1) clinical information and epilepsy relevant data; and (2) EEG data, which is hierarchically structured including description and interpretation of EEG. Data is coded but is supplemented with unrestricted text. The resulting patient database can be integrated with other clinical databases and with the patient record system and may facilitate clinical and epidemiological research and development of standards and guidelines for EEG description and interpretation. The system is currently used for teleconsultation between Gentofte and Lisbon.

Electroencephalography↗
PubMed2003

A review of electrophysiology in attention-deficit/hyperactivity disorder: I. Qualitative and quantitative electroencephalography.

OBJECTIVE: This article reviews the electroencephalography (EEG) literature in relation to attention-deficit/hyperactivity disorder (AD/HD). METHODS: The review briefly outlines the history of the disorder, focusing on the changing diagnostic systems which both reflect and constrain research into AD/HD. Both qualitative and quantitative EEG studies are examined, and their results are discussed in relation to various models of AD/HD. Implications of these data for future research and development in AD/HD are considered. RESULTS: In terms of resting EEG, elevated relative theta power, and reduced relative alpha and beta, together with elevated theta/alpha and theta/beta ratios, are most reliably associated with AD/HD. Theta/alpha and theta/beta ratios also discriminate diagnostic subgroups of AD/HD. Recent studies of EEG heterogeneity in this disorder indicate the existence of different profiles of cortical anomalies which may cut across diagnostic types. CONCLUSIONS: The research to date has identified a substantial number of EEG correlates of AD/HD which hold promise for improving our understanding of the brain dysfunction(s) underlying the disorder. Further work in this field may benefit from a broader conceptual approach, integrating EEG and other measures of brain function.

Attention Deficit Disorder with Hyperactivity↗
PubMed1999

Modern electroencephalography: its role in epilepsy management.

Epilepsy is the area in which electroencephalography is probably of greatest potential clinical value, and yet is most abused. In general, the sensitivity of the waking interictal EEG for detecting epilepsy and its specificity for distinguishing epilepsy from other episodic disorders are both very limited, and routine examination for diagnostic screening or follow up is of little value. However, as this review attempts to demonstrate, EEG is of crucial importance for answering specific, clearly defined questions which commonly arise in the management of seizure disorders, especially so, when non-routine and if necessary complex investigations are undertaken, to address the problems of individual patients.

Diagnosis, Differential↗
PubMed1997

Electroencephalography as a diagnostic instrument in Alzheimer's disease: reviews and perspectives.

Electroencephalography is the only diagnostic instrument directly reflecting cortical neuronal functioning, and it remains an important clinical tool in the diagnosis and differential diagnosis of Alzheimer's disease (AD). Although a normal EEG is found in many patients with mild AD, a pathological EEG is an important finding, because such a result is not in line with differential diagnoses such as depression or pseudodementia within a dissociative disorder. The vast majority of patients with moderate to severe AD have a pathological EEG. A normal EEG in this patient group is more in line with subcortical dementia or frontal lobe degeneration than with AD. Compared to SPECT or routine structural brain imaging (cCT, MRT), EEG has a comparable diagnosis sensitivity and a higher specificity. For monitoring changes of brain function by serial recordings (e.g., during therapy with antidementia drugs), EEG is the best available method.

Aged↗
PubMedDate not supplied

When combined, early bedside head ultrasound and electroencephalography predict abnormal computerized tomography or magnetic resonance brain images obtained after extracorporeal membrane oxygenation treatment.

Definitive neuroimaging of the brain using computerized tomography (CT) or magnetic resonance imaging (MRI) in extracorporeal membrane oxygenation (ECMO)-treated infants must be delayed until after this therapy is completed. Bedside head ultrasound (HUS) and electroencephalography (EEG) studies during ECMO, if highly correlated with later definitive neuroimaging, might be used to affect the acute clinical care and early parental counseling of infants with severe cardiorespiratory failure. One hundred and sixty ECMO-treated patients had both bedside EEG and HUS studies performed during ECMO, as well as a later CT or MRI study prior to hospital discharge. There was a significant difference in CT or MRI findings among patients having normal studies on both the HUS and EEG, compared to those having an abnormality on either the HUS or the EEG, and compared to those having abnormalities on both studies. In ECMO-treated infants, the combination of a normal bedside HUS and an EEG without marked abnormalities is highly predictive of normal post-ECMO CT and MRI neuroimaging studies.

Brain↗
PubMed2001

Quantitative electroencephalography spectral analysis and topographic mapping in a rat model of middle cerebral artery occlusion.

Electroencephalography (EEG) has a long history in clinical evaluations of cerebrovascular disease. Distinct EEG abnormalities, such as increased slow delta activity, voltage depression and epileptiform discharge, have been identified in stroke patients. However, preclinical use of EEG analysis of cerebral ischaemia is less documented. We report a new rat model of EEG topographic mapping during permanent and transient middle cerebral artery occlusion. Ten EEG electrodes were implanted on the rat skull, symmetrically covering the cortical regions of two hemispheres. Monopolar EEG recordings were acquired from each animal at multiple time points during the initial 24 h, and again once daily for 7 days. Traditional EEG examinations, quantitative EEG (qEEG) spectral analysis and topographic EEG mapping were employed for comprehensive data analyses. Several distinct spatiotemporal EEG abnormalities were identified in the ischaemic rat brain. In the ipsilateral hemisphere, pronounced increase in delta activity was observed in each recorded area within 24 h of injury. While sharp waves and spike complexes dominated the parietal region, a nearly isoelectric EEG state was seen in the temporal region. After 48 h, spontaneous, albeit incomplete, recovery of EEG activities developed in all rats. Reperfusion appeared to promote delta and alpha recovery more efficiently. The contralateral EEG changes were also recorded in two phases: an acute moderate increase in delta activities with intermittent rhythmic activities, followed by a delayed and significant increase in beta activities across the hemisphere. The similarities of rat qEEG profiles identified in this study to that of stroke patients and the application of topographic mapping broaden our research technology for preclinical experimental studies of brain injury.

Animals↗
PubMed2001

Effect of medetomidine on electroencephalography and use of a quantitative electroencephalograph for evaluating sedation levels in dogs.

This study was designed to characterize the effect of medetomidine (Med) on canine electroencephalography (EEG), to evaluate the use of quantitative EEG for assessing sedation levels and to explore the correlation between the serum concentration of Med and the quantitative EEG. Four groups of dogs were given Med at doses of 20, 40, 80 and 160 microg/kg (Med-20, Med-40, Med-80 and Med-160 groups). Following Med administration, there was synchrony between each unipolar EEG lead. On EEG power spectrum analysis of the bipolar leads, all groups showed a significant depression of the 14-30 Hz components. The power of the 1-3 Hz component in the Med-80 and Med-160 groups was significantly increased, although there were few changes in the other groups. Similar results were obtained from raw data analysis. As a result of quantitative EEG analysis, spectrum edge frequency 90 analysis (SEP90) showed that the frequency was significantly reduced in all groups after Med administration. A dose-response effect was observed in all groups except for the Med-160 group. Both of these EEG analyses were significantly correlated with the serum concentration of Med. However, the result of the SPF90 analysis sugested a stronger correlation than that for median edge frequency analysis. In conclusion, care must be taken in veterinary clinical diagnoses when Med is used during EEG recording, as Med may cause increased activity in the low frequency band and a decrease in high frequency band activity. In addition, quantitative EEG analysis may be useful in assessing the depth of sedation and in further studies on Med administration.

Anesthesia↗
PubMed1999

Observation and execution of movement: similarities demonstrated by quantified electroencephalography.

Quantified electroencephalography (qEEG) was used to compare cerebral electrical variations while human subjects (10 males and 10 females) were observing and executing finger movements and while they were resting. Video recording enabled elimination of subjects performing involuntary movements. EEGs were recorded from 14 sites in seven frequency bands: theta 1, theta 2, alpha 1, alpha, beta 1, beta 2 and beta 3. Analyses were performed on logarithmically transformed absolute spectral power values. Both observation and execution of finger movements involved a decrease in spectral power compared with resting. This decrease was significant only for the alpha 1 frequency band (7.5-10.5 Hz) and it involved nine of the 14 electrode locations (F7, F8, F4, T6, T5, C3, C4, P3 and P4). This indicates that the motor cortex and the frontal cortex are specifically activated by both observation and execution of finger movements. These results provide evidence that observation and execution of movement share the same cortical network.

Adult↗
PubMed2003

Anticipatory cortical responses during the expectancy of a predictable painful stimulation. A high-resolution electroencephalography study.

In the present study, high-resolution electroencephalography techniques modelled the spatiotemporal pattern of human anticipatory cortical responses preceding expected galvanic painful stimuli (non-painful stimuli as a control). Do these responses reflect the activation of associative other than somatosensory systems? Anticipatory processes were probed by alpha oscillations (6-12 Hz) for the evaluation of thalamocortical channels and by negative event-related potentials for the evaluation of cortical excitability. Compared with the control condition, a progressive reduction of the alpha power was recognized over the primary somatosensory cortex from 2 s before the painful stimulation. In contrast, the anticipatory event-related potentials were negligible during the expectancy period. The results on the alpha power suggest that the expectancy of the painful stimulation specifically facilitated the somatosensory thalamocortical channel. Remarkably, the associative frontal-parietal areas were not involved, possibly due to the predictable and repetitive features of the painful stimulus. The present results also suggest that negative event-related potentials are modest preceding warned stimuli (even if painful) with a simple information content.

Adult↗
PubMed1998

Changes in the structure of sleep spindles and delta waves on electroencephalography in patients with nocturnal enuresis.

OBJECTIVE: To evaluate the mechanism of the dysfunction of arousal in patients with Type I and Type IIa enuresis. PATIENTS AND METHODS: The numbers of sleep spindles and delta waves were analysed during electroencephalography in 19 patients with enuresis (17 male, two female, mean age 9.7 years, range 8-14). RESULTS: In four patients with Type I enuresis, who awoke spontaneously and remained dry as a result of urinary sensation, the numbers of sleep spindles and delta waves diminished gradually and finally disappeared just before the patients awoke completely. In the remaining nine patients with Type I enuresis, there was no decrease in the number of sleep spindles and delta waves, and enuresis occurred without the subjects awakening. In the six patients with Type IIa enuresis, there was no arousal reaction or generation of sleep spindles on urination while asleep. CONCLUSIONS: An immaturity in the function of the thalamus might be a cause of the arousal dysfunction in patients with Type I enuresis. In Type IIa enuresis, a possible abnormal or immature arousal mechanism in the pons or the lower tract may be responsible.

Adolescent↗
PubMed2002

Effects of nicardipine and clonidine on cognitive functions and electroencephalography in hypertensive patients.

The aim of this study was to investigate the cognitive and electroencephalography (EEG) short-term effects of a calcium antagonist, nicardipine, compared to placebo and clonidine (which, having known sedative effects, acted as a negative control) for 15 days in elderly hypertensive patients with memory complaints. Nicardipine and clonidine were compared with placebo in a double-blind, randomized, three-way cross-over controlled study after a 2-week placebo run-in period. This was a phase II clinical study carried out on out-patients in a single research centre. Fifteen elderly (63 +/- 10 years) hypertensive patients, without dementia but with memory complaints, were included. Psychomotor performance and cognition were assessed using both an extensive battery of validated psychometric tests (which evaluated attention and vigilance, body sway and memory) and an EEG profile. Cardiovascular parameters measured were blood pressure and heart rate. No detrimental effects of nicardipine were found on attention, vigilance, body sway or memory. Nicardipine produced a significant increase in alpha EEG energies, which may indicate possible alerting effects. In contrast, clonidine induced well-known deleterious sedative effects in psychometric tests and in EEG analysis (decrease in alpha and increase in delta and theta waves). The two drugs produced equivalent decreases in blood pressure at steady state. In conclusion, clonidine induced well-known sedative effects, while nicardipine did not impair central nervous system activity and may have had some short-term alerting effects in elderly hypertensive patients with memory complaints. This study supports the hypothesis of a dissociation between blood pressure and direct drug effects on the central nervous system.

Aged↗
PubMed2002

Epilepsia partialis continua--a clinical and electroencephalography study.

Epilepsia partialis continua (EPC) is a rare type of localization-related motor epilepsy. Clinical spectrum, electroencephalography (EEG) characteristics and various prognostic factors in EPC were studied in 20 patients. Patients who fulfilled the criteria for EPC between the years 1985 and 1999 were included in this retrospective and prospective study. The mean age was 18 years (range 5 months-70 years). Eleven patients (55%) had Type 1 EPC and in the remaining nine (45%) patients there were features of Type 2 EPC. Among children Rasmussen's encephalitis and viral encephalitis were the commonest cause for EPC. Encephalitis and vascular aetiology were frequently observed in adults. Tuberculous meningitis and tuberculomas occurred evenly in both the groups. The cause was unknown in two cases. Focal EEG abnormalities commonly consisted of discrete spikes, sharp waves (or) slow wave activity and periodic lateralized epileptiform discharges. The mean duration of follow up was 9.6 months with a range between 1 month and 4 years. Cognitive decline, motor deficits and pharmacoresistance to drugs were significantly seen among children with Type 2 EPC. Patients with Type 1 EPC had mild impairment of functional status with good response to treatment. The long-term prognosis depends upon the underlying cause.

Aged↗