Increased Delta Activity Research Articles

Encephalopathy from acute liver failure and from acute hyperammonemia in the rabbit. A clinical and biochemical study

To study the molecular basis of ammonia toxicity, highly reproducible models of acute liver failure and acute hyperammonemia in the rabbit were developed. Acute liver failure was induced by two-stage liver devascularization, and acute hyperammonemia by prolonged ammonia infusion such that the plasma ammonia pattern found in acute liver failure was simulated. Clinical symptoms, spectral analysis of the EEG, biochemistry (blood gases, renal function, electrolytes and markers of hepatic injury) and the presence of cerebral edema were studied. During acute liver failure severe encephalopathy developed after 10.2 +/- 1.9 h (n = 6, mean +/- SEM). Other liver-failure-associated abnormalities were cerebral edema, lactic acidosis, renal dysfunction, hypothermia and septicemia. During acute hyperammonemia, severe encephalopathy developed after 18.2 +/- 0.4 h (n = 6, mean +/- SEM). Other abnormalities found were cerebral edema and lactic acidosis. In both animal models comparable EEG changes were observed (a decrease in mean dominant frequency and theta-activity, and an increase in delta activity). However, these changes were not statistically significant, and non-specific as they also occurred in control rabbits despite their clinical wellbeing. This study demonstrates in the rabbit the similarity between encephalopathy due to acute ischemic liver failure and that due to hyperammonemia. An observed difference in hyperammonemia-induced encephalopathy was pronounced ataxia, which did not occur during acute liver failure, whereas hypothermia, sepsis and renal failure occurred exclusively in acute liver failure. Our models appear satisfactory for the study of hepatic encephalopathy and ammonia toxicity.

Computerized EEG Topography in Childhood Migraine Between and During Attacks

Topographic EEG mapping was performed in 58 migrainous children (mean age: 12.9 years; 39 without, 19 with aura) between attacks. Ten children were also recorded during an attack with visual aura. Between attacks there were no significant differences between migraineurs and age-matched controls. During visual aura a decrease in occipital alpha power contralateral to the affected hemifield was found in all patients. This was followed by a bilateral frontal increase in delta power, and, during the headache, by an increased delta activity in posterior-temporal and occipital electrode sites. The possible brain mechanisms underlying these EEG changes are discussed.

Aging and spectral analysis of EEG in normal subjects: a link to memory and CSF AChE.

We studied the effect of aging on EEG spectra recorded from T5-O1 (T6-O2) derivation. The aging series composed of 52 normal individuals aged 20 to 91 years. Seventy-nine per cent of visual and 81% of quantitative EEGs were considered normal. The absolute amplitude of delta and theta bands and absolute power of delta band were lower for the oldest group (aged 60 and over) than for the youngest group (aged 20-39 years). Age was inversely related to the amount of delta and theta indicating that the amount of slow activity in quantitative EEG does not increase with age in the context of good health status. Women had more beta activity compared with men. In addition, the amount of beta and alpha bands showed tendency for a reduction with age. Fifteen subjects aged 50 years or older participated in a 2-year follow-up including EEG and neuropsychological evaluation. Seven of them deteriorated in learning ability and showed increase in delta activity. In the oldest age group, delta amplitude was positively correlated with intrusion errors in the list learning test and inversely related to acetylcholinesterase activity of the CSF. Thus, a link between the cholinergic system, EEG slowing and memory problems in old age is suggested.

Slowing of EEG in Parkinson's disease

EEG studies of Parkinson's disease (PD) have shown that the incidence of EEG abnormalities is higher than in normal old individuals. The most common alteration in PD is generalized slowing of the EEG. We studied 18 patients with parkinson dementia, 18 age-matched Parkinson patients without dementia and 20 controls. The absolute and relative amplitudes of delta, theta, alpha and beta bands and the peak and mean frequency were calculated from EEG spectra recorded from the T6-O2 derivation. All variables differed significantly in Parkinson dementia patients compared to controls. The most conspicuous finding was the increase of delta activity. Parkinsonian patients without dementia had more theta activity and the frequencies were slow compared to controls. We conclude that parkinsonian subgroups have distinct patterns of abnormality in EEG spectra: Parkinson patients with dementia have distinctly slower EEGs than in patients without dementia.

Effect of alpha 2 antagonists and an agonist on EEG slowing induced by scopolamine and lesion of the nucleus basalis

In the present study, the effects of an alpha 2 agonist (clonidine, 1.0 mg/kg, i.p.) and two antagonists (atipamezole, 1 and 10 mg/kg s.c. and yohimbine, 3.0 mg/kg i.p.) were studied on the EEG activity of naive rats, pretreated with either saline or scopolamine (0.8 mg/kg), or rats receiving lesioning of the nucleus basalis. The alpha 2 antagonists increased fast activity (alpha and beta). Clonidine increased slow wave activity (increased in spectral amplitudes) during periods of immobility and mobility. The EEG slowing, induced by scopolamine, was not alleviated by atipamezole or yohimbine, but in immobile rats, an increase in the delta and theta amplitudes was augmented by clonidine. In nucleus basalis-lesioned rats, the increase in delta activity was partially normalised by the alpha 2 antagonists. The decrease in the beta amplitude, induced by lesioning of the nucleus basalis, was not alleviated with either atipamezole or yohimbine. Clonidine increased the slow wave activity in nucleus basalis-lesioned rats and induced an increase in delta and theta bands during immobility. No changes were induced by clonidine in the EEG recorded from rats with lesions of the nucleus basalis.

Clinical Recovery and Sleep Architecture Degradation

We achieved a unique and timely recording of cerebral activity in a 70 year old woman immediately pre- and post-stroke, while studying the effect of acute cerebral infarction on sleep-electroencephalogram (EEG) patterns. Normal patterns, except for increased wakefulness, were recorded during two pre-infarct polysomnograms. Immediately following cerebral infarction increased delta activity was recorded from the infarcted hemisphere only. Initially, REM sleep could not be recorded from either side; however, on the third post infarct day REM sleep returned. Background EEG levels from both hemispheres became progressively slower, flatter and simpler. In addition, sleep spindles and the distinctive saw-tooth wave forms of sleep almost disappeared. At one year post-stroke sleep-EEG rhythm recordings from both hemispheres became more similar except for persisting delta activity from the left hemisphere. Unexpected deterioration of sleep-EEG pattern recordings from the undamaged hemisphere taken during the patient's clinical recovery remains unexplained. Serial sleep recording may facilitate the study of brain recovery, activity and reorganization following stroke.

Abnormal EEG Responses to Photic Stimulation in Schizophrenic Patients

Numerous studies have differentiated schizophrenic patients and normal controls in electroencephalography (EEG) spectral patterns recorded at rest. We replicated the resting EEG spectral differences between these groups and observed significant differences in periodic photic stimuli on the EEG spectra. Drug-free schizophrenic male patients (n = 8, mean age = 23.9) and normal male controls (n = 11, mean age = 24.3) were studied. Eighty seconds of EEG were collected from each subject for each of four experimental conditions: one resting and three photic-driving conditions (2.38, 4.54, and 8.33 Hz). Eye movement and other movement artifacts were minimized by use of an automatic amplitude threshold filter. Although large eye movements could be excluded as confounding factors, the filter could not for certain exclude small eye movements. Subjects were instructed to keep their eyes closed throughout. A significant difference was found between the groups both at rest and following photic stimulation in EEG activity. This result was characterized by increased delta activity and decreased alpha activity in schizophrenic patients at rest. The EEG activity following the photic driving also differentiated the groups. Schizophrenic patients had decreased sensitivity to the photic stimulation in the alpha range for spectra derived from both fundamental and harmonic analysis.

Effect of attention on frontal distribution of delta activity and cerebral metabolic rate in schizophrenia

15 patients with schizophrenia and nine normal volunteers had 32 channel topographic EEG recorded for spectral analysis during the uptake of 18-F-deoxyglucose (FDG) for position emission tomography (PET). Both patients and controls performed the Continuous Performance Test, a visual vigilance task, during FDG uptake. EEG was also obtained during an initial pre-FDG resting period. Each EEG epoch was individually inspected for eye movement artifacts. Analysis confirmed increased delta activity in the frontal region of patients with schizophrenia in comparison to normal controls, and a significant correlation between increased frontal delta and relative reduction in frontal lobe metabolism among patients with schizophrenia. This finding of increased delta is consistent with PET, blood flow and topographic EEG studies of schizophrenia, suggesting reduced frontal activity.

Computerized EEG in schizophrenia.

Despite advances in the processing and display of electroencephalographic (EEG) data, the utility of this inexpensive and noninvasive technique in the investigation of schizophrenia has not been well established. We studied the resting EEG in 19 medication-free patients with chronic schizophrenia and 21 normal controls. Patients with schizophrenia had increased delta activity which was not specific to the frontal regions. Schizophrenic patients also had increased fast activity, and this increase was left sided for the fast beta frequency. Alpha frequency was reduced (less than 10.2 Hz) in 7 of 16 schizophrenic patients. Moreover, those patients with an alpha frequency reduction had a significantly larger mean cerebral ventricular size. These results indicate that the EEG does detect neurophysiological changes in schizophrenia. Our understanding of these changes may be enhanced by other neuroimaging techniques such as computed tomography.

Computed electroencephalographic activity mapping in schizophrenia. The resting state reconsidered.

Several topographic mapping studies of electroencephalographic (EEG) power spectra have reported increased slow (delta) activity in the frontal regions of schizophrenic patients. Using supraorbital and lateral canthus electrodes to detect eye movement, we deleted EEG epochs during eye movement in 15 medication-free patients with schizophrenia and in 13 normal control subjects. Power spectral analysis of the 28-channel EEG demonstrated a diffuse mild increase in delta activity in schizophrenic patients compared with normal control subjects but no tendency for frontal localization of this slow activity. There were no differences between schizophrenic patients and normal control subjects in other frequency bands. These results, which replicate earlier findings of increased delta activity in schizophrenia, emphasize the importance of excluding the slow activity due to eye movement in the comparisons of summed EEG spectra. This emphasis can best be ensured by equating the summed spectra from extraocular movement channels of experimental and control groups.

The effect of sodium valproate on sleep, reaction times, and visual evoked potential in normal subjects.

The effect of enteric-coated sodium valproate on 10 normal volunteer subjects was evaluated using simple reaction times, the visual evoked potential (VEP), and EEG sleep recording. Placebo, low-drug (500 mg), high-drug (1,000 mg), and withdrawal conditions were investigated. No significant treatment effect was found for simple reaction time nor was there any significant effect on either the latency or the amplitude of the VEP. Sleep recordings were analysed visually and also using an automated technique consisting of simple period analysis. The automated sleep results suggested that there was a decrease in rapid eye movement activity and an increase in delta activity under the high-drug condition. The visually analysed data did not reach significance, although they followed the same trends as those analysed automatically. It is possible that the automated results reflect an EEG frequency change rather than a change in the sleep cycle itself caused by treatment with sodium valproate.

Thiopental bolus during carotid endarterectomy-rational drug therapy?

Ten studies were performed to examine the time course of arterial and venous thiopental concentrations following the administration of thiopental (4 mg X kg-1 over 3 min) for cerebral protection during carotid occlusion in nine patients undergoing elective carotid endarterectomy; in five patients the time course of EEG change was also studied. The arterial and venous thiopental concentrations were similar with no evidence of a sustained arterial-venous gradient. The average arterial concentration was 20.1 microgram X ml-1 +/- 10 (SD) at 2 min after thiopental, and fell rapidly to 13.0 micrograms X ml-1 +/- 3.2 at 5 min, 10.7 micrograms X ml-1 +/- 4.4 at 10 min and 6.2 micrograms X ml-1 at 30 min. After thiopental the EEG record showed an increase in delta activity and in four patients a burst suppression pattern was seen. The duration of burst suppression activity was variable (130 to 367 seconds) but in all instances cortical activity had returned to the pre-thiopental level by five to ten minutes. Thus concentrations of thiopental of 10-30 micrograms X ml-1 were associated with EEG burst suppression and both were seen only within the first five minutes after drug administration. In contrast the carotid artery was occluded for considerably longer (26 +/- 4) minutes. We conclude that, since there was no sustained arterial-venous gradient, either arterial or venous concentrations are adequate for the study of thiopental pharmacokinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Un systeme d'analyse automatique pour enregistrements ambulatoires

Magnetic ambulatory recordings were made on cassettes and analysed at 60 times the original recording speed using an analogical system. The amplitude of EEG was directly inscribed, in 6 different frequency bands, on paper. Limits of bands are 1, 2, 4, 8, 12, 24 (spindles) and 48 Hz. Included in the system are: automatic detection of rolandic paroxysms, detection of apneas after continuous recording of the respiratory movement and a cardiac frequency monitor. These additional parameters make the interpretation easier. The results and curves obtained are similar to those found in other methods elsewhere. Sigma rhythm or increase of delta activity during sleep are evident. Over long recording periods, research for respiratory apneas and cardiac rhythm variations is quick and easy to do. It is also possible to compare an entire day's paroxysmal activity on either right or left rolandic derivations. This system thus supplies information on various situations: disturbance of vigilance, study of interictal paroxysmal activity or detection of cardiac or respiratory pathology.

Sleep regulation after reduction of brain serotonin: effect of p-chlorophenylalanine combined with sleep deprivation in the rat.

Sleep was recorded in the rat after combined treatment with p-chlorophenylalanine (PCPA; 300 mg/kg) and 24-h sleep deprivation (SD) and then compared with sleep recorded after either treatment alone. PCPA alone reduced total sleep (TS), rapid eye movement sleep (REMS) per TS, as well as the power density of the EEG delta band (1.25-4.00 Hz) of non-REM sleep (NREMS). SD enhanced these sleep parameters and reduced the frequency of wake episodes. The combined treatment with PCPA and SD reduced TS and REMS/TS to a level similar to that induced by PCPA alone, and it increased delta activity to a level similar to that induced by SD alone. The frequency of wake episodes was reduced. It is concluded that essential aspects of sleep regulation are still functional during PCPA-induced insomnia. The sleep-inhibiting action of PCPA may be related to the hyperresponsiveness to stimuli rather than to the impairment of sleep regulation itself.

The calcium carbimide–ethanol interaction: Lack of relation between electroencephalographic response and cerebrospinal fluid acetaldehyde

Penetration of acetaldehyde into cerebrospinal fluid (CSF) was studied in healthy human volunteers during calcium carbimide-ethanol interaction. CSF was sampled via lumbar puncture and blood from a cubital vein. CSF and blood acetaldehyde concentrations varied from 1 to 41 and from 22 to 138 μmol/l, respectively. The results indicate that acetaldehyde penetrates the human blood-liquor barrier. Computer analysis of electroencephalograms (EEGs) recorded during the interaction showed reduction in alpha activity with a concomitant increase in delta activity. The changes were similar to those previously observed during ‘normal’ ethanol intoxication.

Delta sleep-inducing peptide (DSIP): EEG and motor activity in rabbits following intravenous administration

The synthetic delta sleep-inducing peptide (DSIP), a monapeptide, was injected intravenously in free moving rabbits (30 nmol/kg). In EEG tests, a significant increase in delta activity occurred within 5 h after injection of DSIP. Motor activity recorded simultaneously showed a slight concomitant decrease. These EEG and behavioral effects confirmed that DSIP also induces, when intravenously injected, orthodox slow wave sleep.

Pharmacokinetics and pharmacodynamics of ethanol, whiskey, and ethanol with n-propyl, n-butyl, and iso-amyl alcohols.

Plasma ethanol concentration, reaction time, and electroencephalogram (EEG) were recorded in 6 normal men after ingestion of ethanol along (Group 1), whiskey (Group 2), or a mixture of ethanol, n-propanol, n-butanol, and iso-amyl alcohol (Group 3). The peak plasma ethanol concentration and the total area under the plasma concentration:time curve of ethanol did not depend upon the type of drink given, but the half-life of the terminal exponential phase of ethanol elimination was longer in Group 3. In each study period reaction time increased, there was a relative increase in delta activity (2 to 3 Hz) and a fall in mean dominant frequency in EEG activity. The extent of increase in reaction time depended on the rate of increase in plasma ethanol concentration and correlated with the concentration of ethanol while the plasma concentration of ethanol was falling. Differences in the effects of ethanol between study periods were minimal.

Computer-determined EEG patterns associated with memory-facilitating drugs and with ECS

Cortical EEG patterns of rats were analyzed by computer following administration of analeptic drugs at doses previously shown to facilitate posttrial memory processes. The drugs produced an increase in the power of the EEG primarily by increasing the amount of activity in delta and lower-theta frequency bands. The increase in lower frequency theta was accompanied by a decrease in higher frequency theta, thus increasing the regularity in the theta band. Electroconvulsive shock, which disrupts posttrial memory processes, also increased delta activity, but it greatly lowered amplitudes throughout the EEG frequency spectrum. It is concluded that if any consistent relationship between the cortical EEG and posttrial memory processes exists, then increased amplitude and regularity in the delta and theta bands are associated with increased amounts of memory storage — at least in alert animals. Further studies are required to determine if a causal influence is involved in this correlation.