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An investigation of certain electroencephalographic parameters recorded during 19 psychomotor attacks was made. Each attack had been recorded in full. Fourteen of the attacks were preceded by a temporal focus, 13 were provoked by hyperventilation, 18 were initiated focally, 9 were accompanied by seizure potentials, 7 revealed primary or secondary delta rhythms, and 8 were followed by temporal delta focus.
In a previous study (Harmony et al. 1993) we observed that the volume of lesions was correlated only with delta power, while the volume and density of edema showed a significant correlation with theta and alpha power, suggesting two independent origins of activity in the delta and theta bands in patients with space-occupying lesions. Our goal in this paper is to show, through a different technique, in a narrow band spectral analysis, that brain lesions are characterized by activity in the delta domain and that edema is better correlated with activity within the theta range. Frequency source analysis based on the Maximum Likelihood (ML) test for rejection of isotropicity was applied to the EEG at rest of 36 patients with space-occupying intracranial lesions. The ML test was rejected at frequencies below 1 Hz and in the low range of the delta rhythm in 31 patients. The origin of the equivalent dipoles at these frequencies was within the volume of the lesion in 27 patients. In 15 patients out of 19 with vasogenic edema the ML test was rejected at frequencies in the theta range. The equivalent dipoles at these frequencies were all within the volume of the edema.
Spike activity was studied in 95 neurons in the basal magnocellular nucleus in rabbits during spontaneous behavior and during performance of a conditioned operant response. Nearly half the neurons (48.4%) showed significant (p < 0.05) negative correlations between spontaneous discharges and the power of the frontal lobe EEG delta rhythm; most of these cells could be identified as cholinergic projection neurons. Neurons of this group had predominantly excitatory responses to the conditioned stimulus during performance of the operant task, while the responses to the conditioned stimulus of presumptively non-cholinergic neurons, not projecting to the cortex, were mainly inhibitory. The activatory responses of neurons in the basal magnocellular nucleus to the conditioned stimulus were markedly stronger while the animals performed the operant response as compared with performances in which there was no response to the conditioned stimulus. These results provide evidence that the basal magnocellular nucleus supports the level of waking and attending required for performance of operant conditioned reflex activity.
In this report 52 patients meeting the criteria of centrencephalic myoclonic-astatic petit mal (10) at the beginning of petit mal are included. The results of clinical and encephalographic follow-up examinations are as follows: 1) The type reported here apparently has a petit mal course with peculiar characteristics, it therefore must be separated from Lennox syndrome: centrencephalic myoclonicastatic petit mal, pyknolepsia, bilateral myoclonus (impulsive petit mal). It should file under generalized primary petit mal epilepsy. 2) It is primarily defined by its EEG marker: "centrencephalic" EEG pattern (irregular and/or regular spike-wave groups, photosensibility and abnormal theta- and/or delta-rhythm). Rarely (33%) minor cerebral organic lesions as additional pathogenetic factors are uncovered by clinical and electroencephalographic examinations. 3) The clinical picture is characterized, aside from myoclonic and/or astatic seizures, by frequent absences (80%), rare tonic seizures (6%), petit mal status (25%) and mostly generalized grand mal seizures (62%). 4) There are changes of the course of the disease to Lennox syndrome (N = 6) in in children suffering from marked cerebral organic lesions at the onset of petit mal and in development of severe epilepsy. 5) Least favorite markers with respect to prognosis are concomitant grand mal seizures (p = 0,05), petit mal status (p = 0.008), additional 2/sec spike wave-pattern (spike wave Variant) in the EEG (p = 0.002) and previous seizures with focal signs. Favourite outcome of epilepsy are frequently connected to missing cerebral organic lesions (p = 0.05).
A model of thalamocortical relay neuron is studied to assess whether a 7-14 Hz (spindle) oscillation and a 0.5-4 Hz (delta) oscillation may result from the interplay between a T-type calcium current and a non-specific cation sag current. With moderate change of membrane parameter values, the model neuron can exhibit both the spindle and delta rhythms, at different levels of hyperpolarization; only the slower (delta) one or none. In the case when the model neuron is not intrinsically oscillatory, its response to rhythmic hyperpolarization is complex, and displays the "intermittent phase-locking" phenomenon where bursts of Na+ action potentials occur infrequently but their occurrence is phase-locked to the rhythmic input. The rhythmic bursting, whenever possible, is shown to emerge (bifurcate) from a subthreshold oscillation. Near the bifurcation chaotic discharge patterns are observed, where spikes occur intermittently at randomly chosen cycles of a mostly subthreshold slow oscillation. Furthermore, when both the spindle and delta modes can be realized, the transition between the two appears as a sudden drop of the rhythmic frequency with increased hyperpolarization. The T-type calcium current and the sag current may explain the "intermittent phase-locking" phenomenon that is characteristic to thalamic relay neurons during spindle oscillation and provide a cellular basis for the 7-14 Hz rhythm and the slower 0.5-4 Hz rhythm.
The purpose of this study was to assess quantitative electroencephalography (q-EEG) in 10 healthy beagle dogs under propofol anaesthesia in order to determine objective guidelines for diagnostic electroencephalographic (EEG) recordings and interpretation. The basic pattern after preliminary visual examination of EEG recordings was characterized by spindles, k-complexes, vertex sharp transients, and positive occipital transients that were superimposed on the slow background activity. The results of the q-EEG were characterized by the prevalence of slow rhythms delta and theta, both in absolute and relative power spectrum analysis, while fast rhythms (alpha and beta) were poorly represented. The distribution of single frequency bands was widespread for delta, focal for frontal and central for theta, as well as for most alpha and beta patterns. The present study has shown that the use of quantitative EEG gives information on the frequency content of the bio-electrical activity and defines the distribution of the single frequency bands under a standardized anaesthetic protocol.
Investigations were carried out in 50 patients with epilepsy who had been subjected previously to careful clinical examination. For the investigations the preparation Gamma-OH EGIC was used in doses of 0.03 g/kg of body weight in rapid intravenous injection. The preparation modified rapidly the EEG tracings which were divided into 4 phases: 1) phase of initial resting record, 2) disappearance of alpha rhythm with increase of medium and low-voltage theta rhythm, 3) high-voltage phase resembling sleep activity with prevalence of delta rhythm, 4) phase of desynchronization--return of normal activity. Out of 50 epileptics in 31 cases temporal-lobe epilepsy was present, in 15 the seizures and EEG changes were generalized, in 4 cases focal non-temporal-lobe epilepsy was recognized. Administration of Gamma-OH to epileptics caused in 100% of cases a modification of the initial tracings and in 84% activation of EEG changes mainly with activation of focal slow-wave activity; in cases of minor absence attacks the drug always induced paroksysmal activity. The preparation is safe and non-toxic and may be used in outpatient clinics. It seems that activation of EEG changes in epileptics by Gamma-OH administration may be due to disturbances of the equilibrium between the structures activating and inhibiting the reticular formation of the brain stem and cerebral cortex.
A study concerning the clinical and electroencephalographic effects of bromocriptine, on senile dementia (senile degenerative, vascular and mixed dementia), was carried out on 22 patients. The protocol for this clinical experiment was inspired from genetic psychology. A posology of 5 milligrams was generally used. The clinical results show an improvement in the motor, operative, and memory functions but especially in the sphere of emotion and behaviour. The electroencephalographic results show in 2/3 to 3/4 of the cases, the reappearance of alpha rhythm, an improvement in the arousal reaction and the reduction of the delta rhythms. The comparison between the clinical and the electroencephalographic results shows an appreciable electro-clinical concordance.
The effect of bromocriptine on the course of dementia in the aged is reported by the authors. This study is based on a protocol taken from genetic psychology and concerns 25 patients. A posology of 5 mg was generally used except in 4 patients who received 10 mg. The clinical results show improvement in the motor, operative and memory functions as well as in affect and behavior. The electroencephalographic results show in 2/3 to 3/4 of the cases, the reappearance of alpha rhythm, an improvement in the arousal reaction and the disappearance of the slow delta rhythms. The comparison between the clinical and the electroencephalographic results shows a remarkable electro-clinical concordance.
The search for neurophysiologic correlates of attention and working memory dysfunction in families with schizophrenia, 55 patients with schizophrenia and schizoaffective psychosis, 91 unaffected first degree relatives and 48 mentally normal subjects without family history of mental disorders have been studied. Changes in power of 5 EEG frequency bands in 16 records during serial mental arithmetic tasks were analyzed. Abnormalities in EEG reactivity were found both in patients and their relatives. Both groups were characterized by diffuse elevation of delta-rhythm power, the signs of hypoactivation and inversion of reaction asymmetry for different rhythm bands in the frontal area. In relatives, more pronounced attention dysfunction corresponded to more expressed abnormalities in EEG reactivity. Moreover, patients demonstrated insufficient depression of alpha and fast waves activity in the posterior cortex areas relevant to arithmetic activity. The results obtained allow considering an impaired reaction of alpha and fast rhythms inhibition in the posterior cortex areas as characteristic of the disease, and diffuse elevation of delta-waves power and frontal lobe hypoactivation with the inversion of reaction asymmetry as familial features that might reflect an impact of the factors predisposing to psychosis. This predisposition emerged during the cognitive task involving sustained attention and working memory.
In order to reveal correlations between disturbances in higher cortical functions and characteristics of electrical activity 70 patients with pathological foci in the hypothalamic regions were examined using computer data processing. Destruction of the normal intercentral relations between EEG rhythms develops under the influence of the hypothalamic focus. The process builds up with the aggravation of cortical disorders (mnestic, emotional-affective, consciousness oppression with sleep inversion). General decrease of EEG coherence is observed with the highest destruction of correlations in the frontal cortical areas. The structure of high-frequency alpha-rhythm becomes deranged even in slight cortical disorders, its coherence decreases predominantly in the frontal cortical areas. With intensification of the pathological process in the focus, the stage of delta-rhythm coherence increase is observed and at the background of general destruction of correlations new, pathological intercentral relations develop. Using a BRAINLOC computer technique "sources" of the delta- and theta-activity have been localized in the medio-basal brain regions. The area of localization is specific for hypothalamic lesions. The "source" is mostly expressed in the slightest pathology of higher cortical functions. With aggravation of the process in the hypothalamic pathological focus and further derangement in the cortical functions expression of the "sources" reduces up to their complete disintegration in coma.
The author presents the hypothesis that reduced delta EEG power observed in cocaine withdrawal is related to changes in dopamine (DA) transmission related to cocaine sensitization. Evidence for this hypothesis includes the topographic anatomical correspondence between the putative site of delta generation and the cortical terminal field of the mesotelencephalic DA system, as well as the laminar distribution and ultrastructural features of DA terminals in frontal cortex that appear to be adapted to the modulation of the delta rhythm, a global forebrain EEG mode. The effect of DA on membrane conductances of individual pyramidal neurons also suggests that DA exerts a significant influence on delta power by modulating the transition between global and local EEG modes. Access to a neural correlate of sensitization via noninvasive EEG methodology could be useful in investigating the relationship of stimulant sensitization to the clinical syndrome of cocaine dependence.
Electrical activity of the cerebral cortex and lateral hypothalamus was recorded in 2 groups of alcoholized rats 1) in motivation state induced by one-day alcohol deprivation and 2) after long-lasting free consumption of alcohol. Non-alcoholized rats served as the control. Neocortical and hypothalamic EEG in non-deprived rats with pronounced attraction to alcohol consumption did not differ from the control. Power spectra of this activity had the peaks in the delta band. The amplitude of the delta rhythm in the cortex was twice as high as that in the hypothalamus. During alcohol deprivation power spectra of the neocortical and hypothalamic EEG were alike, and in most of the cases spectral density in the hypothalamus (with the delta peak) exceeded the cortical one. Termination of the alcohol deprivation by ethanol injection per rectum induced in some animals reversible spectral changes in the hypothalamic EEG and well-pronounced shift of its peak towards the theta rhythm.
The perception of time by humans was studied by the method of time reproduction. The EEG was recorded in Os, Od, Cs, Cd, Fs and Fd derivations. The relative EEG spectral power was determined in the delta-1, delta-2, theta, alpha, beta-1, and beta-2 ranges. All the subjects were divided in two groups: I--those who reproduced time-intervals with a delay, and II--those who were ahead in their reproduction. The spectral power of the delta-rhythm was significantly lower and that of the beta-rhythm higher in the subjects of the I than of the II group. In subjects of the II group total power of the beta range (beta-1 + beta-2) was significantly less than that in the delta-range (delta-1 + delta-2). This ratio was inverse in subjects of the I group. The described relationships were expressed both in the background EEG and during functional loads in all the studied derivations.
Among viral diseases, subacute sclerosing panencephalitis is one of the most frequent in Iran (more than 300 cases in two neurological centers and for the last ten years). This paper is devoted to an electroencephalographic study of 40 patients: visual analysis of EEG rhythms (frequency, amplitude, lability, morphology), effects of activation methods, description of pathological EEG patterns (periodic paroxysmal complexes in 38 cases; slow or fast spikes, polyspikes and bifrontal or diffuse spikewaves in 9 cases; localized comitial abnormal patterns in 5 cases; bifrontal delta rhythm in 13 cases). From this description, we suggest an hypothesis of a diffuse localisation at the origin of periodic paroxysmal patterns: the periodic discharge of immune complexes from cerebral tissue into the cerebral circulation would constitute a synchronizing system which periodically modifies the blood-brain barrier permeability.
The EEG spectral structure was studied in 30 healthy adult subjects during formation, realization of the verbal set and its disappearance. The subjects were divided in two groups according to the set stability: I-with the stable, II-with the unstable set (the set was maintained during 6-30 or 1-3 trials, respectively, in the subjects of the I and II groups). The background EEG records in the subjects of the I group were characterized by the dominance of the alpha-activity. Changes in the delta-rhythm power turned to be the most informative at different stages of the experiment. During the formation of the set its power was substantially lower in the subjects of the I than of the II group. During disappearance of the set effect there was a significant decrease in the delta-power in subjects of the II group. It is assumed that the formation of the stable fixed set is a stabilizing factor in behaviour which is reflected in the electrical activity of the cortex.
Power and topographic distribution of the EEG rhythms (delta, theta 1, theta 2, alpha, beta 1, and beta 2) were compared with the reactive and personal anxiety levels (by Spilberger) and parameters of subjective emotional semantic space (obtained by the method of subjective scaling). A general decrease in the EEG power was observed in reactive depression, with the exception of the theta-rhythm, the power of which was higher than that in healthy persons. The increase in the theta 2 power in depression was correlated with activation of the right frontal area ("the zone of negative emotions"), and its decrease was associated with activation of the left frontal area ("responsible" for positive emotions), enhancement of positive emotions in semantic emotional space, and with a decrease in personal anxiety. High alpha activity in healthy persons was negatively correlated with the activation of the "zone of negative emotions" while a decrease in the alpha-rhythm power was associated with anxiety enhancement and decrease in contribution of positive emotions in the semantic space.
The EEG power spectral analysis of 8 patients with a definite sylvian ischemia, the standard EEG of which was normal, was determined in comparison with the date of a control group (N = 14). We calculated the right-left power spectral differences in 4 symmetrical bipolar leads for 5 rhythms (delta: 1.2-3.1 Hz, theta: 3.5-7 Hz, alpha: 7.4-12.3 Hz, beta 1: 12.9-14.1 Hz and beta 2: 15.2-17.2 Hz). For each patient, the spectral difference is measured in comparison with the normal range of the control group with an alpha risk of 5%. There are 54 asymmetries favouring the lesioned side (mostly in 5 patients) and 6 the opposite, without predominance of a particular rhythm with the exception of the beta 2 rhythm which presents no asymmetries.