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Biomedical subjects

S Kubicki

Publications and source records attributed to S Kubicki.

At least 37 records · Page 2Linked to original sources
PubMed1989

[Spectral power density and coherence in sleep EEG in patients with acquired immunodeficiency syndrome].

15 male AIDS-patients from 26 to 55 years (mean 41.8 +/- 8.5) with various cerebral manifestations had a whole-night-sleep-EEG registration. As control the recordings of 15 age-matched volunteers (26-55 years, mean 41.8 +/- 9.8) were examined. Spectral characteristics of elementary EEG-epochs of 40 s length were computed, and sleep staging was performed visually for these intervals. The spectral power density of eight EEG-derivations (left and right frontopolar, frontal, central and occipital electrodes, reference montage to the ipsilateral Cb) were measured (sampling rate 64(-1) s, spectral resolution .25 Hz, frequency range from .25 to 24 Hz). Interhemispherical coherences of the frontal and occipital derivation pairs, and intrahemispherical fronto-occipital coherences of the left and right hemisphere, were computed. In the patients the frontal power density of NREM sleep showed lower values in the frequency range of 10 to 14 Hz. In central and in occipital derivations the power density between 12.5 and 15 Hz was lower in the patients, but the difference was less accentuated. The spectral power density of REM sleep showed similar characteristics in both groups. The interhemispherical frontal coherence of the whole frequency range below 13 Hz was markedly lower in the patient group. This was true for the NREM sleep, and, slightly less, for the REM sleep, too. The interoccipital spectral coherence was generally slightly lower in the patient group; the difference was most clearly in the 12.5 to 15 Hz range of NREM sleep.

Acquired Immunodeficiency Syndrome↗
PubMed1988

[Changes in the EEG background rhythm and in the hyperventilation effect at different stages of HIV infection].

The visual evaluation of 370 clinical EEGs of 125 patients in different stages of the HIV-infection as well as 42 HIV-seronegative volunteers of the same high risk population (male homosexuals) proved the increasing appearance of CNS dysfunction with progression of the disease. An especially established hyperventilation-index for a semiquantitative evaluation of hyperventilation response showed an increase of slow-wave activity in the course of the infection. The appearance of slow-waves as well as a significant slowing of background activity in advanced stages of the HIV-infection can be regarded as unspecific signs of a beginning diffuse functional CNS disorder caused by a direct affection of the CNS through the Human Immunodeficiency Virus (HIV). The EEG changes in early stages are not specific as to their causative agent and do not allow the distinction between primary and secondary CNS involvement. The changes may precede clinical-neurological alterations.

AIDS-Related Complex↗
PubMed1987

On the distribution of REM and NREM sleep under two benzodiazepines with comparable receptor affinity but different kinetic properties.

Two clinical-pharmacological investigations were performed to give a retrospective and explorative record, based on electroencephalographic parameters, of spindle density and REM distribution in the first and second halves of the night under a short-acting (triazolam) and medium-acting (lormetazepam) benzodiazepine. A further aim was to determine whether a suitable dose of a short-acting benzodiazepine could lead to a REM suppression in the first sleep cycles and a REM compensation in later sleep cycles on the same night. Since sleep spindles are increased and rapid eye movements reduced under benzodiazepines, the two phenomena were respectively taken as indicators of drug effects on NREM and REM sleep. According to the receptor affinity of the two substances, dosages of triazolam and lormetazepam ought to be equieffective in a ratio of about 1:2. Yet clinical experience has shown that a ratio of 1:4 (0.5 mg triazolam vs. 2 mg lormetazepam) gives the doses that are equieffective and which are widely used in clinical practice. The changes in the number of sleep spindles and rapid eye movements documented the different kinetic properties of the two substances. Even after clinically equieffective doses, the changes in the parameters were less marked under lormetazepam than under triazolam. This suggests that the two benzodiazepines different effects on spindle and REM distribution were not attributable to their kinetics, but that pharmacodynamic aspects must also be considered, even if this does not fit in with the prevalent picture of the benzodiazepines mechanisms of action.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

COMSTAT rule for vigilance classification based on spontaneous EEG activity.

For the classification of sleep stages, international standards based on visual EEG analysis have been established and are in common use, although we are well aware of their limitations. Several authors have suggested different procedures for classifying the stages of vigilance during the waking stages. No universally accepted paradigm, however, has yet been developed. The proposed vigilance classification procedures are based either on visual or automatic analysis procedures. Even though the EEG activity and patterns that reflect vigilance changes have been identified and described as indicators of the state of alertness, opinion is divided on how these should be combined in a vigilance classification rule. Automatic methods, on the other hand, have up to now used only part of the information available, the relationship of which to vigilance indicators has only been partially explored. The COMSTAT (Dept. of Computation and Statistics, AFB-Arzneimittelforschung, Berlin, FRG) rule combines visual and automatic analysis procedures. Different vigilance-dependent EEG patterns, such as the proportion of occipital background rhythm under resting conditions and its replacement by either faster or slower waves, the frequency range of the occipital rhythm and the anteriorization phenomena, have been used as information for a latent class analysis (LCA5) with 5 classes (stages of vigilance). There is a high correlation between the results of the LCA5 with visual classification rules made by experts. Using a robust discriminant analysis function which takes into account prior probabilities of the classes, and with a linear cost function for misclassification, an automatic rule with power spectrum variables was fitted to the results of the LCA5. Reclassification and split-half classification showed a high overlap between LCA5 and automatic classification. The result of this procedure is a new vigilance classification rule that is based on an objective mathematical rationale for the combination of different vigilance-indicative EEG activities and patterns but which can be applied to power-spectral estimators in an automatic EEG analysis procedure.

Aged↗
PubMed1987

[Cortical distribution of 2 delta frequencies in slow wave sleep].

Many persons show two different types of delta-activity during synchronized sleep; these can already be differentiated visually as follows: one is located over the anterior brain areas, has a high frequency and is monomorph, the other one is located over the posterior brain areas, has a low frequency and is polymorph. However, both rhythms overlap considerably regarding their cortical distribution. The high high frequency delta-activity usually ranges from 1.5-2.9 Hz with a maximum at 2Hz; the one with low frequency ranges from 0.1-1.4 Hz with a maximum at 0.9 Hz. The interhemispheric coherence of the delta-activities is high with 0.7-0.9; for the anterior regions it is slightly higher than for the posterior ones. The intrahemispheric coherence is low, as was to be expected, and it is less than 0.3.

Adult↗
PubMed1987

[Effect of lormetazepam, triazolam and flunitrazepam on rapid eye movements, K-complexes and sleep spindles in normal probands].

"Equipotential" doses of lormetazepam, triazolam and flunitrazepam were tested regarding their influence on K-complexes, sleep spindles and rapid eye movements. The receptor affinity was used to determine the equipotency. In this respect triazolam, lormetazepam and flunitrazepam show a relationship of 1:2:4. Lormetazepam, however, showed only slight changes of the three neurophysiological parameters even when given as double dosage. Triazolam and flunitrazepam reduce K-complexes considerably, increase sleep spindles enormously and reduce REM activity markedly; both substances suppress the first REM period, flunitrazepam even the second one. All three of the benzodiazepines have the same effect on the dissociation of K-complexes and sleep spindles; epochs with K-complexes or sleep spindles are favored compared to epochs with K-complexes and sleep spindles. The general reduction of K-complexes and the increase in sleep spindles can be interpreted as a sleep protective function. When deciding on the dosage, however, REM-suppression should be used as a guide since it has the strongest effect on the cyclic structure of sleep which nowadays is considered to be the safest evidence of well balanced sleep behavior.

Adult↗
PubMed1986

[The 4 second sleep spindle periodicity].

Polysomnographic EEGs were recorded from 12 adult volunteers between the ages of 20 and 50 years. They were given placebo, pentobarbital, carbromal, methaqualone, flunitrazepam, lormetazepam and triazolam. The visual evaluation was aimed at finding periodic sequences of centro-parietal sleep spindles at 13-15/s. Four consecutive spindles following each other regularly were defined as the shortest sequence. Placebo showed the following results: a considerable interindividual variance with 2 to 6 such sequences on the one hand and 25 on the other hand for each night. sequences with six periodically consecutive spindles dominated; the longest sequence contained 15 spindles. the inter-spindle distance was 4 seconds (m: 4.09; mean 4.14 s). All hypnotics caused an increase in periodic spindle sequences. Volunteers with a low tendency to have periodic spindle sequences remained at the lower end of the scale when taking hypnotics. Hypnotics increased the amount of longer spindle sequences, however, the average was still at sequences of 4-11 consecutive spindles. The inter-spindle distance became longer with all hypnotics; 4.34 s (carbromal) up to 4.58 s (flunitrazepam). Volunteers with a low tendency to have periodic spindle sequences showed shorter distances between spindles vice versa. Benzodiazepines do not reveal any characteristics due to their pharmacokinetic structure.

Adult↗
PubMed1984

[Registration of visual evoked neuromagnetic fields following partial field stimulation of the fovea].

Visual evoked neuromagnetic fields were recorded after stimulation of the right and left foveal half-field and of the right lower and upper quadrant. A contralateral topography of the dominant complex of the visual evoked field was measured on the skull after right and left half-field stimulation. After switching from the right half-field stimulation to the stimulation of the right quadrants we observed large individual differences in our subject group. A possible morphological explanation is that the more elementary stimulation in the quadrants is connected with a greater number of dipole orientations as compared with the less elementary stimulation in the half-fields.

Adult↗
PubMed1984

[Changes in the length of sleep cycles during administration of flurazepam and lopirazepam].

The influence of narcotics on the duration of the ultradian NREM/REM cycle can be clearly recognized only when the first, particularly instable cycle is also included in the evaluation. A study with Lopirazepame and Flurazepame showed that compared to placebo Lopirazepame prolonged the first cycle particularly. In contrast with Flurazepame the first, but mainly the second cycle was shortened, and not until the third NREM/REM cycle the duration was compatible with that of placebo and Lopirazepame. The result is, that in nights of the same length Flurazepame shows a half or one cycle more compared to Lopirazepame.

Adolescent↗
PubMed1983

[Genetic basis of beta patterns of the EEG in the adult].

Stable EEG-characteristics of a normal healthy person can be subdivided into posterior basic rhythms and normal variants. Posterior basic rhythms are: alpha type, theta type, occipital beta type and diffuse beta type. Normal variants--accessory characteristics without pathological significance--are: occipital theta variant, mu waves, beta bursts over the frontal areas, lambda and sleep lambda waves as well as subvigil beta bursts. It has been proven that posterior basic rhythms as well as normal variants--the latter only to some extent Both types of posterior beta rhythm show a high correlation with low voltage and are inherited in a simple autosomal dominant mode. Both types of frontal beta bursts are rare normal variants, and show characteristics which can be easily distinguished from each other. Type 1 is inherited in a simple autosomal dominant mode whereas type 2 is inherited in a simple dominant mode. Subvigil beta bursts are found in 10% of the population as a stable characteristic during light NREM and during REM sleep. A sleep dominant mode of inheritance--although quite likely--has not yet been proven even though this characteristic shows a marked individual stability.

Adult↗
PubMed1983

The alpha-sleep pattern. Differentiation from other sleep patterns and effect of hypnotics.

We observed the alpha-sleep pattern in 6 out of 44 subjects who offered neither somatic nor psychological complaints. All of the 6 subjects demonstrated the pattern consistently over a period of several years. 14 of the polygraphic sleep EEGs were recorded when free of any drugs, 10 after administration of benzodiazepine hypnotics. The alpha-sleep pattern is superimposed on all the regular patterns during any of the different sleep stages, and shows a cyclic representation with an increase correlating to the delta-sleep stages 3 and 4. It can be differentiated from other activities due to its localization, frequency characteristics, occurrence in relation to different sleep stages, and modification under the influence of benzodiazepine hypnotics. In contrast to the sigma-spindle activity, the alpha-sleep pattern is reduced with these drugs. Regarding the functional significance of the alpha-sleep pattern one might consider the possibility that it indicates a partially heightened level of sleep depth.

Adult↗
PubMed1982

[Comments on the rules by Rechtschaffen and Kales about the visual scoring of sleep EEG recordings].

The rules by Rechtschaffen and Kales present numerous problems; they sometimes even contradict physiological facts. This is due on the one hand to the manual being limited to central leads only, and on the other hand to rules which are partly too narrow, partly too broad and partly too complex. Furthermore, there are situations and physiological facts for which the manual does not have any rules. The exclusive evaluation of central leads has to result in a different scoring for numerous epoches of stages than an evaluation of leads from all hemisphere electrodes. In addition, frontal or occipital graphoelements such as mitten-pattern and sleep lambda are not even included. It is often difficult to make a distinction between an "alpha-sleep type" and pre-arousals (micro-arousals); the latter also applies to alpha groups in REM sleep. In particular however, if frontal, parietal and occipital leads are included, then the stage 2, above all however stages 3 and 4 will be represented more frequently, as sigma spindles, K-complexes and delta-waves are frequently found in a recognizable form only in the non-central leads. Further difficulties result from different paper speeds of 15 or 10 mm/s and from the rule concerning the allocation from stage 1 to stages 2 or REM.

Electroencephalography↗
PubMed1982

["Epileptic" spiked vertex potentials in brief sleep after sleep reduction].

Patients with suspected seizure disorders frequently show graphoelements which can be interpreted as the expression of a disposition for epilepsy. These sharp vertex elements were evident in 54 out of 719 short term sleep recordings, more often in children than in adults. 49 times they coincided with typical epileptic discharges such as sharp waves, spikes or spike waves in the same recording.

Adolescent↗
PubMed1981

[The use of electrophysiological techniques to project typical psychotropic drug effects: some examples (author's transl)].

A long existing hypothesis, i.e. that the EEG effects, in lead O2A2, of typical psychotropic drugs are substance class specific, when given as single oral dosages to healthy volunteers, is discussed. Using the technique of pharmacoelectroencephalograhpy, five typical representatives of neuroleptics, anxiolytics, antidepressives, psychostimulants (Fig. 2) as well as placebo were investigated in 75 volunteers, each receiving one representative of each substance class in a double blind 5-fach change over latin square design (Fig. 3). A five minute EEG record for lead O2A2 was obtained pre, 1 h and 3 hrs post drug intake unter RR (Relaxed Recording) conditions. Typical samples of th EEG records are shown in Figs. 4--7. Parametrisation was done using power spectrum analysis. Then 3 x 7 target variables were formed--six relative power values in predetermined frequency bands and the total power between 1.5 and 30.0 Hz for 3 occasions of measurement (Fig. 4--7). Using a (five-group) linear discriminant analysis the substance effects on the EEG were transformed into 5 probability measures for the five substance classes (Fig. 4--7). The present paper should provide a demonstration of some typical examples, using single subjects, of the projection of substance effects onto an electrophysiological level using a vector of 21 components (7 target variables for 3 occasions of measurement) as can be seen from Table 1. Furthermore, the transformation into probability measures of the five substance classes are shown in Table 2. Table 3 shows five examples of projections of substance effects, which do not fit into the classifications to which they belong. An attempt is made to explain, whether single target variables from the power spectrum can contribute differently to the discrimination between single substances of different substance classes. Within the accepted system of 4 psychotropic drug classes, the following variables seem to be of importance: a) The benzodiazepine anxiolytics show a marked increase in beta F1 (12.0--18.0 Hz) power and activity and, related to sedation, an increase in delta F-power and a decrease in alpha-power; b) The psychostimulants of the amphetamine type show an increase in total power and alpha-power, an increase in the power of the frequency ranges near to the alpha-band (slow beta, fast theta) and a decrease in delta F (1.5--5.5 Hz)-power, when delta F-power is high in the pre-values, indicating a stabilization in vigilance; c) The neuroleptics show a marked increase in theta F (5.5--8.5 Hz)-power, some increase in the delta F--and a decrease in the beta F1-and beta F3-power; d) Tricyclic antidepressants show an interaction between delta F-theta F-, alpha- and beta-power, in the sense of a dissociative shift in vigilance.

Adult↗