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W Scheuler

Publications and source records attributed to W Scheuler.

18 recordsLinked to original sources
PubMed1991

Short-term sleep EEG recordings after partial sleep deprivation as a routine procedure in order to uncover epileptic phenomena: an evaluation of 719 EEG recordings.

All night sleep deprivation prior to an EEG registration causes some inconvenience not only to the organization of the EEG department but presents a burden on the patients as well as their family members, and for these reasons is not suitable to be frequently employed as a routine procedure. As an alternative, we performed short-term sleep recordings in the early afternoon following a partial sleep deprivation of the patients during the preceding night. This method was well accepted by the patients and their family. Our only goal was to shorten the total time of night sleep using the following guideline: for very small children 22.00-06.00; for 4-14-year-old patients 24.00-06.00; and for patients older than that 01.00-06.00. 79.9%, out of 719 patients (573) who had been given the above instructions subsequently showed sleep patterns in their EEG. Additionally we had to administer an oral dose of promazine to only 67 patients. However, for the most part, patients showed only light sleep stages: 114 patients only reached sleep stage 1; 323 patients sleep stage 2; 88 patients sleep stage 3; and 48 patients sleep stage 4. As expected, REM sleep was never recorded. Nonetheless, in 32 out of 146 patients who were tired but unable to fall asleep, epileptic patterns could be provoked. In 636 patients, the EEG-recording after sleep reduction was ordered because of a suspected seizure disorder; in the remaining patients it was initiated solely because of sharp components in the routine-EEG. In 341 (53.6%) of the patients with suspected epilepsy, electroencephalographic activity indicative of a seizure disorder was activated. Such epileptic patterns were recorded almost exclusively in stages of waking, 1 and 2. Only in one out of the 124 patients who reached sleep stages 3 and 4 epileptic patterns were not seen until deep sleep was entered. We observed 2/s, 3/s and 6/s spike-and-wave complexes, sharp waves, spikes, polyspikes, groups containing remarkably sharp components and so called sharp vertex grapho-elements. Patients with suspected seizure disorders frequently show grapho-elements 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-and-waves in the same recording.

Adolescent↗
PubMed1991

[Pattern recognition techniques in sleep polygraphy].

The evaluation of EEG-patterns is usually accomplished by visual analysis. Nowadays however, even personal computers are fast enough for an efficient pattern recognition of EEG signals. Using sleep spindles and K-complexes as examples, our aim was to demonstrate how patterns can be detected in an EEG signal with a high degree of accuracy. Furthermore, recognition of K-complexes has been improved by applying an additional "adaptive algorithm" allowing individual adjustments to the signal's form and amplitude.

Algorithms↗
PubMed1990

Periodicity analysis of sleep EEG in the second and minute ranges--example of application in different alpha activities in sleep.

To investigate the temporal organization of EEG sleep activity in the second and minute ranges we developed a method which, based on Fourier transformation, allows the presentation of periodic oscillations of spectral power and coherence. The application of this method is demonstrated in 3 subjects with different types of alpha activity during sleep: (a) alpha-sleep pattern (a physiological variant of NREM sleep activity); (b) abnormally increased arousal alpha activity. The results show that differences in the temporal organization of these alpha activities can be determined with the following parameters: period length, duration of sequences with periodic activity, number and rate of these sequences, and proportion of periodicities generated simultaneously in the left and right hemispheres. The physiologically modulated periodicities of the alpha-sleep pattern are contrary to a stereotyped 40-60 sec periodicity of abnormal arousal alpha activity. Such abnormal periodicity corresponds to periodicities occurring in association with other sleep disturbances, such as sleep apnea or periodic movements in sleep. Periodicity analysis gives additional criteria for a more refined evaluation of normal as well as abnormal sleep structure.

Adult↗
PubMed1989

[The effect of age on sleep spindle and K complex density].

The amount of sleep spindles and K-complexes shows a great interindividual variety of combinations, such as many or few sleep spindles and K-complexes respectively. There seems to be no direct correlation between the amount of sleep spindles and K-complexes intraindividually. In our unselected population - age range between 18 and 77 years - the mean sleep spindle density is at 2.59 +/- 1.85/min and the mean K-complex density at 1.96 +/- .96/min stage 2. The diffuse individual distribution, however, does not reflect the age factor involved. The sleep spindle and K-complex density were practically half the amount for the age group above 50 years as compared to the age group of less than 30 years.

Adolescent↗
PubMed1989

[A system for continuous digitizing and evaluation of 32 biosignals from all-night sleep leads].

In all-night sleep recordings usually 12 to 16 channel electroencephalographs are used to record the electrical activity of the brain. A detailed analysis of EEG sleep activity, however, requires the inclusion of at least 19 electrodes placed according to the international 10-20 system in order to compare the variations of the activities in different brain areas. In addition polygraphic parameters such as ECG, respiration and actogram, to mention just a few, have to be recorded depending on the type of study. Therefore the number of recording channels has to be increased for a complete polygraphic investigation. We developed a 32 channel unit with a personal computer and corresponding hardware interfaces allowing the continuous digitalization of up to 32 bioelectrical signals throughout the whole night (8 hours). The recorded data can be presented graphically and evaluated according to the usual methods such as power spectrum, coherence and periodicity analysis. Additionally the use of algorithms for pattern detection permits automatic analysis of EEG segments regarding particular sleep patterns e.g. sleep spindles and K-complexes.

Electroencephalography↗
PubMed1989

[Polygraphic sleep data in AIDS patients].

Somnopolygraphic recordings were registered from 29 patients with AIDS, their age ranged from 20 to 55 years (mean: 40.9; median: 44). The patients represent the full range of cerebral disintegration representing the picture of a progressing destruction of physiological sleep organization. Some disturbances begin quite early and progress successively, such as the reduction of REM- and delta-sleep as well as the reduction of sleep spindle- and K-complex-densities. Other changes are not manifest until intellectual capabilities break down; they occur massively such as the shortening of real sleep time and the reduction of sleep stage 2 with a simultaneous increase in waking time. It is remarkable that despite the enormous REM reduction there is no suppression of REM periods corresponding to "REM sine REM". REM periods become very short at an early stage; this is not only because the patients awake more frequently and earlier from their dream periods.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Detection of brainstem lesions in multiple sclerosis: comparison of brainstem auditory evoked potentials with nuclear magnetic resonance imaging.

Topographical information provided by brainstem auditory evoked potentials (BAEPs) was investigated in 43 patients by comparison with cerebral nuclear magnetic resonance imaging (NMR). Lesions in the region of the brainstem auditory pathways were demonstrated by BAEPs in 44.2%, and in 39.5% by NMR. As regards brainstem levels, in 15/21 (71.4%) with abnormal findings at least one lesion was verified by NMR-matched BAEP results. The study confirms the topographical information provided by the BAEPs on the different levels of the brainstem, but not the assumption that generation of the BAEPs is predominantly ipsilateral. BAEPs retain their importance for the detection of disseminated lesions in the diagnosis of multiple sclerosis (MS) in the era of expensive imaging methods.

Adolescent↗
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↗
PubMed1979

[A contribution to the psychophysiology of infantile dysmegalopsy (author's transl)].

A 9 year old boy was able to evoke microptic experiences voluntarily. Clinical and historical signs of minimal brain dysfunction were present. An epileptic etiology could neither be proven nor ruled out. Synchronized EEG- and Video recording allowed us to analyze the EEG and the corresponding behavior by using sequential spectral analysis of the EEG data. Coinciding with a progressive increase in rhythmic 6-7 cps. activity we observed a behavior which appeared to correspond to a state of narrowed attention. He signalized the onset of a micropsy a few seconds after the transition from this pattern into one which showed a relative voltage decrease and the reappearance of some alpha-activity. The end was signalized by him coinciding with the recurrence of normal waking activity. Our findings--like those of others--suggest that the gradual development of hypnagogic phenomena is bound to a state of lowered vigilance. The reappearance of alpha activity and the voltage decrease seem to represent an unstable intermediary state with partial arousal preceding the restitution of normal wakefulness. Since the onset of the micropsy was signalized only after manifestation of the intermediary EEG-state, we conclude that partial arousal is a prerequisite for giving an indication of hypnagogic experiences in a quasi retrospective manner.

Arousal↗
PubMed1978

[On the effect of the antidepressant viloxazin on EEG and optimization of the system driver-vehicle-road (author's transl)].

The effects of a single dose of 100 mg 2-[(o-ethoxyphenoxy)-methyl]-morpholine hydrochloride (viloxazin) on EEG and optimizing control behaviour of drivers were investigated under double-blind conditions in 5 male subjects with many years' driving experience. The study was carried out on a special test course using a car equipped with measuring devices. The following signals were recorded: EEG and EOG, driving speed, steering torque, steering angle and angle rate, longitudinal and lateral acceleration, and yaw rate. As evaluated by means of spectral analysis with a subsequent principal component analysis the EEG showed an increase of the power in alpha- and beta-frequencies indicating a drug induced decrease of EEG vigilance. In correspondence the optimization of the system driver-vehicle-road was reduced indicating an impairment of the driver's control behaviour.

Adult↗
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↗
PubMed1976

[Psychophysiological studies of EEG, operational performance and the dynamics of vigilance regulation. II. EEG activity and reactivity during tracking performance in a control loop with varying degrees of difficulty (author's transl)].

In ten male students the EEG occipital activity was recorded during a visuo-motor task consisting of pursuit-tracking. The degree of task difficulty varied systematically depending on the modification of the transfer function of control element dynamics. The EEG data were evaluated by serial spectral analysis. The distribution functions of the total power estimates and their minima and maxima reflect the dynamics of the regulation of cortical vigilance and permit to differentiate the degree of effort which corresponds to the varying degree of task difficulty. The study of task-irrelevant acoustically evoked potentials showed that with increasing cortical activation the amplitudes of N1-P2 and P2-N2 are diminished. These results might suggest that evoked potentials induced by task-irrelevant stimuli can serve as indicators of the neuronal capacity available for information processing that is not task-oriented.

Adult↗
PubMed1976

[Signal analysis of EEG-changes induced by nomifensin - a new antidepressant (author's transl)].

Ten healthy volunteers received a single oral dose of 100 mg nomifensive, a new antidepressant (tetragtdriusiqyubikube deruvatuve; Hoe 36-984). The drug-induced effects on the EEG were compared with those of placebo. The statistically proved results show that nomifensine causes a distinct shift in vigilance with two different partial processes. After an initially occurring stabilization of the dominant alpha-frequency there appears a polyrhythmic disintegration of the alpha-rhythm with increase of slower and faster frequencies. At the same time a shifting takes place within the beta-range with increasing of 23.5-32.0 Hz-components. Accordingly it is evident that nomifensine results in a typical pharmaco-electroencephalographic profile.

Alpha Rhythm↗
PubMed1975

[Influence of repetition rate and pause upon the cortical potential evoked by various acoustic stimulation in man (author's transl)].

In agreement with earlier experiments an increase of amplitude of the medium components (80-250 ms: Non-Pon) with decreasing repetition rate or increasing interval between the stimuli (sinusoidal tones, white noise, craftsman noise) is observed. There is no influence of the variable intervals upon the off-effect, if sinusoidal tones and white noise are used. A small increase of the amplitude difference Noff-Poff results if bursts of craftsman noise are used for stimulation. The amplitude of a peak in the range 300-400 ms which can be regarded approximatively as the peak of the long lasting dc-component, related to the positive peak (Pon) around 200 ms shows also an increasing tendency if the interval between stimuli is enlarged. Pon itself is augmented if related to the preceding section before stimulus on-set. Therefore the increase of the slow component expresses only an increase of the positive component Pon or is based upon a dc-shift which is added to the preceding section as well as to the range of the dc-component beginning around 300 ms after stimulus on-set. Using only sinusoidal tones a reduction takes place of the amplitude of the potential evoked by a tone of constant duration if the silent pauses are smaller than 2500 ms. If the pause preceding a tone of constant duration is reduced down to 300 ms the decrease of the amplitude is around 50-60%. The amplitude of the off-effect however is not affected. Only if related on the positive component Pon the slow component shows a small decrease. If related on the preceding section there is no change caused by different pauses preceding a tone of constant duration. Both, the latency of on- and off-components is also not influenced by the variable pause. Only the peak of the slow component shows a shift in the way that there is a maximum if the duration of the pause corresponds to half of the interval. In this case there is also a clear maximum of the amplitude of the potential evoked by the tone of variable duration. The results throw some light upon the different origin of the components of the evoked response and the overlapping of dc-shifts.

Acoustic Stimulation↗
PubMedDate not supplied

EEG sleep activities react topographically different to GABAergic sleep modulation by flunitrazepam: relationship to regional distribution of benzodiazepine receptor subtypes?

Spectral analysis was performed to study the response of various EEG sleep activities to a modification of GABAergic sleep regulation by flunitrazepam. We observed sleep stage- and sleep cycle-dependent differences in the topographic distribution of the reactions. An increase in power density was found in the frontal regions for the alpha 2 and sigma 1 frequency band whereas a decrease in power density was emphasized in the posterior regions for the delta and alpha 1 frequency band. These topographic differences might be related to the regional distribution of benzodiazepine receptor subtypes.

Adult↗