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Biomedical subjects

W Szelenberger

Publications and source records attributed to W Szelenberger.

At least 19 recordsLinked to original sources
PubMed2003

Task related difference EEG spectrum--a new diagnostic method for neuropsychiatric disorders.

ERDS is a new method that was developed to detect EEG changes during a short mental task (reverse counting). It is recommended for testing cognitive EEG in organic mental disorders. The essence of the task situation is that it needs continuous mental work during a short period of time. The level of task difficulty must be adapted to each patient's actual mental capacity. To preserve continuity of the mental work, the level of difficulty might be changed instantly by the EEG technician in case of a longer break or multiple mistakes by the subject in the task. For analysis, artifact-free EEG sections are manually selected. Differences of pre-task and post-task EEG power spectra (ERDS) and differences of the peak and mean frequencies are calculated. Based on our initial experience on 100 ERDS tests, this method demonstrates cognitive EEG changes related to the task. Each patient's pre-task EEG serves as control data that is compared to post-task changes. Hence, confounding effects on the ERDS test are minimal, i.e., the effect of individual EEG features or those EEG signs of the disease or therapy that are independent of cognitive functions. Therefore, ERDS test results can be considered as markers of cognitive state in diverse pathological conditions. They also enable us to follow changes during the spontaneous course of mental illness or due to therapeutic interventions. Appropriate instruction of patients about the task, attention of the technician in order to preserve the patient's continuous mental work, and to insure patient compliance are very important. Further investigation is necessary for validation of the method and to build a database of tests on healthy population of different age groups and of patients with different psychiatric conditions. Standardization of the test is essential for the introduction of ERDS to the every-day routine of clinical neuropsychiatry.

Cognition↗
PubMed2003

A simple system for detection of EEG artifacts in polysomnographic recordings.

We present an efficient parametric system for automatic detection of electroencephalogram (EEG) artifacts in polysomnographic recordings. For each of the selected types of artifacts, a relevant parameter was calculated for a given epoch. If any of these parameters exceeded a threshold, the epoch was marked as an artifact. Performance of the system, evaluated on 18 overnight polysomnographic recordings, revealed concordance with decisions of human experts close to the interexpert agreement and the repeatability of expert's decisions, assessed via a double-blind test. Complete software (Matlab source code) for the presented system is freely available from the Internet at http://brain.fuw.edu.pl/artifacts.

Algorithms↗
PubMed2001

Event-related current density in primary insomnia.

Using Low Resolution Electromagnetic Tomography (LORETA), event-related current density was investigated in 14 patients with primary insomnia and 14 controls matched for age, gender and education level. All subjects were rated on the Athens Insomnia Scale, the Hyperarousal Scale, the Hamilton Depression Rating Scale and the Beck Depression Inventory. They also completed the Selective Reminding Test and the Continuous Attention Test. Only minor elevations on depression scales were found in patients. The Continuous Attention Test did not reveal any between group differences. However, insomniacs required more trials before all the Selective Reminding Test items were learned. Insomniacs showed less event-related current density in orbitofrontal, medial prefrontal and anterior cingulate cortex, i.e. brain regions of relevance for cognition and affect. Earliest group differences appeared in the P1 time range and then were observed at the N1, N2 and P3 stages of stimulus processing. These stimulus processing differences correlated most consistently with severity of insomnia. Neuropsychological impairment correlated most strongly with less current density in Brodmann area 10.

Adult↗
PubMed2000

Severity of insomnia correlates with cognitive impairment.

INTRODUCTION AND METHODS: Cognitive deficits in insomnia have been already reported (5), however, a correlation between cognitive impairment and severity of insomnia was not as yet studied. Sixteen not medicated patients with primary insomnia according to DSM-IV (4), 7 men an 9 women, of mean age 40.8 year, were compared to 16 controls, matched according to age, sex and education. Standard polysomnographic data (PSG) were recorded. The next day all the subjects completed Athens Insomnia Scale (AIS) (7), Hyperarousal Scale (HS) (6), Hamilton Depression Rating Scale (HAM-D), Beck Depression Inventory (BDI), Multiple Sleep Latency Test (MSLT) (3), Continuous Attention Test (CAT) with simple reaction time (RT) (8) and Selective Reminding Test (SRT) (2). RESULTS AND DISCUSSION: The psychophysiological differences between patients and controls are shown in Table I. HAM-D and BDI scores were elevated in patients, although none of the patients met clinical criteria of depression. Insomniacs did not differ in the immediate recall, but the number of repetitions necessary to learn all the items of SRT was greater in patients. Insomniacs usually complain of poor performance, however, learning impairment has not been documented in insomnia. Degree of the learning impairment correlated with insomnia score (Fig. 1). Cognitive deficit cannot be due to a daytime sleepiness because sleep latency in all MSLT sessions was not shorter in insomniacs. No correlations between results of SRT and standard PSG parameters were found, in accordance with the thesis that subjective feeling of nonrestorative sleep and other accompanying deficits are only symptoms of an underlying 24-hour disorder (1).

Adult↗
PubMed2000

[Localization of attention related cortical structures by evoked potentials].

Attention is an ambiguous concept, difficult to direct implementation in neurophysiological studies. The paper presents application of the Continuous Attention Test (CAT) items as stimuli in event related potential (ERP) studies on attention. Stimuli with high demand of attention result in enlarged N1 component in occipital derivations. Spatial analysis revealed increased positivity in frontal derivations. Three-dimensional image of cortical current density by means of Low Resolution Electromagnetic Tomography (LORETA) revealed sources of N1 component in occipital, parietal and postero-temporal derivations with the maximal current value at 17 Brodmann area. After target stimuli increase of current density in frontal derivations was observed, with the maximal value in the left 9 Brodmann area.

Attention↗
PubMed1999

High resolution study of sleep spindles.

OBJECTIVE: Universal high-resolution time-frequency parameterization of sleep EEG structures. METHODS: A new algorithm called Matching Pursuit was used for the decomposition of sleep EEG into waveforms chosen from a large and redundant set of functions. As a result all signal structures were parameterized in terms of their frequency, time occurrence, time span and energy. Slow wave activity and sleep spindles were identified according to neurophysiological criteria and various distributions describing their time evolution, topographical and frequency characteristics were constructed. RESULTS: Two types of sleep spindles of different topological and spectral properties were identified. High time-frequency resolution made possible separation of superimposed spindles. Cross-correlation between high- and low-frequency components of superimposed spindles revealed a fixed time-delay between them, the high-frequency component preceding the low-frequency one. CONCLUSION: The results of our study suggest that processes of generation of both types of sleep spindles are weakly coupled.

Adult↗
PubMed1996

Assessment of diazepam loading dose therapy of delirium tremens.

The efficacy of the diazepam loading dose method of treatment of delirium tremens was assessed in comparison with the traditional therapy. The experimental group and the control group comprised 51 and 45 patients respectively. The clinical institute withdrawal assessment for alcohol (CIWA-A) scale was applied to assess the intensity of the symptoms. Diazepam doses in the experimental group oscillated from 40 to 210 mg (mean 86.9 +/- 47.2 mg). The control group was receiving diazepam and other psychotropic drugs in divided doses. In the experimental group deliric symptoms were present from 2 to 24 h (mean 6.9 +/- 4.8 h), and in the control group from 2 to 123 h (mean 33.8 +/- 25.7 h). The results show a large efficacy of the loading dose method corresponding to substantial reduction of the psychosis duration (fivefold in comparison to the control group). The method proved to be safe, with no significant complications.

Adult↗
PubMed1996

Analysis of complexity of EEG during sleep.

New multichannel descriptors of EEG activity: complexity (omega), total power (zeta) and generalized frequency (phi) were applied to whole night sleep analysis in 11 healthy subjects. The values of omega and phi decreased systematically from waking to slow wave sleep, and increased systematically in consecutive NREM-REM sleep cycles. The changes of zeta were opposite to omega and phi. These descriptors may be an alternative approach to the EEG sleep analysis.

Adult↗
PubMed1996

Interhemispheric differences of sleep EEG complexity.

Complexity of EEG (omega), a global measure reflecting degree of spatial synchronization, was computed for whole night recordings of sleep EEG of 10 healthy volunteers, 9 males and 1 female (age 21-53) and 6 depressive patients, 5 males and 1 female (age 23-64). Sleep was scored visually in 20 s epochs, omega was calculated in 2.5 s segments and the median from 8 segments (20 s) was calculated. omega was calculated for the whole field of 21 electrodes and for the left and right hemisphere separately (2 x 8 electrodes). Measure of global power (sigma) and generalized frequency (phi) were also computed for the same data. In healthy subjects the complexity was higher over the right hemisphere during waking, and the difference shifted to higher complexity over the left hemisphere in slow wave sleep (F = 5.15, df1 = 4, df2 = 6856, P < 0.0005). The opposite trend was found in depressives (F = 10.51, df1 = 4, df2 = 3960, P < 0.0001).

Adult↗
PubMed1995

Investigation of coherence structure and EEG activity propagation during sleep.

Overnight sleep EEG recorded from 21 derivations was studied for 7 subjects (4 normal and 3 depressive). The multichannel autoregressive model was fitted to all 21 channels simultaneously. Ordinary, multiple and partial coherencies and directed transfer function were estimated for sleep stages and wakefulness. Ordinary coherencies give rather trivial information that coherence decreases with the distance. Partial coherencies revealed specific structure to a large degree repeatable for studied subjects. Study of directed transfer function made possible the identification of main centres from which EEG activity is spreading during sleep. An EEG analysis, based on treating signals as a realization of one process and on simultaneous (not pair-wise) evaluation of time series, offers new possibilities in the investigation of synchronization and functional relations in brains.

Adult↗
PubMed1983

Brain stem auditory evoked potentials and personality.

The investigations involved 20 schizophrenic male patients and 50 healthy male controls. Only those who had good brain stem auditory evoked potentials (BAEP) replicability and clearly visible components were accepted. BAEP were recorded ipsilaterally and contralaterally to the click rarefaction stimuli. Two averagings of 2048 repetitions were superimposed. All the subjects whose BAEP were accepted completed the Eysenck Personality Questionnaire (EPQ). A positive correlation between the P dimension of personality and I-II interpeak conduction time was found in both groups. The correlation of the P score with BAEP latencies increased rapidly from I to II ipsilateral and III contralateral components and then gradually decreased with successive components.

Adult↗
PubMed1982

Vector analysis of auditory evoked potential in the brain stem.

The planar vectocardiographic method was applied to auditory evoked potential in the brain stem (BAEP). It was assumed that the derivations CZ, A1 and A2 from an Einthoven triangle. BAEP were averaged simultaneously on three channels. It was assumed that if CZ were linked to A1 = lead I, CZ to A2 = II and A1 to A2 = III, then I + III = III - II = 0 according to the Einthoven rule. Calculations performed in the averager memory confirmed this hypothesis. The planar vectocardiography method was then applied to BAEP with success. Its advantages are high reliability and amenability to computer analysis.

Brain Stem↗
PubMed1979

Visual evoked response modified recovery cycle and personality dimensions in healthy and schizophrenic subjects.

The aim of this study was to compare the results of the VER recovery cycle as modified by Shagass, in correlation with Eysenck's PEN personality questionnaire scores, in 41 schizophrenic inpatients and 41 healthy subjects. All the subjects were male. In the patient group, a lack of R2 response amplitude facilitation was found. In normals with a high score on the neuroticism scale, less facilitation was found in comparison with the group with low scores in the scale. In the schizophrenic group, the R2 latency did not change with increased S1 stimulus intensity, but in the group of normals the R2 latency increased. The schizophrenic group got higher scores on the scales of psychoticism and neuroticism and lower scores on the extroversion scale. Differences between groups on the psychoticism scale were not significant. A small but significant negative correlation was found between the psychoticism score and facilitation of R2 amplitude in the group of normals. This correlation was greater in the group with low neuroticism.

Adolescent↗
PubMedDate not supplied

[Psychophysiological correlates of primary insomnia].

Psychophysiological differences between 16 patients with primary insomnia, 7 men and 9 women, of mean age 40.8 years, and 16 controls, matched according to age, sex and education, were studied. Insomniacs differed from controls in the following results: their motor activity level was higher during night, sleep efficiency was lower and complexity in slow wave sleep was higher. The Hyperarousal Scale score was higher in insomniacs and it correlated with severity of insomnia in Athens Insomnia Scale. Sleep latency in MSLT was not shorter in patients group. Reaction time was shorter, moreover, the number of presentations necessary to memorize all items of Selective Reminding Test was greater in these patients. Degree of the learning disturbance correlated with the Athens Insomnia Scale score. No correlations were found between Selective Reminding Test and standard polysomnographic parameters. To sum up, the hypothesis on 24-hour hyperarousal in primary insomnia has been confirmed and learning impairment has been documented in the present study, independent of standard polysomnographic parameters.

Adult↗