Biomedical subjects

M Jobert

Publications and source records attributed to M Jobert.

At least 19 recordsLinked to original sources

PubMed2002

Recording EEG and EP data.

Recording evoked potentials (EPs), electroencephalogram (EEG) signals and polysomnographic biosignals requires particular attention with respect to amplification, filtering, and data handling. The present paper is aimed at providing a short overview of the fundamentals on recording techniques and the basics on biosignal processing methods used in EEG studies. It also examines the aspects associated with the reproducibility of EEG measurements, as well as the recording duration by Pharmaco-EEG (PEEG) studies.

Electroencephalography↗

PubMed2001

Changes in quantitatively assessed tremor during treatment of major depression with lithium augmented by paroxetine or amitriptyline.

Tremor is a relatively frequent side effect of lithium and of antidepressants with serotonergic properties. It can be expected that combinations of lithium (which is itself serotonergic) with such antidepressants will enhance not only efficacy, but also the incidence of side effects, including tremor. To quantitatively monitor the effect of antidepressant augmentation of ongoing lithium therapy on tremor, lithium-maintained patients with a breakthrough episode of major depression were randomly assigned under double-blind conditions to receive paroxetine 20 mg/day (N = 14) or amitriptyline 75 mg/day (N = 17). The initial dosages could be increased after 2 weeks to 40 mg/day and 150 mg/day, respectively, and the patients were treated for 6 weeks. Tremor activity was assessed weekly, quantitatively by accelerometry and qualitatively with the Dosage Record and Treatment Emergent Symptom Scale. Statistical analysis detected no significant difference between the treatment groups with respect to changes in mean tremor activity relative to baseline. However, analysis of the pooled data showed that tremor increased significantly during the course of combined lithium and antidepressant therapy, with the greatest increments occurring independent of dosage approximately 3 weeks after initiation of combination treatment. Although the mean tremor activity subsided toward the end of treatment, tremor activity on the whole was still significantly greater after 6 weeks of combined lithium and antidepressant treatment than at the start of combination therapy. Increased tremor was not associated with decreased medication compliance, and no patient discontinued treatment because of increased tremor. Tremor frequency was not affected by the study treatments.

Adult↗

PubMed1999

Effect of two antidepressant drugs on REM sleep and EMG activity during sleep.

In a placebo-controlled study, the effects on sleep of single and repeated doses of imipramine and dexnafenodone, an antidepressant drug under development, were investigated in young, healthy volunteers. In contrast to placebo, both drugs suppressed REM sleep substantially after acute and repeated administration. As a consequence, REM sleep latencies increased under active treatment to mean values which were about two to four times larger than baseline values. Since the active inhibition of the muscle tone is a distinct feature of REM sleep, we studied the influence of the two antidepressant drugs on this variable. By means of computerised EMG analysis, tonic and transient EMG activity were computed for total recording time and for the different sleep stages. While tonic EMG activity during sleep was increased with both drugs, transient EMG events remained unaffected. Computerised analysis of the microstructure of sleep is an effective tool for studying the effect of antidepressant drugs on sleep.

Adrenergic Uptake Inhibitors↗

PubMed1996

The diurnal distribution of sleep propensity: experimental data about the interaction of the propensities for slow-wave sleep and REM sleep.

The aim of the present study was to assess the diurnal variation of sleep propensity by evaluating the temporal distribution of sleep onset latency (SOL) and REM- and slow-wave sleep (SWS) parameters in systematically scheduled daytime naps for 12 young males. To reduce the effect of prior SWS on subsequent REM sleep, a double-nap technique was used, i.e. two adjacent naps A and B, which were separated by a 10-min break. Nap duration was adjusted in such a way that nap A allowed 30 min of sleep and nap B one complete NREM-REM cycle. EEG slow wave activity (SWA, power density from 0.5-4 Hz) was estimated from nap A and REM sleep parameters from nap B. The time span between 08.00 hours and 24.00 hours was covered by nine double-naps at 2 h intervals. The order of the nap sessions was systematically varied within and across subjects. For each subject, the time between successive double-nap recordings was at least three days. SOL was shortest in the time interval 12.00 hours to 16.00 hours and significantly longer between 20.00 hours and 24.00 hours. REM sleep duration and the percentage of sleep onset REM episodes decreased continuously from 08.00 hours to the interval 18.00-20.00 hours and increased thereafter, with a time course inversely related to the one of body temperature, which was also measured continuously. SWA showed a steady, threefold increase from 08.00 hours to 24.00 hours. The study offers new data on the diurnal variation of sleep propensity which seems to be a composite function of the drives for SWS and REM sleep.

Adult↗

PubMed1996

The use of diurnal vigilance changes in the EEG to verify vigilance-enhancing effects of memantine in a clinical pharmacological study.

In elderly subjects there is a vigilance decrease from morning to noon which was used in a clinical pharmacological model as a state condition to verify vigilance-enhancing effects of an antidementia drug. In this model the effects of Memantine (20 mg, single-dose application) on the quantified EEG were investigated in 16 elderly (mean age: 65 +/- 5 years), healthy subjects (10 females, 6 males) in a randomised, twofold cross-over design vs. placebo under double-blind conditions. EEG was recorded before medication, and 2 and 4 h after medication under reaction time (RT) and resting (RS) conditions. EEG data were subjected to spectral analysis and the topographic distribution of the amplitude values was mapped. The results show that a time-dependent decrease (from morning to noon) in vigilance (indicated by an increase in average EEG amplitudes caused by increased synchronisation in the alpha and beta range and an increase in delta) occurred under placebo which was counteracted by Memantine. The diurnal variations of the EEG and their compensation by a pharmacological agent represent an effective model for investigating the vigilance-enhancing effects of antidementia drugs.

Aged↗

PubMed1996

Different modes of data processing and statistical testing applied to the same set of pharmaco-EEG recordings: effects on the evaluation of a selective and reversible MAO A inhibitor (brofaromine).

The comparison of two different modes of data processing and two different approaches to statistical testing both applied to the same set of EEG recordings was the main objective of this pharmacological study. Brofaromine (CGP 11,305 A), a new selective and reversible monoamine oxidase type A inhibitor was used as an example for investigating a potentially antidepressant drug in clinical development. The two modes of pharmaco-EEG (PEEG) data processing differed mainly in the sampling frequency and definition of spectral parameters. Patterns of significant changes were noted in terms of descriptive data analysis using either a nonparametric Wilcoxon signed-rank test or an ANOVA of transformed data, as suggested by Conover and Iman. These data clearly demonstrate that slight discrepancies in the results may simply arise from differences in data processing and statistical approach applied. In spite of these discrepancies, the pattern of brofaromine-induced PEEG changes was very similar regardless of the mode of data handling used.

Adult↗

PubMed1996

Soporific effect of the neurosteroid pregnanolone in relation to the substance's plasma level: a pilot study.

The soporific effect of the neuroactive steroid pregnanolone, a metabolite of progesterone, and its relationship with plasma concentrations was assessed in 18 young, healthy, male volunteers for 2 h after administration of a single dose of pregnanolone prepared in two different formulations. Sedation was measured as sleep propensity and power increase in the low frequency delta band of the quantified EEG, based on 5-min polygraphic (EEG, EOG, EMG) recordings under resting conditions, which were performed immediately before, and 30, 60, 90, and 120 min after intake of the study drug. With both formulations, there was a time-dependent increase in plasma concentration of pregnanolone with highest values 1-2 h postdosing. The model of short polygraphic recordings under resting conditions demonstrated soporific effects of pregnanolone. Compared to predosing baseline the number of sleep attempts and the time asleep increased after treatment with a peak 60 min postdosing. Quantitative EEG analysis revealed an increase of absolute amplitude in the delta frequency range with a comparable temporal pattern. Correlations between the soporific effect and plasma concentrations of pregnanolone suggest that the effects were drug-related, although this has to be replicated with placebo control.

Adult↗

PubMed1996

Processing visual evoked potentials based on matched filtering of single trial responses.

Physiological signals recorded after presentation of a stimulus can be considered as the sum of an evoked sensory response and uncorrelated noise corresponding to the spontaneous neural background activity. In case of low signal-to-noise ratio, the sensory signal is estimated by averaging a large number of single trial records sampled under the same experimental conditions. The averaging technique, however, is inappropriate for displaying trial-to-trial variations that may occur during a recording session. A method based on matched filtering was developed for processing single visual evoked potentials (VEPs). To illustrate the performance of this method, a set of VEPs for grating patches of 8 different contrasts (including 0) was evaluated. The VEPs were subjected to signal detection analysis by computing for each contrast similarity indices between the single trial records and the averaged response used as a template. The signals were analysed in terms of probability density distributions, expressing the goodness of fit between template and each single waveform.

Cluster Analysis↗

PubMed1995

Methodological considerations for the evaluation of EEG mapping data: a practical example based on a placebo/diazepam crossover trial.

Quantitative EEG is a sensitive method for measuring pharmacological effects on the central nervous system. Nowadays, computers enable EEG data to be stored and spectral parameters to be computed for signals obtained from a large number of electrode locations. However, the statistical analysis of such vast amounts of EEG data is complicated due to the limited number of subjects usually involved in pharmacological studies. In the present study, data from a trial aimed at comparing diazepam and placebo were used to investigate different properties of EEG mapping data and to compare different methods of data analysis. Both the topography and the temporal changes of EEG activity were investigated using descriptive data analysis, which is based on an inspection of patterns of pd values (descriptive p values) assessed for all pair-wise tests for differences in time or treatment. An empirical measure (tri-mean) for the computation of group maps is suggested, allowing a better description of group effects with skewed data of small samples size. Finally, both the investigation of maps based on principal component analysis and the notion of distance between maps are discussed and applied to the analysis of the data collected under diazepam treatment, exemplifying the evaluation of pharmacodynamic drug effects.

Adult↗

PubMed1995

ECG activity in the sleep of insomniac patients under the influence of lormetazepam and zopiclone.

The influence of the benzodiazepine hypnotic lormetazepam (1 mg) and the cyclopyrrolone hypnotic zopiclone (7.5 mg) on heart rate activity was studied in 16 elderly insomniacs in a placebo-controlled, randomised, 3-fold crossover trial. After digital preprocessing of the ECG, QRS complexes were automatically recognised by a detection technique based on adaptative thresholds. Both R-R periodicity and heart rate variability were analysed as a function of sleep stages and time of night. Under placebo, heart rate decreased significantly from the first to the second half of the night. The relationship between sleep stages and heart rate remained constant under both hypnotics. Although the two substances significantly modified the distribution of sleep stages, no relevant changes in ECG activity were observed when the proportion of the different sleep stages was taken into consideration.

Aged↗

PubMed1995

On the choice of recording duration in pharmaco-EEG studies.

Quantitative EEG is a sensitive method used to assess the effects of pharmacological substances on the central nervous system (CNS) activity. A standard technique is to measure the EEG under vigilance-controlled and resting conditions for a short duration, for example 5 min. The aim of the present study was to investigate the stability of 5-min EEG recordings. While the time course of the EEG was fairly stable during the recording session under the vigilance-controlled condition, systematic trends became apparent under the resting condition. Pharmaco-sensitivity of the EEG and its reliability increased with the recording duration. Five minutes of EEG recording seem to be sufficient and well chosen to evaluate the influence of drugs on the EEG.

Adult↗

PubMed1994

Automatic analysis of sleep using two parameters based on principal component analysis of electroencephalography spectral data.

A computer program for the analysis of a sleep electroencephalogram (EEG) is presented. The method relies on two steps. First, a spectral analysis is performed for signals recorded from one or more electrode locations. Then, two EEG parameters are obtained by storing the spectral activity in a multidimensional space, whose dimension is reduced using principal component analysis (PCA) techniques. The main advantage of these parameters is in describing the process of sleep on a continuous scale as a function of time. Validation of the method was performed with the data collected from 16 subjects (8 young volunteers and 8 elderly insomniacs). Results showed that the parameters correlate highly with the hypnograms established by conventional visual scoring. This signal parametrisation, however, offers more information regarding the time course of sleep, since small variations within individual sleep stages as well as smooth transitions between stages are assessed. Finally, the concurrent use of both parameters provides an original way of considering sleep as a dynamic process evolving cyclically in a single plane.

Adult↗

PubMed1994

Wavelets-a new tool in sleep biosignal analysis.

The wavelet transform is a relatively new approach to data processing which has been applied in different areas such as signal, speech and image processing. In the last decade, many papers have been published on wavelet theory and its applications. The wavelet transform provides an elegant alternative to the classical Fourier or Gabor transforms unifying numerous signal processing techniques in a common framework. The purpose of the present paper is to provide an overview of the applicability of the wavelet transform to EEG signal analysis. In the first part of the paper the mathematical background is summarized. In the second part, applications to the sleep EEG field are presented and discussed. The results of these illustrations demonstrate the usefulness of the wavelet transform to solve various problems including signal parametrization, pattern recognition and biosignal representation.

Journal Article↗

PubMed1994

Effects of hypericum extract on the sleep EEG in older volunteers.

The effects of treatment with high doses (300 mg three times daily) of hypericum extract LI 160 on sleep quality and well-being were investigated over a 4-week period. The double-blind, placebo-controlled study was conducted with 12 older, healthy volunteers in a cross-over design, which included a 2-week wash-out phase between both treatment phases. A hypostatic influence of the REM sleep phases, which is typical for tricyclic antidepressants and MAO inhibitors, could not be shown for this phytopharmacon. Instead, LI 160 induced an increase of deep sleep during the total sleeping period. This could be shown consistently in the visual analysis of the sleeping phases 3 and 4, as well as in the automatic analysis of slow-wave EEG activities. The continuity of sleep was not improved by LI 160; this was also the case for the onset of the sleep, the intermittent wake-up phases, and total sleep duration.

Anthracenes↗

PubMed1994

A computerized method for detecting episodes of wakefulness during sleep based on the alpha slow-wave index (ASI).

A method for the automatic detection of episodes of wakefulness during sleep is presented. The algorithm is based on the evaluation of the alpha slow-wave index (ASI), a measure that has been developed to detect fluctuations of vigilance in daytime pharmaco-electroencephalogram studies. Its application to sleep data was validated with polysomnographic recordings from 16 elderly insomniacs and 16 young healthy subjects. The rate of agreement between the computerized procedure and the visual scoring of wakefulness was 94.0% for the insomniacs and 96.9% for the healthy subjects. The decision criterion used by the computer allowed the definition of a subject-adapted threshold for the detection of wake episodes. The method opens new perspectives for the automatic analysis of continuous 24-hour sleep-wake recordings.

Aged↗

PubMed1993

A comparison between visual and computer assessment of sleep onset latency and their application in a pharmacological sleep study.

Sleep onset latency (SOL) is frequently defined as the time between lights-out and the first epoch of sleep stage 2. In practice, SOL can be quantified easily on the basis of visual examination. We have developed a computer algorithm allowing an automatic estimation of this parameter. The agreement between both strategies, visual and computer analysis, was tested using data from a pharmacological sleep study with 16 elderly insomniacs, which was aimed at comparing the effects of lormetazepam and zopiclone on polysomnography. A high correlation was found between the visual and the computer-based determination of SOL. Drug-related differences in SOL could be shown with both approaches.

Aged↗

PubMed1992

Pattern recognition by matched filtering: an analysis of sleep spindle and K-complex density under the influence of lormetazepam and zopiclone.

The evaluation of sleep EEG patterns is mostly accomplished by visual analysis. With modern personal computers however, it is possible to perform signal detection within a reasonable length of time automatically. This paper presents a method for signal processing based on matched filtering. This allows the detection of sleep spindles and K-complexes in a sleep EEG recording with a high degree of accuracy. First the technique is described, and the results of a validation study based on the comparison of visual evaluations and computer analysis are presented. Thereafter, results of an application study are presented. Sleep spindle and K-complex density under the influence of lormetazepam and zopiclone were examined. Under both medications sleep spindle density increased while K-complex density decreased. Computation of Pearson's correlation coefficients demonstrated that the interindividual sleep spindle and K-complex variations under both treatments are highly correlated. The data suggest that lormetazepam and zopiclone, although chemically different, have a similar mode of action and display comparable effects on the sleep EEG.

Adult↗

PubMed1992

Topographical analysis of sleep spindle activity.

There is evidence for two types of sleep spindle activity, one with a frequency of about 12 cycles/s (cps) and the other of about 14 cps. Visual examination indicates that both spindle types occur independently, whereby the 12-cps spindles are more pronounced in the frontal and the 14-cps spindles in the parietal region. The purpose of this paper is to provide more information about the exact topography of these patterns. First the occurrence of distinct signals in anterior and posterior brain regions was verified using pattern recognition techniques based on matched filtering. Thus the existence of two distinct sources of activity located in the frontal and parietal region of the brain, respectively, was demonstrated using EEG frequency mapping. Evaluation of sleep recordings showed high stability both in the frequency and location of the presumed spindle generators across sleep. Pharmacological effects of lormetazepam and zopiclone on both spindle types were investigated. Both substances enhanced the sleep spindle activity recorded from the frontal and parietal electrodes, but this increase was more pronounced in the parietal brain region.

Adult↗