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P Rappelsberger

Publications and source records attributed to P Rappelsberger.

At least 19 recordsLinked to original sources
PubMed1994

Calculation of event-related coherence--a new method to study short-lasting coupling between brain areas.

This article deals with the estimation of event-related coherence (ERCoh) and its application to the planning and execution of self-paced index finger movement. ERCoh estimation complements the event-related desynchronization (ERD) measurements of rhythms within the alpha band. ERCoh yields information of the functional relationships between different brain areas as a function of time. The time resolution is 125 msec. Before movement onset a contralateral ERCoh increase was found between premotor and motor areas. This coherence increase was accompanied by an ERCoh decrease in parallel to the ERD over the contralateral centro-temporal areas. During movement, the ERD became bilaterally symmetrical. Simultaneously, interhemispheric coherence between contralateral and ipsilateral sensori-motor areas increased.

Brain↗
PubMed1994

Brain and human pain: topographic EEG amplitude and coherence mapping.

Nineteen young healthy volunteers (8 males and 11 females) participated in an experimental ice-cube cold pressor test to study topographic changes of EEG parameters in response to painful stimulation. EEG was recorded with 19 electrodes and quantified by amplitude and coherence analyses. Mean amplitudes and values for local (between adjacent electrodes) and interhemispheric (between electrodes on homologous sites of both hemispheres) coherences were computed for six frequency bands. For the evaluation of changes between EEG at rest (baseline) and EEG during painful stimulation (right or left hand), non-parametric paired Wilcoxon tests were performed. The obtained descriptive error probabilities were presented in probability maps. In the behavioural pain tolerance and subjective pain ratings, no difference in gender or stimulation condition was observed. Under painful stimulation the results showed: (A) most pronounced decrease of Alpha amplitude in the central areas and some increase of high Beta amplitude; (B) increase of local coherence for Alpha and Beta 2 mainly in central regions and centro-frontal leads; and (C) increase of interhemispheric coherence for Alpha and Beta 2 in the central areas. The results of this study indicate clearly that peripheral painful stimulation is reflected by EEG changes. Decrease of EEG amplitude and simultaneous increase of EEG coherence in the central regions can be cortical correlates of human pain.

Adult↗
PubMed1992

Comparative coherence studies in healthy volunteers and Down's syndrome patients from childhood to adult age.

Within the scope of the Munich Pediatric Longitudinal Study, EEG coherence was studied in 212 Down's syndrome patients and 342 healthy controls aged from 6 months up to 30 years. The digitalized EEG records were subjected to spectral analysis. Frequency band-related coherences were calculated to reveal age-specific differences in the functional relationship between two brain areas in Down's syndrome patients and controls. The results show that in the "eyes-open" state the intra-hemispheric coherence in the alpha band was significantly lower (P less than 0.05) in the Down's syndrome patients than in the controls whereas that in the delta bands it was generally higher. The intra-hemispheric coherence in the "eyes-closed" state was generally higher in the Down's syndrome groups than in the controls; however, significant differences could be detected only in some age groups. The age-specific development of coherence in the inter-hemispheric parieto-occipital region was almost identical in Down's syndrome children as in controls, both with open and closed eyes. The most distinct differences were found in the fronto-central inter-hemispheric coherence (P less than 0.01), while the coherence deficiencies in the Down's syndrome group became more prominent with increasing age from school age onwards. These electrophysiological results are compared with the results of neuropathological and neurophysiological studies of other authors. It can be suggested that there are correlations with a significantly small number of dendritic spines in Down's syndrome patients, which was determined in neuropathological examinations. A neuronal model of interpretation is presented which explains the increasing developmental deficit with age in Down's syndrome children.

Adolescent↗
PubMed1992

Thinking with images or thinking with language: a pilot EEG probability mapping study.

This pilot EEG mapping study was designed to explore thinking processes using complex mental imagery and thought processes. EEG was recorded with 19 electrodes (10/20 system against averaged ear lobe signals) while volunteers (n = 42) performed two separate tasks: visualization of an abstract concept and interpretation of a painting. Average spectral parameters such as amplitude, local and interhemispheric coherences were computed for five frequency bands (theta, alpha, beta 1, 2 and 3). Results indicate that the frontal regions are strongly involved during these tasks as evidenced by coherence changes. Changes are also present in temporal, parietal and occipital regions and are discussed in relation to information processing with the frontal regions considering the different cognitive functions required by the tasks.

Adolescent↗
PubMed1991

An approach to a synopsis of EEG parameters, morphology of brain convolutions and mental activities.

A method for the projection of EEG data on the brain surface is proposed. The EEG data are obtained during the performance of mental tasks and represented as probability maps of power and coherence changes with respect to the averaged EEG at rest. The morphological data are obtained from 3D reconstructions of the brain by means of serial slices provided by an MRI scanner. Before scanning the positions of the EEG electrodes were marked by dummy electrodes of plexiglass filled with a contrast medium. Changes of power are color-coded and entered at the respective electrode positions, changes of coherence between the respective positions. The applicability of this procedure in the fields of psychology, psychiatry and neurology is discussed.

Adult↗
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

Effect of lithium on the EEG of healthy males and females. A probability mapping study.

This study is based on 20 healthy volunteers (10 males and 10 females). Between 675 and 1,225 mg lithium carbonate per day was applied for 10 days. EEG was recorded before (day 0) and after lithium intake (day 10) with 19 electrodes and quantified by spectrum analyses. Absolute power and coherence values, between adjacent electrodes and between electrodes on homologous sites of both hemispheres, were computed for five frequency bands. For the evaluation of differences of the EEG parameters obtained on days 0 and 10, a nonparametric paired permutation test was applied. The obtained descriptive error probabilities were presented in topographic maps. Under lithium, the absolute power increased in the entire frequency range, but most distinct in the theta and beta 1 band. The local coherence analyses revealed a clear lateralization: increase in the left hemisphere and decrease in the right. The interhemispheric coherence decreased occipitally and frontally. A comparison of the EEG changes under lithium in males and females showed clear differences in the topographic distribution of power as well as coherence changes.

Adult↗
PubMed1988

Probability mapping: power and coherence analyses of cognitive processes.

In recent years different mapping techniques have proved to be an efficient means in studying cognitive processes. Our approach is based on recordings with 19 EEG channels and the computation of spectral parameters. Power and coherence values are obtained from the EEG of control recordings and recordings during the performance of cognitive tasks and are compared for significant differences. The statistical procedures used yield descriptive error probabilities for the rejection of the null hypothesis which are mapped either colour coded or by black and white squares. The usefulness of this method is demonstrated on a mental cube rotation study involving 31 students, 13 males and 18 females. One essential result during the performance of this test is an increase of theta power only in females. As far as local coherence and the theta band are concerned, males show increased values right parietally and right temporo-occipitally; opposed to this, in females the left hemisphere is more affected. In the beta bands, local coherence increases in males right parietally and left temporo-occipitally. Contrary to this, in females the parietal increase of local coherence is more accentuated in the left hemisphere but temporo- occipital coherence is increased in the right hemisphere. In both sexes interhemispheric parietal coherence increases during cube rotation suggesting increased functional couplings between the hemispheres. This study demonstrates that the inclusion of the coherence parameter in brain mapping furthers the detection of sex and hemispheric differences during the performance of cognitive tasks.

Adult↗
PubMed1986

[Analysis of the extension of epileptic discharges in the animal model].

The study was aimed at the enlightenment of intracortical spreading mechanisms in focal epileptic seizures produced by local application of Acetylcholine. Experiments were made in rabbits. Epi- and intracortical seizure potentials were recorded simultaneously with special electrodes. The recorded signals were analysed using computer aided methods. The results show, that the spreading of the pathological events does not take place continuously but by successive generation of "active zones" independent of the original focus produced by Acetylcholine. In the epicortical recordings, the development of a new focus is indicated by a functional uncoupling between the superficial layers of the cortical area to be involved and the momentary active focus. This functional uncoupling is due to an activation of the middle cortical layers of this area by the focus. As a first sign, high frequent potentials can be observed in the middle cortical layers accompanied by an amplitude decrease in the superficial layers. In the further development high negative discharges appear in the middle cortical layers which lead to characteristic surface positive potentials. This phase indicates that a new focus has developed, i.e. the discharges are no longer triggered by the previous focus. These processes continue as long as inactive cortical areas are available. From the obtained results it can be assumed with high probability that in contrast to previous assumptions the generation of a new epileptic focus is not initiated via superficial axon collaterals but that other cortical connections must be responsible. Additionally, it has to be taken into account that extra- and/or intracellular changes of ion concentrations as a consequence of the massive synaptic bombardment may be responsible for the independent discharges in the focus.

Acetylcholine↗
PubMed1985

On-going EEG in depression: a topographic spectral analytical pilot study.

Spontaneous EEG activities recorded with 19 electrodes (10-20 system) on the scalp were quantified by spectral analytical methods (power and coherence spectra) to reveal changes of power and coherence during different conditions (eyes closed/relaxed, eyes opened/relaxed, flicker stimulation, reading, listening to a story). Control subjects and depressive patients were compared. Power as well as coherence changes were found in all frequency bands. Changes in the organization of the EEG were found in different areas of both hemispheres. The EEG organization was different in control subjects and depressive patients, indicating different levels of vigilance and/or different cognitive strategies in verbal tasks in the two groups.

Adult↗
PubMed1985

Depth profiles of hippocampal rhythmic slow activity ('theta rhythm') depend on behaviour.

Wave shape patterns and spectral properties of hippocampal slow wave activity (RSA) were studied in behaving rats equipped with stationary recording/stimulating electrodes and a movable microelectrode. RSA waves had maximum power at about the hippocampal fissure, and two minima just below the pyramidal cells of CA1 and the inner molecular layer of the dentate gyrus, respectively. The phase profile of RSA was gradual during both running and lever pressing, but the two profiles showed phase differences in the stratum radiatum of CA1 and the hilus. Averaged RSA waves consisted of fast rising and slow decaying components, giving a saw-tooth like pattern. RSA waves were more asymmetric during running than during lever pressing. The slow component showed a sudden polarity reversal below the pyramidal layer of CA1. The fast component of RSA showed a gradual shift and change of the slope with depth. An additional small amplitude wave riding on the slow component ('notch') was present during running. The amplitude increase of the 'notch' occasionally caused frequency doubling of RSA and consequent high power of the second harmonic. The gradual shift and change of the fast component are explained by the hypothesis that somatic inhibitory and dendritic excitatory RSA dipoles in CA1 and dentate gyrus are active at different times of the RSA cycle.

Animals↗
PubMed1985

[Music perception, EEG and musical training].

Changes of EEG during listening to music were studied in two groups of probands, one of them with several years of training on a musical instrument. The EEG was recorded simultaneously from 19 electrodes (10:20 system) against connected ear lobe electrodes. One minute recording periods at rest before and after music were compared with a period of one minute recording during listening to music. 30 seconds of each of these recordings were studied by Fourier analysis. Averaged power and coherence spectra (between transversally adjacent electrodes and between electrodes on homologous regions of both hemispheres) were computed. Broad band parameters were chosen for 5 frequency bands between 4 and 32 Hz. Significant changes of the parameters were represented topographically. During listening to music, a significant reversible decrease of the parameters studied was found: in the musically trained group on both sides, but preponderantly on the right hemisphere, in the non-trained group almost exclusively on the left hemisphere. Moreover, in the trained group, the changes occurred more frequently and involved larger regions of the skull than in the untrained group. In addition, the first group had most changes in the frequency range between 18 and 24 Hz, the second group between 13 and 18 Hz. Finally, comparisons of the changes between the control period before music and music and those between the control period after music and listening to music led to additional conclusions on different strategies of the processing of musical information in musically trained and untrained persons.

Adult↗
PubMed1984

Penicillin-induced epileptic phenomena in the rabbit's neocortex I. The development of interictal spikes after epicortical application of penicillin.

In an attempt to elucidate the generation mechanisms underlying interictal spikes in the neocortex, the temporal development of spikes after the epicortical penicillin (PNC) application was studied. Field potentials (FP) were recorded simultaneously within the 6 neocortical layers with a multielectrode consisting of 16 contacts (10 X 10 micron 2) in a row at spacings of 150 micron. A one-dimensional current-source-density (CSD) analysis yielded the positions of current, sink and source densities, so that the different electrical events during a spike could be more accurately located within the different neocortical layers. After the epicortical application of PNC a typical succession of events, which underly the development of spikes, was observed. These events are similar in the visual and the motor cortex: immediately after the epicortical PNC application negative transients occur in the two uppermost cortical layers as well as within layers V to III. Due to the diffusion of the drug a characteristic succession of different processes takes place. Fully developed spikes show a typical configuration of sources and sinks, a moderate sink in layer V initiates a massive, double-peaked sink within layers II, III. This configuration of sinks suggests that some sort of triggering mechanism takes place. Since similar events are observed during interictal spikes in the visual and the motor cortex, neuronal structures common to both cortical areas are supposed to be responsible for the generation of PNC spikes.

Animals↗
PubMed1984

Penicillin-induced epileptic phenomena in the rabbit's neocortex II. Laminar specific generation of interictal spikes after the application of penicillin to different cortical depths.

To elucidate the generation mechanisms of interictal spikes we analyzed the electrical events in the different layers of the rabbit's neocortex after application of penicillin to distinct cortical layers. Field potentials (FP) recorded simultaneously from all layers with a 16-fold micro-electrode-assembly were subjected to current-source-density analysis (CSD), which allows a more accurate description of local electrical events. To demonstrate the influence of neocortical architectonics on the generation of interictal spikes, 3 different areas-area occipitalis 1, precentralis 1 and 2, according to Fleischhauer et al., were studied. Interictal spikes develop regardless of the depth of PNC application. Moreover the appearance of spikes does not seem to depend exclusively on the diffusion of PNC into a distinct cortical layer (i.e. layers IV and V). The CSD analysis indicated that different generation mechanisms within the different cortical layers underly the spikes. According to CSD configurations maximum sinks occur at depths where the dendrites join closely to form bundles. This finding supports the importance of dendrites for the generation of interictal spikes. Finally, the distribution of CSD patterns is similar in all 3 neocortical areas studied, if PNC is applied to the same cortical depth.

Animals↗
PubMed1984

Computer-assisted EEG topography as a tool in the evaluation of actions of psychoactive drugs in patients.

This paper summarizes a tentative application of EEG topography to the evaluation of the efficiency of psychoactive drugs. It shows that the spectral content of the EEG, recorded simultaneously at different locations according to the international 10-20 system, is a sensitive measure for the quantification of drug activity. Furthermore, coherence analysis reveals differences in the functional organization of the neocortex under neuroleptic drug therapy.

Antipsychotic Agents↗