Search PubMed⌕ Search

Biomedical subjects

U Hegerl

Publications and source records attributed to U Hegerl.

At least 109 records · Page 6Linked to original sources
PubMed1995

Schizophrenics with small P300: a subgroup with a neurodevelopmental disturbance and a high risk for tardive dyskinesia?

Schizophrenics with a neurodevelopmental disturbance resulting in micro- and macroanatomical cortical abnormalities are supposed to form a subgroup clinically characterized by low premorbid adjustment, early onset, incomplete remission, poor outcome, male predominance and high risk for tardive dyskinesia. A small amplitude of the event-related P3 (P300) potential could be a marker of this subgroup, because the cortical neurons and their orderly laminar arrangement are crucial for the electrogenesis of P3. In a 2-year follow-up study, auditory evoked P3 was recorded in 89 stabilized schizophrenic outpatients. Patients who developed tardive dyskinesia during the follow-up had smaller P3 than matched controls. Furthermore, a small P3 was associated with low premorbid adjustment, pronounced residual symptoms, low relapse rate, and male predominance. These findings indicate that schizophrenic patients with a reduced P3 have a higher risk of developing tardive dyskinesia and correspond clinically to a schizophrenic subgroup with a supposedly neurodevelopmental disturbance.

Adult↗
PubMed1994

Ventricle size and P300 in schizophrenia.

Both ventricular enlargement and reduced P3 amplitudes are consistent findings in schizophrenic patients, suggesting that the two measures reflect a common underlying pathophysiological process in schizophrenia. Investigating 14 stabilized schizophrenic outpatients, a relationship between the size of the lateral ventricles as well as of the third ventricle on CT scans and the auditory event-related P3 amplitude was, however, not found. This negative result suggests that ventricular enlargement and reduced P3 amplitudes in schizophrenics reflect different pathophysiological processes. It is assumed that the P3 amplitude is related rather to abnormalities in the temporal lobe of schizophrenic patients.

Adult↗
PubMed1994

Intensity dependence of auditory evoked dipole source activity.

The spatio-temporal approach of dipole source analysis represents a crucial methodological progress in research on individual differences in the dependence of auditory evoked potential amplitude on stimulus intensity (augmenting/reducing) because overlapping subcomponents of the N1/P2-component can be separated and can be related to their generating cortical structures. Basic aspects of the intensity dependence of auditory evoked dipole source activity were analysed in 40 healthy subjects. The evoked responses to binaural 1000-Hz tones at five levels of intensity (60, 70, 80, 90, 100 dB sound pressure level) were recorded at 33 sites across the scalp. The dipole source analysis of the grand average data confirms the reports in the literature that the N1/P2 potentials at the scalp can be explained by two dipoles per hemisphere: a tangential dipole, representing activity of the superior temporal cortex (including primary auditory cortex), and a radial dipole, representing activity of the lateral temporal cortex (secondary auditory areas). The intensity dependence of the tangential dipole activity was significantly more pronounced than that of the radial dipoles, supporting the assumption that radial and tangential dipoles represent different physiological processes. A high reliability of the intensity dependence of the tangential dipole (Pearson correlation: r = 0.88) was found when retesting the subjects after three weeks. Age was negatively correlated with the intensity dependence of the tangential dipole. Dipole source analysis proved to be a reliable method which allows, at least in part, to study separately the intensity dependence of the evoked responses from primary and secondary auditory cortices. This is of importance with regard to the hypothesis that the central serotonergic system modulates the intensity dependence of the evoked N1/P2-response of primary auditory cortex.

Adult↗
PubMed1994

Dipole source analysis. Linking scalp potentials to their generating neuronal structures.

The spatiotemporal approach of dipole source analysis is a crucial methodological advance in event-related potential research, as overlapping subcomponents of cortical evoked potentials can be separated and related to their generating structures. This enhances the reliability and validity of event-related potential parameters and facilitates the link to underlying neurochemical processes. The present paper presents methodological aspects of the dipole source analysis of auditory-evoked potentials to different stimulus intensities.

Adult↗
PubMed1994

Auditory evoked dipole source activity: indicator of central serotonergic dysfunction in psychiatric patients?

Event-related potentials reflect postsynaptic effects of cortical neurotransmitters and may be useful as indicators of the function of neurochemical systems. Arguments are presented for the hypothesis that the stimulus-intensity dependence of the auditory-evoked N1/P2 component may be a noninvasive indicator of behaviorally relevant aspects of central serotonergic activity. Converging evidence from our own studies as well as from the literature suggest that a pronounced intensity dependence of this component reflects low central serotonergic neurotransmission and vice versa. Dipole source analysis represents an important methodological advance in this context, because N1/P2 subcomponents generated by different cortical structures with different serotonergic innervation can be separated.

Auditory Cortex↗
PubMed1994

Auditory-evoked dipole source activity as indicator of withdrawal severity in alcoholic patients.

The relationship between auditory-evoked potentials and the ethanol withdrawal syndrome was investigated in alcoholic inpatients using dipole source analysis. It was found that the increase in N1/P2 amplitude during withdrawal was positively correlated to the general severity of the withdrawal, but not to single symptoms such as seizures. Monitoring of initial changes in the auditory-evoked N1/P2 amplitude may be of predictive value concerning the withdrawal severity of alcoholic patients.

Adult↗
PubMed1994

Evoked potentials, serotonin, and suicidality.

The link between suicidality and serotonergic dysfunction is a consistent finding in biological psychiatry. In three independent studies we found weak intensity dependence of auditory evoked potentials, which may be related to high serotonergic activity, in psychiatric patients with a history of suicide attempts. This result seems to contradict studies reporting low serotonergic activity in acute suicidal patients. As an explanation for this discrepancy we propose that serotonergic activity may be low only in acute suicidal states, and that high serotonergic activity, as reflected by a weak intensity dependence, may characterize high-risk patients, in whom a transient decrease of serotonergic activity is accompanied by acute suicidality.

Alcoholism↗
PubMed1993

Intensity dependence of auditory evoked potentials as an indicator of central serotonergic neurotransmission: a new hypothesis.

Because of the increasing importance of the central serotonergic neurotransmission for pathogenetic concepts and its role as a target of pharmacotherapeutic interventions in psychiatry, reliable indicators of this system are needed. It is proposed that the stimulus intensity dependence of auditory evoked N1/P2-component, which is probably modulated by cortical serotonergic innervation, may be a useful and noninvasive indicator of behaviorally relevant aspects of serotonergic activity. Converging evidence from our own studies as well as from the literature suggests that a pronounced intensity dependence of auditory evoked N1/P2-component reflects low central serotonergic neurotransmission. Recent findings concerning general functional aspects of the brain serotonin system reveal that this system is well qualified for adjusting individual levels of sensory processing ("set the tone"), especially in the primary auditory cortex in which the N1/P2-component is mainly generated. Dipole source analysis represents an important methodological advance in this context because it allows the separation of N1/P2-subcomponents generated in the primary auditory cortex from those generated in secondary auditory areas.

Arousal↗
PubMed1992

Intensity dependence of auditory evoked potentials and clinical response to prophylactic lithium medication: a replication study.

A predictor of clinical response to prophylactic lithium treatment in affective psychoses would be of considerable importance. In a pilot study, responders to prophylactic lithium medication, as compared with nonresponders, were characterized by a steeper slope of the amplitude/stimulus-intensity function (ASF slope) of the N1/P2 component of the auditory evoked potential. We tried to replicate this finding in 34 stabilized outpatients with affective illness who had been treated with lithium for at least 3 years. As in the pilot study, responders were again characterized by steeper ASF slopes than nonresponders. Since a steep ASF slope seems to indicate low central serotonergic function, it is speculated that a steep ASF slope characterizes those patients with a serotonin deficit who respond to serotonin agonists like lithium.

Adult↗
PubMed1992

Intensity dependence of auditory evoked N1/P2 component and personality.

The slope of the amplitude/stimulus intensity function (ASF) of sensory evoked potentials was found to be related to 'action-oriented' personality traits like 'sensation seeking', 'extraversion', and 'impulsivity'. We studied the ASF slope of the auditory evoked N1/P2 component as well as short-term ASF slope changes and their relationship to a German personality inventory (Freiburger Persönlichkeits-Inventar) in 33 healthy subjects. The ASF slope correlated negatively with 'life contentment' and positively with 'stress' in the first run. Stronger associations, however, were noted between slope changes within one test session and personality. Subjects scoring high on the second-order factor 'aggressive excitability' were characterized by a slope decrease from the first to the second run, following a 20-min interval. This finding of personality-dependent test-retest changes of the ASF slope stresses the importance of monitoring the duration of the recording when studying ASF slopes and offers an explanation for inconsistencies in the literature concerning cross-modal correlations in visual and auditory ASF slopes. The hypothesis is proposed that the serotonergic system, which has been related to 'action-oriented' personality, is involved in the modulation of the intensity dependence of the auditory evoked N1/P2 component.

Acoustic Stimulation↗
PubMed1990

Effect of lithium on the dynamics of electroencephalographic vigilance in healthy subjects.

Eleven healthy male volunteers had EEG recordings before lithium, after 10 days of lithium administration and 2 weeks after discontinuation of lithium. As postulated from previous investigations the typical lithium effect on the dynamics of electroencephalographic vigilance proved to consist of: (1) a decrease of non-alpha segments, i.e., an increase of alpha continuity or an enhancement of alpha activity; (2) an increase of the anterior/posterior ratio of absolute alpha power (AQ); (3) a decrease of the dynamic variability of this alpha anteriorization (CV-AQ). In addition the decrease of dynamic variability of alpha anteriorization was found to be associated with an increase in the amplitude of P1/N1 components of auditory evoked potentials.

Adult↗
PubMed1990

Expressed emotion and auditory evoked potentials.

The expressed emotion (EE) of key relatives has been shown to predict the course of illness in psychiatric patients. In this study, we examined whether there might be physiological correlates to the EE index in nonbiological key relatives of patients with affective psychoses. High-EE and low-EE relatives were compared concerning their slopes of the amplitude/stimulus intensity function (auditory evoked N1/P2-component). We found that the slopes were clearly steeper in the case of low-EE relatives. In comparing the slopes of all key relatives with those of an age-matched control group without psychiatrically ill partners, we could find no differences. Therefore, the slope differences between high-EE and low-EE relatives do not seem to reflect differences in the illness of partners. We speculated whether a steep slope as well as low EE could be associated with an action-oriented, impulsive communication style, which would prevent the development of an affectively tense communication pattern.

Adult↗
PubMed1990

Event-related potentials and the prediction of differential drug response in psychiatry.

Differences in physiological trait or state characteristics of the organism are ultimately responsible for the wide range of interindividual variability in the clinical response to psychoactive drugs. Event-related potentials (ERPs) appear especially valuable in assessing these physiological characteristics, and might therefore be useful as predictors of the individual drug response. Seven criteria for the selection of potential predictor variables are presented. A review of the literature reveals consistent, prospective and cross-validated results concerning the prediction of the clinical response to psychostimulants in hyperkinetic children. Consistent findings have also been reported concerning the relationship between ERPs and the antidepressive as well as prophylactic effects of lithium. Relating to other aspects of drug therapy in psychiatry, there have been isolated studies describing ERP differences between responders and nonresponders. It is concluded that the use of ERPs in the prediction of differential drug response is a promising research strategy, deserving more attention. Its relevance will be seen not only in its practical value for therapeutic decisions, but also in the clarification of therapeutic mechanisms.

Evoked Potentials↗
PubMed1989

Sensation seeking and auditory evoked potentials.

The relationship between auditory evoked potentials (AEP) and the German version of Zuckerman's Sensation Seeking Scale was examined. The slope of the amplitude/stimulus intensity function (N1/P2 component) and the N1 latency were particularly studied, as these variables have been found to be potential predictors of the response to lithium prophylaxis. Thirty-three healthy subjects participated in two testing series on the first day and in a third run 3 weeks later. Binaural clicks at four intensity levels (58, 68, 78, 88 dB HL, ISI 2.1 sec) were presented in randomized order by headphone. Eighty responses were averaged at each intensity level. The pattern of correlation between the German version of the Sensation Seeking Scale and a personality inventory (FPI) supports the validity of the Sensation Seeking Scale. Only a tendency toward steeper slopes of the amplitude/stimulus intensity function (ASF) in high sensation seekers was observed in the first run. However, there was a significant interaction of sensation seeking and the test run. Only high sensation seekers showed an influence of retesting on the slope of the ASF, leading to a decrease of the slope in the second, compared with the first run. This might correspond to the psychological pattern of sensation seeking, which is characterized by a permanent need for new and exciting situations and, at the same time, by a rapid loss of interest in these situations. With regard to the N1 latency, a significant interaction of sensation seeking and lead was found. Low sensation seekers showed longer N1 latencies over the right than over the left hemisphere, a finding that accords with some psychophysiological theories on the relation between asymmetric hemispherical activation and certain psychological constructs. Our results support the view that sensation seeking is a personality feature that is closely related to certain physiological variables.

Adult↗
PubMed1989

The observing subject and psychophysiological research: an epistemological discourse.

Realizing that scientific knowledge was not based on a simple disclosure of reality, but was rather invented and developed in accordance with our own conceptions and prejudices, it should no longer be possible to consider matters as if they existed independently of us 'out there'. Taking as examples the notions of 'memory' and 'information' we try to elucidate the relevance this perspective has with respect to neuro- and psychophysiological research.

Behavior↗
PubMed1989

[Psychoactive drugs and cortical evoked potentials].

Evoked potentials (EP) are an important research instrument in psychopharmacology. They allow to investigate central nervous processes in a time range of milliseconds. Furthermore, they are useful as a link between the basal biochemical or neuroendocrinological and the psychological levels of description. The literature concerning the relationship between EP and the therapeutically important classes of psychoactive drugs (stimulants, neuroleptics, antidepressants, minor tranquilizers/sedatives, lithium salts, carbamazepine) was reviewed. The following two questions were treated separately: 1. What are the effects of psychoactive drugs on EP in healthy subjects and in patients? 2. Are EP suitable as predictors of the clinical response to psychopharmacological treatment? It was found that most effects of psychoactive drugs on the EP are not specific for one class of agents. Furthermore these effects depend on factors concerning the subject (e.g. age, gender, diagnosis, symptomatology, personality, initial value of the EP-variable), the treatment (e.g. dosage, duration), or the context and procedure of the EP recording. Therefore, the importance of evoked potentials for the classification of new psychoactive drugs has been limited until now. However, the EP research has stimulated the development of mostly psychological concepts about the way of action of some psychoactive drugs. The use EP as predictors of the response to psychopharmacological treatment seems to be promising. There are consistent findings concerning the prediction of the clinical response to stimulants and lithium salts.

Cerebral Cortex↗