Biomedical subjects

G Juckel

Publications and source records attributed to G Juckel.

At least 37 records · Page 2Linked to original sources

PubMed2001

The effect of the skull on event-related P300.

OBJECTIVES: Event-related potentials (EP) indicate neuronal processes with a high temporal resolution, while functional magnetic resonance imaging (fMRI) has a high spatial distribution. Information from both techniques may complement each other. However, this combination is fraught with difficulty because of a possible interference of the skull or the scalp with scalp-recorded EP. The aim of the present study was to investigate this influence of skull and scalp thicknesses on event-related P300 potentials. METHODS: Thirty healthy controls were examined using an auditory evoked P300 elicited by a standard oddball paradigm. Skull and scalp thicknesses were determined using coronal T2-weighted magnetic resonance imaging (MRI). RESULTS: P3b-amplitudes were significantly correlated with temporo-parietal skull thickness (r=-0.42; P=0.021; regression slope of -1.14 microV/mm skull thickness), whereas scalp had no influence on P300. The amplitude of the more frontal subcomponent P3a was not related to frontal skull thickness. CONCLUSIONS: Therefore, the utility of P300 as a research tool can be enhanced when adjustment for skull thickness is made.

Adult↗

PubMed2001

[Recurrence of paranoid hallucinatory psychoses after beginning a fasting period in a patient with anorexia nervosa].

We report the case of a 37-year old female patient with anorexia nervosa. For many years, this patient fasted for various periods, from days to weeks, in order to reduce her body weight and to achieve an euphoric effect. In the course of the past four years she developed acute paranoid-hallucinatory psychosis immediately following one week episodes of fasting, requiring psychiatric in-patient treatment three times. Psychotic prodromal symptoms could not be elicited before nor at the beginning of fasting periods, pointing towards a caustic relationship between the fasting and the psychotic decompensation. Based on this case, we discuss the hypothesis that the fasting in anorexia nervosa leads to acute hyperactivity of the dopaminergic system which could explain the development of paranoid-hallucinatory psychosis. This case exemplifies that vulnerable patients with a similar history should strongly be advised to avoid fasting and other dietetic methods. Explanation of the enhanced risk to develop psychosis could be of therapeutic use for treating the anorexia nervosa in such patients.

Adult↗

PubMed2001

Kinematic analysis of handwriting movements in patients with obsessive-compulsive disorder.

OBJECTIVES: Basal ganglia dysfunction is supposed to play a part in the pathophysiology of obsessive-compulsive disorder (OCD). A new computer aided technique for the analysis of hand movements, allowing the detection of subtle motor performance abnormalities, was applied in this study of patients with OCD and healthy controls. METHODS: Using a digitising graphic tablet, hand motor performance was studied in 22 unmedicated patients with OCD and compared with 22 healthy controls. All subjects drew superimposed concentric circles with both the right and the left hand, in addition to writing a given sentence, their personal signature, and letter sequences in four different sizes. Kinematic parameters were calculated to quantify hand motion. RESULTS: Patients with OCD had significant impairments of handwriting performance, reflected by lower peak velocity (sentence t=3.6; p=0.001; signature t=2.8; p=0.01) and micrographia (sentence t=3.4; p=0.002; signature t=2.5; p=0.02), compared with controls and shortened acceleration phases per stroke (sentence t=2.4; p=0.02; signature t=4.1; p=0.000). By contrast, in repetitive drawing, patients with OCD had higher peak velocity than healthy controls (group x task interaction p<0.01). There were no significant differences in left and right hand performance between groups. Patients with early versus late age of onset differed in handwriting parameters, such as handwriting consistency. Greater severity of obsessions and compulsions correlated with increasingly poor handwriting performance in patients with OCD. CONCLUSIONS: A subtle motor dysfunction in OCD can be detected with a digitising tablet. The findings show handwriting impairments in patients with OCD, in line with the assumption that basal ganglia dysfunction is part of OCD pathophysiology. Repetitive motor pattern performance was not impaired, but rather tended to be even better in patients with OCD than in controls. The findings also support the concept that patients with OCD with early versus late age of onset differ in pathophysiological mechanisms and basal ganglia dysfunction.

Adolescent↗

PubMed2001

Prefrontal cortex modulation of mood and emotionally induced facial expressions: a transcranial magnetic stimulation study.

Repetitive transcranial magnetic stimulation (rTMS) can serve as a tool to experimentally test hypotheses of prefrontal cortex (PFC) modulation of emotions. The present study used rTMS to test whether self-rated mood and emotionally induced facial expressions are hemispherically lateralized depending on their valence, as indicated by previous studies. Healthy volunteers underwent mood self-rating and computerized analysis of emotionally induced facial expressions before and after rTMS of left or right PFC. Facial expression analysis revealed lateralized changes of facial expressions after rTMS, whereas changes of subjective mood ratings did not show a hemispheric lateralization. On the basis of this study, the authors propose to combine rTMS and facial expression analysis for further studies of the cortical modulation of emotions in humans.

Adult↗

PubMed2000

Loudness dependence of auditory evoked potentials in obsessive-compulsive disorder: a pilot study.

In recent years it has been suggested that a serotonergic dysfunction is involved in the pathogenesis of obsessive-compulsive disorder (OCD). The loudness dependence of auditory evoked potentials (AEPs) is one of the best validated indicators of the activity of the serotonin system in humans. To explore the validity of the hypothesis of a serotonergic dysfunction in OCD, the loudness dependence of AEPs of 22 medication-free OCD patients were compared with those of 22 age- and gender-matched healthy subjects. Auditory evoked N1/P2 activity to tones of increasing intensity was studied using dipole source analysis. Contrary to the hypothesis, OCD patients and healthy controls did not differ in their LDAEPs of the tangential dipole in particular, located in the primary auditory cortex and closely related to central serotonergic activity. Furthermore, no significant correlation was found between the severity of obsessive-compulsive or depressive symptoms and the loudness dependence of AEPs. These findings do not support the hypothesis of a serotonergic dysfunction in OCD patients.

Adult↗

PubMed2000

The loudness dependency of the auditory evoked N1/P2-component as a predictor of the acute SSRI response in depression.

RATIONALE: A serotonergic dysfunction is supposed to play a pathogenetic role in depression, but there is a considerable number of non-responders in the acute treatment of depression with serotonergic agents like SSRI. Thus, an indicator of central serotonergic activity could lead to a more specific pharmacological treatment of depression. In animal and human data there is a growing amount of evidence that a strong loudness dependency of late auditory evoked potentials (LDAEP) is an indicator of low serotonergic activity and vice versa. OBJECTIVE: In 29 depressive inpatients (DSM-III-R diagnosis 296.x in 28 patients, 300.4 in one patient), the hypothesis was tested that a strong LDAEP prior to treatment can predict a better clinical outcome under SSRI treatment over 4 weeks. RESULTS: Patients with a strong pre-treatment LDAEP had a significantly greater decrease of depressive symptoms (Hamilton Scale for Depression) after 4 weeks than patients with a flat LDAEP. Significantly more responders fell into the group with a high LDAEP. Contrary to what might be expected, a second recording in a subsample of 19 patients after 4 weeks of treatment failed to show changes in the LDAEP. CONCLUSION: Our finding confirms the hypothesis that a strong LDAEP, indicating a low serotonergic activity, is related to a favorable response to acute SSRI treatment in depression. The LDAEP is a promising tool for the prediction of response to serotonin agonists in depression and it seems to be of clinical importance.

Acoustic Stimulation↗

PubMed2000

Dipole localization of P300 and normal aging.

At present, our understanding of how normal aging affects in vivo brain function is rudimentary. Therefore, the aim of the present study was to investigate age effects on auditory P300 topography. A recently developed dipole source model for P300 distinguishes overlapping P300 subcomponents and enhances reliability as well as validity of the measurement. 67 healthy subjects were examined using the P300 dipole model in addition to the scalp data measurement. The results show that P300 subcomponents reflect functionally different processes concerning age changes of P300 activities. Temporo-parietal P300 is smaller in older subjects, whereas frontal P300 is not attenuated. Age affected both P300 subcomponents' latencies. Therefore, the functionally different alteration of P300 subcomponents might be the reason for P300 topography changes with the P300 maximum more frontally in older age.

Acoustic Stimulation↗

PubMed2000

Lithium-induced EEG changes in patients with affective disorders.

In 12 patients with affective disorders (ICD-10: F31, F32, F33), EEGs were recorded before and after 4.4 months of lithium treatment. Effects of lithium on the EEG were analyzed by power spectral analysis controlled for vigilance. We found (1) an increase in relative power in both delta and theta band which was related to the lithium plasma level, (2) a decrease in relative alpha power especially at occipital leads and (3) a reduction of the dominant alpha frequency. The changes in relative power were more pronounced in the right hemisphere, which is in contrast to the hypothesis of a site-specific localization of lithium effects only in left anterior regions.

Aged↗

PubMed2000

Periodic motor impairments in a case of 48-hour bipolar ultrarapid cycling before and under treatment with valproate.

Motor impairments of psychiatric patients can be assessed with digital recordings of handwriting tasks. The investigation of patients with bipolar affective disorders differentiates intraindividual changes related to the patient's fluctuating affective states. An unmedicated 67-year-old male with 48-hour bipolar ultrarapid cycling was investigated during 8 consecutive days of ultrarapid cycling and 4 weeks later, after remission under treatment with valproate. The handwriting skills of the patient followed the same rhythmic changes of the psychopathology in the first part of the study and a steady pattern in the second phase, after remission. Therefore, it can be assumed that the handwriting skills reflect a state marker of the disease. Poorer handwriting skills on the manic days, as compared to the depressive ones, support the hypothesis of a low arousal in manic patients.

Aged↗

PubMed2000

Identifying psychiatric patients with serotonergic dysfunctions by event-related potentials.

The increasing knowledge concerning anatomical structures and cellular processes underlying event-related potentials (ERP) as well as methodological advances in ERP data analysis (e.g. dipole source analysis) is beginning to bridge the gap between ERP and neurochemical aspects. Reliable indicators of the serotonin system are urgently needed because of its role in pathophysiology and as target of pharmacotherapeutic interventions in psychiatric disorders. Converging arguments from preclinical and clinical studies support the hypothesis that the loudness dependence of the auditory evoked N1/P2-response (LDAEP) is regulated by the level of central serotonergic neurotransmission. Dipole source analysis represents an important methodological advance in this context, because the two N1/P2-subcomponents, generated by the primary and secondary auditory cortex known to be differentially innervated by serotonergic fibres, can be separated. A pronounced LDAEP of primary auditory cortices is supposed to reflect low central serotonergic neurotransmission, and vice versa. LDAEP is a parameter with potential clinical value since subgroups of patients with a serotonergic dysfunction can be identified and can be treated more specifically. In depressed patients, a significant relationship between strong LDAEP, indicating low serotonergic function, and a favourable response to SSRI has been found. Additionally, there is evidence from several studies with patients with affective disorders that a strong LDAEP predicts favourable response to a preventive lithium treatment.

Antimanic Agents↗

PubMed2000

Clinical and biological findings in a case with 48-hour bipolar ultrarapid cycling before and during valproate treatment.

BACKGROUND: The rare cases of patients with 48-hour ultrarapid cycling allow close investigation of mood cycles in affective disorders, because rhythmic changes in psychopathologic state and biological parameters happen very precisely. METHOD: A 67-year-old white man who had experienced bipolar 48-hour ultrarapid cycling (DSM-IV 296.80) for several years was studied without any medication and then again studied 4 weeks later during treatment with valproate (1800 mg/day). RESULTS: Objective and self ratings revealed pronounced manic states 1 day and depressed states the following day, which were found to be accompanied by rhythmic fluctuations in behavior and electroencephalographic parameters, blood cortisol and growth hormone levels (both elevated on depressive days), and urinary metanephrine (dopamine metabolite) and norepinephrine levels (both elevated on manic days). Using single photon emission computed tomography, regional blood flow in the left thalamus was lower than in the right thalamus on the manic day, while symmetric perfusion of the thalamus was found on the depressive day. Under valproate treatment, the patient remitted completely, and significant rhythmic changes in most of the biological parameters were no longer detectable. CONCLUSION: The biological findings in this patient with bipolar 48-hour ultrarapid cycling, which correspond to those in other types of affective disorders, suggest that disturbances in the diencephalon-pituitary axis may be especially correlated to pathologic changes of mood.

Aged↗

PubMed1999

Electrical stimulation of rat medial prefrontal cortex enhances forebrain serotonin output: implications for electroconvulsive therapy and transcranial magnetic stimulation in depression.

Decreased activity of the prefrontal cortex (PFC), as well as reduced serotonergic neurotransmission, is considered as a characteristic feature of major depression. The mechanism by which electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS) achieve their antidepressant effects may involve changes in PFC activity. It is, however, still unclear whether these changes are accompanied by increased synaptic availability of serotonin (5-HT). In the present study, 5-HT efflux in the rat ventral hippocampus and amygdala was analyzed using in vivo microdialysis during low-current electrical stimulation of PFC and other cortical regions. Electrical stimulation of the medial PFC produced current-dependent increases in limbic 5-HT output in both urethane-anesthetized and behaving rats. No effects on 5-HT levels were seen after comparable stimulation of either the lateral parts of the PFC, the medial precentral area, the primary motor cortex or the parietal cortex. This pronounced regional specificity of the effect of medial PFC stimulation on limbic 5-HT output suggests that activation of this particular area might play a crucial role in such antidepressant treatments as ECT and TMS.

Amygdala↗

PubMed1999

Auditory evoked potentials reflect serotonergic neuronal activity--a study in behaving cats administered drugs acting on 5-HT1A autoreceptors in the dorsal raphe nucleus.

A valid indicator of central serotonergic neurotransmission would be useful for various diagnostic and psychopharmacological purposes in psychiatry. However, known peripheral serotonergic measures only partially reflect serotonergic function in the brain. Previous findings suggest that the intensity dependence of auditory evoked potentials (AEPs) is closely related to central serotonergic activity. The present study examines the effects of microinjection of a 5-HT1A agonist (8-OH-DPAT) and a 5-HT1A antagonist (spiperone) into the dorsal raphe nucleus (DRN) on AEP recorded epidurally from the primary and secondary auditory cortex in behaving cats. We found a stronger intensity dependence only of AEP from the primary auditory cortex after 8-OH-DPAT, which inhibits the firing rate of serotonergic DRN neurons, and a weaker intensity dependence after spiperone, which increases serotonergic cell firing, as compared to baseline measurements. These results demonstrate that the intensity dependence of AEP is inversely related to serotonergic neuronal activity and that it may be a promising tool for assessing central serotonergic function in humans (e.g., identifying patients with low serotonergic neurotransmission).

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1997

Auditory-evoked potentials as indicator of brain serotonergic activity--first evidence in behaving cats.

Due to the increasing importance of the central serotonergic neurotransmission for pathogenetic concepts and as a target of pharmacotherapeutic interventions in psychiatry, reliable indicators of this system are needed. Several findings from basic and clinical research suggest that the stimulus intensity dependence of auditory evoked potentials (AEP) may be such an indicator of behaviorally relevant aspects of serotonergic activity (Hegerl and Juckel 1993, Biol Psychiatry 33:173-187). In order to study this relationship more directly, epidural recordings over the primary and secondary auditory cortex were conducted in chronically implanted cats under intravenous (i.v.) administration of drugs influencing the serotonergic and other modulatory systems (8-OH-DPAT, m-CPP, ketanserin, DOI, apomorphine, atropine, clonidine). The intensity dependence of the cat AEP component with the highest functional similarity to this of the N1/P2-component in humans was significantly changed by influencing 5-HT1a and 5-HT2 receptors, but not 5-HT1c receptors. This serotonergic modulation of the intensity dependence was only found for the primary auditory cortex which corresponds to the known different innervation of the primary and secondary auditory cortex by serotonergic fibers. Our study supports the idea that the intensity dependence of AEP could be a valuable indicator of brain serotonergic activity; however, this indicator seems to be of relative specificity because at least cholinergic effects on the intensity dependence were also observed.

Animals↗

PubMed1996

Residual symptoms and P300 in schizophrenic outpatients.

A reduced P300 amplitude has often been found to be related to schizophrenic psychopathology. It is still unclear, however, whether this relationship is trait- or state-dependent. We investigated 88 stabilized schizophrenic outpatients during a 2-year follow-up period. Multivariate analyses revealed that patients who had reduced P300 amplitudes showed pronounced residual symptoms, especially thought disorder (Brief Psychiatric Rating Scale). Intraindividual changes in that psychopathology were not correlated to corresponding changes of the P300 amplitude, so the relationship between schizophrenic psychopathology and P300 amplitude appears to be, at least in part, trait-dependent. A reduced P300 amplitude may characterize a subgroup of schizophrenic patients with a disposition to cognitive disturbances and incomplete remissions.

Adult↗

PubMed1996

Serotonergic ethanol effects and auditory evoked dipole activity in alcoholic and healthy subjects.

Ethanol has central serotonergic effects that may be of pathogenetic importance in a subgroup of alcohol-dependent patients with a central serotonergic hypofunction. Recent results indicate that pronounced amplitude increases of auditory evoked responses (tangential dipoles, N1/P2 component) with increasing stimulus intensity (loudness) may be an indicator of such a low serotonergic neurotransmission. Because of its serotonin-agonistic effects, ethanol can be expected to decrease this intensity dependence. Twenty-eight alcoholic patients were studied both in the intoxication phase and after 1 week of withdrawal. A reduced intensity dependence of the tangential dipole activity was observed in the intoxicated state. Correspondingly, a reduction of this parameter was found in 14 healthy subjects after an ethanol load (1 g/kg, p.o.).

Adult↗

PubMed1996

Intensity dependence of auditory evoked potentials in behaving cats.

The intensity dependence of auditory evoked potentials (AEPs) recorded epidurally over the primary (AI) and secondary (AII) areas of the auditory cortex was studied in behaving cats during wakefulness, sleep and anesthesia. Four kHz tones of 50, 60, 70, and 80 dB SPL, presented in random order every 2 +/- 0.2 s by a bone conductor, elicited clear changes of the AEP amplitudes with increasing stimulus intensity, but individual components displayed different response curves. AEP components from the AI region showed saturation of their amplitude with stimulus intensity (P13, P34) or no amplitude increase (N19), while amplitude and intensity were linearly related in the AII area. The intensity dependence of the first positive component (P12/P13) was consistently stronger for the AEP recorded from the AI than from the AII area, while later components exhibited no difference between AI and AII. During slow wave sleep, the intensity dependence of this first positive component increased in the two areas, while that of later components decreased. Pentobarbital anesthesia abolished almost all later components and depressed the intensity dependence of the first positive component both in the AI and AII area. These results indicate that (I) clear intensity dependence of AEP exists in the cat auditory cortex and (2) this intensity dependence, especially that of the first positive AEP component, shares functional similarities to the human augmenting/reducing phenomenon in the auditory modality concerning regional differences and sleep-waking cycle.

Acoustic Stimulation↗

PubMed1996

[Event related brain potentials as indicators of neurochemical dysfunctions in psychiatric patients].

The increasing knowledge concerning anatomical structures and cellular processes underlying event-related potentials (ERP) and methodological advances in ERP data analysis are beginning to bridge the gap between ERP and neurochemical aspects. ERP reflect directly postsynaptic effects of cortical neurotransmitters (e.g. GABA, glutamate) and indirectly modulating effects of neuromodulators (e.g. serotonin, acetylcholine) on cortical neuronal functioning and are therefore promising as noninvasive indicators of the functioning of neurochemical systems. Several recent reports are summarised suggesting that quite specific relationships may exist between certain ERP parameters and central cholinergic, noradrenergic and especially serotonergic function. Converging arguments from preclinical and clinical studies are presented supporting the hypothesis that the dependence of the response of primary auditory cortices on stimulus intensity (loudness) is regulated by the level of central serotonergic neurotransmission. This intensity dependence is shown to be of clinical value because, within different diagnostic categories, subgroups of patients with a serotonergic dysfunction can be identified and can be treated more specifically with serotonergic drugs.

Acetylcholine↗