Biomedical subjects

Klaus Hoenig

Publications and source records attributed to Klaus Hoenig.

6 recordsLinked to original sources

PubMed2005

Impaired prepulse inhibition of acoustic startle in obsessive-compulsive disorder.

BACKGROUND: Animal and clinical studies suggest that impaired sensorimotor gating, as assessed with the prepulse inhibition (PPI) paradigm, may result from dysfunctional frontostriatal brain circuits and from neurochemical alterations which are also implied in the pathophysiology of obsessive-compulsive disorder (OCD). However, there is only preliminary evidence about impaired PPI in OCD so far. METHODS: Acoustic PPI was measured in 30 OCD patients and 30 matched healthy controls with a paradigm using different prepulse intensities. Psychopathology assessment included ratings for obsessions, compulsions, and depression. RESULTS: PPI was reduced in OCD patients, and this deficit was most pronounced for most intense (16 dB(A)) prepulses, where mean PPI was 39.6% in unmedicated patients (n = 4), 45.8% in medicated patients, and 58.9% in controls. No group differences were observed with regard to the habituation of acoustic startle magnitude. Startle measures were generally not associated with clinical measures, although such associations may have been obscured by medication effects. CONCLUSIONS: The present study confirms deficient central inhibitory functioning in patients with OCD and supports the model of deficient frontostriatal circuits in OCD. The relationship of PPI deficits to pharmacological and behavioral treatment and to possible subtypes of OCD merits further study.

Acoustic Stimulation↗

PubMed2005

Functional 3.0-T MR assessment of higher cognitive function: are there advantages over 1.5-T imaging?

PURPOSE: To compare cortical activation patterns associated with manual motor decision tasks at 1.5- and 3.0-T functional magnetic resonance (MR) imaging. MATERIALS AND METHODS: The local ethics committee approved this study, and informed written consent was obtained. Ten right-handed healthy volunteers (eight men and two women; mean age, 35 years +/- 7 [standard deviation]) underwent functional MR imaging twice, once at 1.5 T and once at 3.0 T, while performing cognitive tasks that demanded manual motor decisions (letter-finger matching and lexical and semantic decisions). While stimulus presentation was blocked, an event-related model was employed to analyze subjects' individual responses. A group analysis of functional data was performed with a t test of 1.5- and 3.0-T results in the 10 subjects. RESULTS: Manual motor decisions activated a widespread network of motor- (primary motor, posterior parietal) and decision-related areas (superior frontal cortex or anterior cingulate) at both field strengths (P <.05, corrected). Moreover, additional functional activation was detected in medial (supplementary motor area) and dorsal premotor regions (P <.05, corrected) at 3.0-T functional MR imaging, which was not detectable with corresponding 1.5-T imaging. The mean t value for peak voxels in activated areas detectable with both systems was 1.3 times larger at 3.0 T than that at 1.5 T. CONCLUSION: Functional 3.0-T MR imaging allows detection of additional activation in cortical areas involved in higher executive motor functions compared with functional 1.5-T MR imaging.

Adult↗

PubMed2005

Mediotemporal contributions to semantic processing: fMRI evidence from ambiguity processing during semantic context verification.

The medial temporal lobe (MTL) is well known to be crucial for various types of memory; however, controversy remains as to which of its substructures contribute to semantic processing and, if so, to what extent. The current study addresses the issue of MTL contributions to semantic processing during lexico-semantic ambiguity processing by using functional magnetic resonance imaging (fMRI) in combination with a context verification task (CVT). The CVT required decisions on the semantic fit of congruent and incongruent target words to the overall meaning of preceding sentential contexts with and without semantic ambiguity. In two of the four experimental conditions (congruent homographic, incongruent homographic), target decisions were critically dependent on the successful processing of prior sentence-final lexico-semantic ambiguity. Semantic context verification per se evidenced bilateral activations of the hippocampus that were part of a functional network including inferior prefrontal and superior parietal cortices. Commonalities in activation differences pertaining to the specific cognitive component of lexico-semantic ambiguity processing were found in a left temporal lobe network that comprised activation foci in the temporal pole, the parahippocampal and fusiform gyri. The present results suggest that the hippocampus may well contribute to semantic processing, namely by a mnemonic function that serves to link the target meaning representation with the meaning of a prior sentence context. Contrary to previous reports from human lesion studies, the present findings further suggest, that the specific cognitive component of lexico-semantic ambiguity processing is neither dependent on the hippocampus nor exclusively subserved by the temporal pole, but also recruits an associative semantic memory function from the parahippocampal gyrus as well as a more general (bottom-up) semantic function from the fusiform gyrus.

Adult↗

PubMed2004

Effects of serotonergic and noradrenergic antidepressants on auditory startle response in patients with major depression.

RATIONALE: Amplitude, habituation and prepulse inhibition (PPI) of the acoustic startle response (ASR) in rodents and humans are sensitive to psychotropic drugs. Studies with rodents suggest that an increase or decrease in serotonin level in the brain alters several modalities of the ASR. So far, little is known about serotonergic and noradrenergic startle modulation in humans. OBJECTIVE: This study was designed to investigate the effects of the selective serotonin uptake inhibitor sertraline versus the selective noradrenalin uptake inhibitor reboxetine on magnitude, habituation and PPI of ASR in patients with major depression. METHODS: We studied ASR in 23 patients with the diagnosis of major depression according to DSM-IV who were randomly treated either with sertraline or with reboxetine. Initially, ASR assessment was carried out when patients were drug-free for at least 2 weeks and again after 14 days of treatment. RESULTS: The habituation of ASR was strongly attenuated by sertraline and not significantly altered by reboxetine. None of the substances altered the startle reactivity. In addition, PPI was not altered by sertraline, but reboxetine tended to decrease PPI. The startle reactivity at baseline was correlated with improvement of depressive symptoms at the end of the study. CONCLUSION: These results provide the first evidence for different effects of noradrenergic and serotonergic antidepressants on the startle response in depressed patients.

Acoustic Stimulation↗

PubMed2004

Prepulse inhibition and habituation of acoustic startle response in male MDMA ('ecstasy') users, cannabis users, and healthy controls.

Chronic administration of 3,4-methylenedioxymethamphetamine (MDMA) is associated with long-term depletion of serotonin (5-HT) and loss of 5-HT axons in the brains of rodents and nonhuman primates. Despite the broad database concerning the selective serotonergic neurotoxicity of recreational MDMA consumption by humans, controversy still exists with respect to the question of whether the well-known functional consequences of these neurotoxic effects, such as memory impairment, were caused by chronic 5-HT deficiency. Habituation and prepulse inhibition (PPI) of the acoustic startle response (ASR) can be used as a marker of central serotonergic functioning in rodents and humans. Thus, we investigated the functional status of the central serotonergic system in chronic but abstinent MDMA users by measuring PPI and habituation of ASR. PPI and habituation of ASR were measured in three groups. The first group (MDMA group) included 20 male drug-free chronic users of MDMA; the second group (cannabis group) consisted of 20 male drug-free chronic users of cannabis; and the third group (healthy controls) comprised 20 male participants with no history of illicit drug use. Analysis revealed significantly increased PPI of MDMA users compared to those of cannabis users and healthy controls. Cannabis users and healthy controls showed comparable patterns of PPI. There were no differences in habituation among the three groups. These results suggest that the functional consequences of chronic MDMA use may be explained by 5-HT receptor changes rather than by a chronic 5-HT deficiency condition. Use of cannabis does not lead to alterations of amplitude, habituation, or PPI of ASR.

Acoustic Stimulation↗

PubMedDate not supplied

Curved-surface projection: an alternative method for visualizing functional MR imaging results.

Curved-surface projection (CSP) is a new technique for visualizing functional MR imaging data. This technique helps in identifying anatomic structures by demonstrating the whole gyral and sulcal pattern of the brain at once. Compared with other techniques, CSP preserves the spatial relation of eloquent areas to lesions. Especially in neurosurgical patients with space-occupying lesions, CSP helps in assigning the anatomy to its function.

Astrocytoma↗