Biomedical subjects

Dieter F Braus

Publications and source records attributed to Dieter F Braus.

At least 19 recordsLinked to original sources

PubMed2006

A simultaneous EEG-fMRI study of painful electric stimulation.

Together with a detailed behavioral analysis, simultaneous measurement of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) permits a better elucidation of cortical pain processing. We applied painful electrical stimulation to 6 healthy subjects and acquired fMRI simultaneously with an EEG measurement. The subjects rated various stimulus properties and the individual affective state. Stimulus-correlated BOLD effects were found in the primary and secondary somatosensory areas (SI and SII), the operculum, the insula, the supplementary motor area (SMA proper), the cerebellum, and posterior parts of the anterior cingulate gyrus (ACC). Perceived pain intensity was positively correlated with activation in these areas. Higher unpleasantness rating was associated with suppression of activity in areas known to be involved in stimulus categorization and representation (ventral premotor cortex, PCC, parietal operculum, insula) and enhanced activation in areas initiating, propagating, and executing motor reactions (ACC, SMA proper, cerebellum, primary motor cortex). Concordant dipole localizations in SI and ACC were modeled. Using the dipole strength in SI, the network was restricted to SI. The BOLD signal change in ACC was positively correlated to the individual dipole strength of the source in ACC thus revealing a close relationship of BOLD signal and possibly underlying neuronal electrical activity in SI and the ACC. The BOLD signal change decreased in SI over time. Dipole strength of the ACC source decreased over the experiment and increased during the stimulation block suggesting sensitization and habituation effects in these areas.

Brain↗

PubMed2006

Serotonin transporter genotype (5-HTTLPR): effects of neutral and undefined conditions on amygdala activation.

BACKGROUND: A polymorphism of the human serotonin transporter gene (SCL6A4) has been associated with serotonin transporter expression and with processing of aversive stimuli in the amygdala. Functional imaging studies show that during the presentation of aversive versus neutral cues, healthy carriers of the short (s) allele showed stronger amygdala activation than long (l) carriers. However, a recent report suggested that this interaction is driven by amygdala deactivation during presentation of neutral stimuli in s carriers. METHODS: Functional MRI was used to assess amygdala activation during the presentation of a fixation cross or affectively aversive or neutral visual stimuli in 29 healthy men. RESULTS: Amygdala activation was increased in s carriers during undefined states such as the presentation of a fixation cross compared with emotionally neutral conditions. CONCLUSIONS: This finding suggests that s carriers show stronger amygdala reactivity to stimuli and contexts that are relatively uncertain, which we propose are stressful.

Adult↗

PubMed2006

Neural correlates of memory confidence.

The present study aimed to shed light on the neural underpinnings of high vs. low memory confidence. To dissociate memory confidence from accuracy, the Deese-Roediger McDermott (DRM) paradigm was employed, which - compared to other memory paradigms - elicits a rather evenly distributed number of high-confident responses across all possible combinations of memory response types (i.e., hits, false alarms, correct rejections, and misses). In the standard DRM procedure, subjects are first presented with thematically interrelated word lists at encoding, which at recognition are intermixed with related and unrelated distractor items. The signature of a false memory or DRM effect is an increased number of high-confident false memories, particularly for strongly related lure items. For the present study, 17 female subjects were administered a verbal DRM task, whereas neural activation was indexed by fMRI. The behavioral analyses confirmed the expected false memory effect: subjects made more high-confident old responses (both hits and false alarms) the closer the items were related to the central list theme. Across all four memory response types, an increase in confidence at recognition was associated with bilateral activation in the anterior and posterior cingulate cortex along with medial temporal regions. In contrast, increments in doubt were solely related to activation in the superior posterior parietal cortex. To conclude, the study provides some evidence for dissociable systems for confidence and doubt.

Adult↗

PubMed2006

Neural correlates of working memory dysfunction in first-episode schizophrenia patients: an fMRI multi-center study.

Working memory dysfunction is a prominent impairment in patients with schizophrenia. Our aim was to determine cerebral dysfunctions by means of functional magnetic resonance imaging (fMRI) in a large sample of first-episode schizophrenia patients during a working memory task. 75 first-episode schizophrenia patients and 81 control subjects, recruited within a multi-center study, performed 2- and 0-back tasks while brain activation was measured with fMRI. In order to guarantee comparability between data quality from different scanners, we developed and adopted a standardized, fully automated quality assurance of scanner hard- and software as well as a measure for in vivo data quality. After these quality-control measures had been implemented, 48 patients and 57 controls were included in the final analysis. During attention-related processes, even when the performance between patients and controls was comparable, there was a recognizable emergence of cerebral dysfunctions with hypoactivations in the ventrolateral prefrontal cortex (VLPFC), in the superior temporal cortex and in the thalamus. During working memory performance, parietal hypoactivations, especially in the precuneus, were prominent and were accompanied by poorer performance in patients. A hyperfrontality emerged in the ventrolateral prefrontal cortex. Hence, results point to a dysfunctional ventrolateral prefrontal-parietal network during working memory in patients, suggesting impairments in basic functions such as retrieval, storage and maintenance. The brain activation pattern of this large and significant sample of first-episode schizophrenia patients indicates an imbalanced system failing to adjust the amount of brain activity required in the cerebral network involved in attention and working memory.

Adolescent↗

PubMed2006

Dissociable systems for gain- and loss-related value predictions and errors of prediction in the human brain.

Midbrain dopaminergic neurons projecting to the ventral striatum code for reward magnitude and probability during reward anticipation and then indicate the difference between actual and predicted outcome. It has been questioned whether such a common system for the prediction and evaluation of reward exists in humans. Using functional magnetic resonance imaging and a guessing task in two large cohorts, we are able to confirm ventral striatal responses coding both reward probability and magnitude during anticipation, permitting the local computation of expected value (EV). However, the ventral striatum only represented the gain-related part of EV (EV+). At reward delivery, the same area shows a reward probability and magnitude-dependent prediction error signal, best modeled as the difference between actual outcome and EV+. In contrast, loss-related expected value (EV-) and the associated prediction error was represented in the amygdala. Thus, the ventral striatum and the amygdala distinctively process the value of a prediction and subsequently compute a prediction error for gains and losses, respectively. Therefore, a homeostatic balance of both systems might be important for generating adequate expectations under uncertainty. Prevalence of either part might render expectations more positive or negative, which could contribute to the pathophysiology of mood disorders like major depression.

Adult↗

PubMed2006

D2 antidopaminergic modulation of frontal lobe function in healthy human subjects.

BACKGROUND: Although the major principles of dopamine (DA) signaling have been well described previously, its precise modulatory impact on the prefrontal cortex (PFC) in humans is poorly understood. Two major neurophysiological models propose segregated functional circuits on the systems level as well as D(1) and D(2) receptor-dependent processing states on the cellular level (two-state model). METHODS: We examined the predictive validity of these models in 10 healthy male volunteers with a haloperidol challenge (HLP). Cortico-striatal-thalamo-cortical (CSTC) motor loop functions were examined during functional magnetic resonance imaging (fMRI) with a sequential finger opposition task. Neuropsychological implications of the two-state model were evaluated with a test battery of D(1)- or D(2)-sensitive prefrontal measures. RESULTS: Analysis of fMRI data revealed a significant HLP-induced blood oxygen level dependent-signal decrease in the sensorimotor striatum and a lateralized activation loss of ipsilateral higher order motor cortices and contralateral cerebellum. Neuropsychological evaluation demonstrated a preferential impairment of D(2)-sensitive functions, whereas D(1) or non-dopaminergic domains were unaffected. CONCLUSIONS: Our data support the hypothesis that mesocortical D(1) and D(2) receptors exert differential influences in the PFC for cognitive function, but the nigrostriatal CSTC network model for the motor domain could not be confirmed.

Adult↗

PubMed2006

Hippocampal-prefrontal encoding activation predicts whether words can be successfully recalled or only recognized.

The main goal of the present fMRI-study was to identify the neural correlates underlying the successful encoding of words which can subsequently be freely recalled or recognized but not recalled. We were particularly interested in common as well as distinct neural substrates of both retrieval modes. To assess qualitatively differently activated brain areas, categorical subsequent memory analyses were applied. In addition, we used linear parametric modulation to detect brain regions associated with "memory-strength". Our findings suggest that the successful verbal encoding of words, which were recognized but not recalled relies on a subset of the regions engaged during successful encoding of freely recalled words. Furthermore, it seems to be dependent on the magnitude of relational binding in a prefrontal-hippocampal circuit whether a word can subsequently be recalled freely or only recognized.

Adult↗

PubMed2006

Combining voxel-based morphometry and diffusion tensor imaging to detect age-related brain changes.

The present study combined optimized voxel-based morphometry and diffusion tensor imaging to detect age-related brain changes. We compared grey matter density maps (grey matter voxel-based morphometry) and white matter fractional anisotropy maps (diffusion tensor imaging-voxel-based morphometry) between two groups of 17 younger and 17 older women. Older women exhibited reduced white matter fractional anisotropy as well as decreased grey matter density most prominently in the frontal, limbic, parietal and temporal lobes. A discriminant analysis identified four frontal and limbic grey and white matter areas that separated the two groups most effectively. We conclude that grey matter voxel-based morphometry and diffusion tensor imaging voxel-based morphometry are well suited for the detection of age-related changes and their combination provides high accuracy when detecting the neural correlates of aging.

Adolescent↗

PubMed2006

Net influx of plasma 6-[18F]fluoro-L-DOPA (FDOPA) to the ventral striatum correlates with prefrontal processing of affective stimuli.

Dopaminergic neurotransmission in the ventral and dorsal striatum interact with central processing of rewarding and reward-indicating stimuli, and may affect frontocortical-striatal-thalamic circuits regulating goal-directed behaviour. Thirteen healthy male volunteers were investigated with multimodal imaging, using the radioligand 6-[(18)F]fluoro-l-DOPA (FDOPA) for positron emission tomography (PET) measurements of dopamine synthesis capacity, and also functional magnetic resonance imaging (fMRI) in a cognitive activation paradigm. We calculated the correlation between FDOPA net blood-brain influx (; ml/g/min) in the ventral and associative dorsal striatum and BOLD signal changes elicited by standardized affectively positive, negative and neutral visual stimuli. The magnitude of in the ventral striatum was positively correlated with BOLD signal increases in the left anterior cingulate cortex and right insular operculum elicited by positive vs. neutral stimuli, but not negative vs. neutral stimuli. In the dorsal striatum, the magnitude of was positively correlated with processing of positive and negative stimuli in the left dorsolateral prefrontal cortex. These findings suggest that dopamine synthesis capacity in the ventral striatum correlates with the attentional processing of rewarding positive stimuli in the anterior cingulate cortex of healthy subjects. Dopaminergic neurotransmission in the associative dorsal striatum has been associated previously with habit learning. The observed correlation between dopamine synthesis capacity in the dorsal striatum and BOLD signal changes in the dorsolateral prefrontal cortex suggests dopaminergic modulation of processing of emotional stimuli in brain areas associated with motor planning and executive behaviour control.

Adult↗

PubMed2006

Blockade of cue-induced brain activation of abstinent alcoholics by a single administration of amisulpride as measured with fMRI.

BACKGROUND: Once alcohol dependence is established, alcohol-associated cues may induce dopamine release in the reward system, which is accompanied by alcohol craving and may lead to relapse. In cocaine addicts, dopamine release in the thalamus was positively correlated with cocaine craving. We tested the effects of the atypical dopamine D(2/3) blocker amisulpride on cue-induced brain activation in a functional magnetic resonance imaging (fMRI) paradigm. METHODS: Alcohol-associated and neutral pictures were presented in a block design to 10 male abstinent alcoholics (1-3 weeks after detoxification) and 10 healthy men during fMRI. The fMRI scans were acquired before and 2 hours after the oral application of 400 mg amisulpride. Before and after each scan, alcohol craving was measured with visual analogue scales. RESULTS: Before the application of amisulpride, alcohol versus control cues elicited a higher blood oxygen level-dependent (BOLD) signal in the left frontal and orbitofrontal lobe, left cingulate gyrus, bilateral parietal lobe, and bilateral hippocampus in alcoholics compared with healthy controls. After amisulpride, alcoholics showed a reduced activation in the right thalamus compared with the first scan. Alcoholics no longer showed significant differences in their cue-elicited BOLD response after amisulpride medication compared with medication-free controls. Self-reported craving was not affected by amisulpride medication. CONCLUSIONS: Amisulpride medication was associated with reduced cue-induced activation of the thalamus, a brain region closely connected with frontostriatal circuits that regulate behavior and may influence relapse risk.

Adult↗

PubMed2005

Disturbance in the neural circuitry underlying positive emotional processing in post-traumatic stress disorder (PTSD). An fMRI study.

This study was designed to investigate the circuitry underlying movie-induced positive emotional processing in subjects with chronic PTSD. Ten male subjects with chronic PTSD and ten matched controls were studied. In an fMRI-paradigm a sequence of a wellknown Walt Disney cartoon with positive emotional valence was shown. PTSD subjects showed an increased activation in the right posterior temporal, precentral and superior frontal cortex. Controls recruited more emotion-related regions bilateral in the temporal pole and areas of the left fusiform and parahippocampal gyrus. This pilot study is the first to reveal alterations in the processing of positive emotions in PTSD possibly reflecting a neuronal correlate of the symptom of emotional numbness in PTSD.

Adult↗

PubMed2005

Severity of nicotine dependence modulates cue-induced brain activity in regions involved in motor preparation and imagery.

RATIONALE: In nicotine-dependent subjects, cues related to smoking elicit activity in brain regions linked to attention, memory, emotion and motivation. Cue-induced brain activation is associated with self-reported craving but further correlates are widely unknown. OBJECTIVES: This study was conducted to investigate whether brain activity elicited by smoking cues increases with severity of nicotine dependence and intensity of cue-elicited craving. METHODS: Ten healthy male smokers whose degree of nicotine dependence ranged from absent to severe were investigated. Visual smoking cues and neutral stimuli were presented in a block design during functional magnetic resonance imaging (fMRI). Using multiple linear regression analysis, the blood oxygen level dependent (BOLD) response to smoking cues was correlated with severity of nicotine dependence assessed with the Fagerström Test of Nicotine Dependence (FTND) and with cue-induced craving. RESULTS: Significant positive correlations between the BOLD activity and FTND scores were found in brain areas related to visuospatial attention (anterior cingulate cortex, parietal cortex, parahippocampal gyrus and cuneus) and in regions involved in motor preparation and imagery (primary and premotor cortex, supplementary motor area). Intensity of cue-induced craving was significantly associated with greater BOLD activation in mesocorticolimbic areas engaged in incentive motivation and in brain regions related to episodic memory. CONCLUSIONS: Our study suggests that severity of nicotine dependence and intensity of craving are independently associated with cue-induced brain activation in separate neuronal networks. The observed association between severity of dependence and brain activity in regions involved in allocation of attention, motor preparation and imagery might reflect preparation of automated drug taking behavior thereby facilitating cue-induced relapse.

Adult↗

PubMed2005

Catechol-O-methyltransferase val158met genotype affects processing of emotional stimuli in the amygdala and prefrontal cortex.

Catechol-O-methyltransferase (COMT) degrades the catecholamine neurotransmitters dopamine, epinephrine, and norepinephrine. A functional polymorphism in the COMT gene (val158met) accounts for a fourfold variation in enzyme activity. The low-activity met158 allele has been associated with improved working memory but with higher risk for anxiety-related behaviors. Using functional magnetic resonance imaging, we assessed the effects of COMT genotype on brain activation by standardized affective visual stimuli (unpleasant, pleasant, and neutral) in 35 healthy subjects. The analysis of genotype effects was restricted to brain areas with robust activation by the task. To determine genedose effects, the number of met158 alleles (0, 1, or 2) was correlated with the blood oxygen level-dependent (BOLD) response elicited by pleasant or unpleasant stimuli compared with neutral stimuli. COMT genotype had no significant impact on brain activation by pleasant stimuli but was related to the neural response to unpleasant stimuli: reactivity to unpleasant stimuli was significantly positively correlated with the number of met158 alleles in the limbic system (left hippocampus, right amygdala, right thalamus), connected prefrontal areas (bilateral ventrolateral prefrontal cortex, right dorsolateral prefrontal cortex), and the visuospatial attention system (bilateral fusiform gyrus, left inferior parietal lobule). Genotype explained up to 38% of interindividual variance in BOLD response elicited by unpleasant stimuli. We conclude that (1) genetic variations can account for a substantial part of interindividual variance in task-related brain activation and that (2) increased limbic and prefrontal activation elicited by unpleasant stimuli in subjects with more met158 alleles might contribute to the observed lower emotional resilience against negative mood states.

Adult↗

PubMed2005

Correlation of stable elevations in striatal mu-opioid receptor availability in detoxified alcoholic patients with alcohol craving: a positron emission tomography study using carbon 11-labeled carfentanil.

BACKGROUND: The pleasant effects of food and alcohol intake are partially mediated by mu-opiate receptors in the ventral striatum, a central area of the brain reward system. Blockade of mu-opiate receptors with naltrexone reduces the relapse risk among some but not all alcoholic individuals. OBJECTIVE: To test the hypothesis that alcohol craving is pronounced among alcoholic individuals with a high availability of mu-opiate receptors in the brain reward system. DESIGN: Patients and comparison sample. The availability of central mu-opiate receptors was measured in vivo with positron emission tomography (PET) and the radioligand carbon 11-labeled carfentanil in the ventral striatum and compared with the severity of alcohol craving as assessed by the Obsessive Compulsive Drinking Scale (OCDS). SETTING: Hospitalized care. PARTICIPANTS: Volunteer sample of 25 male alcohol-dependent inpatients assessed after detoxification of whom 12 underwent PET again 5 weeks later. Control group of 10 healthy men. MAIN OUTCOME MEASURES: After 1 to 3 weeks of abstinence, the availability of mu-opiate receptors in the ventral striatum, including the nucleus accumbens, was significantly elevated in alcoholic patients compared with healthy controls and remained elevated when 12 alcoholic patients had these levels measured 5 weeks later (P<.05 corrected for multiple testing). Higher availability of mu-opiate receptors in this brain area correlated significantly with the intensity of alcohol craving as assessed by the OCDS. CONCLUSIONS: Abstinent alcoholic patients displayed an increase in mu-opiate receptors in the ventral striatum, including the nucleus accumbens, which correlated with the severity of alcohol craving. These findings point to a neuronal correlate of alcohol urges.

Adult↗

PubMed2005

Long-term behavioural changes after unilateral stereotactic cingulotomy in a case of therapy-resistant alcohol dependence.

We report the case of a female patient who had undergone a unilateral stereotactical anterior cingulotomy (AC) 20 years previously because of refractory alcohol dependence. After AC, the drinking behaviour switched from a chronic to an episodic one with fast losses of control accompanied by abnormal oral impulse-control behaviour. Relapses were stress- but not cue-induced and followed by long-term intervals of abstinence. In addition to an intended lesion of the left dorsal anterior cingulate cortex (ACC), MR images showed additional lesions within the left caudate body and the dorsal medial thalamic nucleus. Applying a neuropsychological test battery, we found disturbed divided attention and impaired executive function. From this, we conclude that the complex lesion pattern may contribute to some of the behavioural changes seen in our patient after AC. This hypothesis is supported by the neuropsychological deficits and the fact that the neuronal circuits, impaired by the lesions, are involved in addiction-specific behaviour. This case report further emphasizes the key role of the ACC and its connections in the maintenance of dependent behaviour.

Aged↗

PubMed2005

Further evidence for altered cerebellar neuronal integrity in schizophrenia.

OBJECTIVE: The authors' goal was to investigate the distribution of metabolites and voxel composition in the pons and three cerebellar subregions and compare metabolite integral values and differences in voxel composition between patients with schizophrenia and healthy subjects. METHOD: Proton magnetic resonance spectroscopic imaging was used to study the cerebellum and pons of 14 patients with schizophrenia and 14 healthy comparison subjects. RESULTS: The voxel composition was not significantly different between the groups, but the patients with schizophrenia had significantly lower N-acetylaspartate levels in the cerebellar cortex and vermis. CONCLUSIONS: The lower integral value of N-acetylaspartate in the cerebellar cortex and the vermis of patients with schizophrenia supports the theory of a dysfunctional corticocerebellar-thalamic-cortical circuit in schizophrenia.

Adult↗

PubMed2004

Amygdala-prefrontal coupling depends on a genetic variation of the serotonin transporter.

Major depression is conditionally linked to a polymorphism of the human serotonin transporter gene (SLC6A4). During the presentation of aversive, but not pleasant, pictures, healthy carriers of the SLC6A4 short (s) allele showed stronger activation of the amygdala on functional magnetic resonance imaging. s carriers also showed greater coupling between the amygdala and the ventromedial prefrontal cortex, which may contribute to the abnormally high activity in the amygdala and medial prefrontal cortex seen in major depression.

Aged↗

PubMed2004

Late-onset depression with mild cognitive deficits: electrophysiological evidences for a preclinical dementia syndrome.

Mild cognitive impairment (MCI) is present in up to 60% of patients with late-onset depression and constitutes a major diagnostic problem in geriatric psychiatry. Searching for sensitive markers for the detection of early brain changes suggestive of dementia, we compared this depressive risk population with mildly to moderately demented patients and cognitively unimpaired depressed patients using EEG power and coherence. We found a considerable similarity between Alzheimer's disease patients and cognitively impaired depressed patients regarding the cognitive profile and EEG pattern. Changes in EEG power and coherence at frontotemporal leads in depressive patients with MCI thereby allowed discrimination from cognitively unimpaired patients with a sensitivity of 88% and a specifity of 81%.

Age of Onset↗