Biomedical subjects

Wolfgang Weber-Fahr

Publications and source records attributed to Wolfgang Weber-Fahr.

10 recordsLinked to original sources

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↗

PubMed2005

Monitoring the effects of chronic alcohol consumption and abstinence on brain metabolism: a longitudinal proton magnetic resonance spectroscopy study.

BACKGROUND: This study focused on metabolic brain alterations in recently detoxified alcohol-dependent patients (S1) and their possible reversibility after 3 (S2) and 6 months (S3) of abstinence. METHODS: Thirty-three alcohol-dependent patients and 30 healthy control subjects were studied with multislice proton magnetic resonance spectroscopic imaging (echo time = 135 msec at 1.5 T at three time points). RESULTS: In the patient group, we found that choline-containing compounds (Ch) in three frontal and cerebellar subregions at S1 were significantly below normal, whereas N-acetyl aspartate (NAA) differences did not reach significance but showed a trend toward below-normal values in frontal white matter. Abstinent patients showed a significant increase of Ch in all subregions at S2. At S3, no further significant metabolite changes in abstinent patients compared with S2 could be detected. No significant increase of NAA could be detected at follow-up. CONCLUSIONS: The increase of the Ch signal in the follow-up measurement after 3 months in abstinent alcohol-dependent patients supports the hypotheses of an alcohol- or alcohol detoxification-induced altered cerebral metabolism of lipids in membranes or myelin, which seems to be reversible with duration of alcohol abstinence.

Adult↗

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

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↗

PubMed2004

Cue-induced activation of the striatum and medial prefrontal cortex is associated with subsequent relapse in abstinent alcoholics.

RATIONALE: Animal experiments have provided evidence that the striatum and medial prefrontal cortex play a predominant role in the acquisition and maintenance of drug-seeking behavior. OBJECTIVES: Alcohol-associated stimuli that were regularly paired with alcohol intake may become conditioned cues and elicit a motivational response that triggers relapse in alcohol-dependent patients. METHODS: We used functional magnetic resonance imaging and visual alcohol-associated and control cues to assess brain activation in ten abstinent alcoholics and control subjects. Patients were followed for 3 months, and alcohol intake was recorded. RESULTS: Alcohol-related versus neutral visual stimuli activated the putamen, anterior cingulate and adjacent medial prefrontal cortex in alcoholics compared with healthy controls. Cue-induced activation of these brain areas was pronounced in the five alcoholics who subsequently relapsed during the observation period. A multiple regression analysis showed that, in alcoholics, the amount of subsequent alcohol intake was associated with the intensity of cue-induced brain activation but not the severity of alcohol craving, amount of previous alcohol intake or duration of abstinence before scanning. CONCLUSIONS: This pilot study showed that cue-induced activation of the anterior cingulate, medial prefrontal cortex and striatum may play a role in the attribution of incentive salience to alcohol-associated stimuli, thus increasing the motivational value and attentional processing of alcohol cues. Functional brain imaging may help to identify a group of alcoholics with an otherwise undetected high risk of relapse.

Adult↗

PubMed2003

Haloperidol challenge in healthy male humans: a functional magnetic resonance imaging study.

Functional magnetic resonance imaging (fMRI) was used to determine the acute blood oxygen level dependent effect (BOLD) of neuroleptic drugs in healthy male subjects. Using a robust simultaneous visuo-acoustic stimulation paradigm fMRI measurements were obtained prior to as well as 1 h and 24 h after intravenous infusion of 5 mg haloperidol to six healthy young men. After the administration, subjects showed significantly reduced BOLD contrast in the middle occipital gyrus while BOLD contrast was increased in the lingual gyrus. This pattern normalised within 24 h. Our results emphasise the necessity to control for interactions through acute medication and confirm fMRI as a non-invasive method for studying cerebral psychopharmacological effects.

Acoustic Stimulation↗

PubMed2003

Multiregional 1H-MRSI of the hippocampus, thalamus, and basal ganglia in schizophrenia.

BACKGROUND: The hippocampus, thalamus and basal ganglia are among the brain regions of major interest in schizophrenia. AIMS: The purpose of this study was to corroborate previous findings of reduced N-acetylaspartate in the hippocampal and thalamic regions and to investigate possible metabolite changes in the putamen in schizophrenia. METHOD: MRSI study of the thalamus, basal ganglia, and hippocampus in 13 schizophrenic patients under stable medication and age-matched healthy controls. RESULTS: A decrease of the N-acetylaspartate signal was found in the hippocampal region and the thalamus but not in the putamen of patients compared to controls. No significant group differences in the signals from creatine and phosphocreatine, and choline-containing compounds were found in the hippocampal region and the putamen but the signal from choline-containing compounds was decreased in the thalamus of patients. CONCLUSION: Metabolic processes in the basal ganglia of schizophrenic patients seem to be opposite the hippocampal and thalamus findings.

Adult↗

PubMed2002

Sensory information processing in neuroleptic-naive first-episode schizophrenic patients: a functional magnetic resonance imaging study.

BACKGROUND: Schizophrenic disorders are thought to involve widespread abnormalities in information processing. The present study used functional magnetic resonance imaging and a simple and robust paradigm that involved auditory and visual activation to examine basic sensory input circuits. Our aim was to determine which stages of the input processing network are disturbed in first-episode schizophrenic patients. METHODS: Twelve neuroleptic-naive inpatients (paranoid subtype) were compared with 11 healthy subjects by means of echo-planar functional magnetic resonance imaging. In a block design, the paradigm included the simultaneous presentation of a moving 6-Hz checkerboard and auditory stimuli in the form of drumbeats. The subjects were asked to simply look and listen. RESULTS: In comparison with control subjects, patients showed reduced activation in the right thalamus, the right prefrontal cortex, and the parietal lobe (restricted to the dorsal visual pathway) bilaterally. There were no notable differences in the primary visual cortex or the object-specific occipitotemporal pathway. In addition, patients presented with a reduced signal change to auditory stimulation in the left acoustic cortex. CONCLUSIONS: The present study supports the concept of widespread cortical and subcortical deficits in schizophrenia. Our findings suggest abnormal functioning early in the information processing and in high-order association cortices already at illness onset, before the administration of medication or the most confounding effects of illness duration. The main regions have been implicated in visual motion perception and discrimination as well as in attention to sensorial events and perceptual synthesis.

Acoustic Stimulation↗

PubMed2002

Functioning and neuronal viability of the anterior cingulate neurons following antipsychotic treatment: MR-spectroscopic imaging in chronic schizophrenia.

Magnetic resonance spectroscopic imaging provides a non-invasive approach for testing the hypothesis that neuronal function can improve under atypical antipsychotic medication leading to improvement in cognitive function. We studied two groups of schizophrenic patients, one treated exclusively with typical neuroleptics, the other with atypical medications. 1H MR-spectroscopic imaging of the anterior cingulate gyrus was performed in all patients. Perseveration errors in the Wisconsin Card Sorting Test (WCST) served as an additional marker for cingulate gyrus function. Our results showed that N-acetylaspartate (NAA), a measure of neuronal function, was closely correlated with perseveration errors seen on the WCST. Patients treated with atypical medications had fewer errors on the WCST and higher NAA levels than those on typical medications, and there was a correlation between the time treated with atypical medication, higher NAA levels and better test performance. These results suggest that atypical antipsychotics modify the function of anterior cingulate neurons in a specific manner.

Adult↗