PubMed Health⌕ Search

Biomedical subjects

Manfred Herrmann

Publications and source records attributed to Manfred Herrmann.

11 recordsLinked to original sources
PubMed2006

Modulation of prefrontal cortex activation by emotional words in recognition memory.

We employed event-related functional magnetic resonance imaging to examine emotional valence effects on verbal recognition memory. Using a yes/no recognition task, we focussed on prefrontal cortex responses to positive, negative and neutral words. Behavioral data confirmed enhanced processing of emotional items and functional magnetic resonance imaging revealed different subregions in the prefrontal cortex supporting retrieval of emotional words. Activations in the right mid-ventrolateral prefrontal cortex correlated with the correct retrieval conditions for negative words, whereas the right ventromedial and orbitofrontal prefrontal cortex showed enhanced responses to positive words. Additionally, differences between old and new items mainly affected bilateral orbitofrontal regions when processing positive words. The results are discussed in terms of higher monitoring demands owing to familiarity-based recognition bias for emotional words.

Adult↗
PubMed2006

Comparison of two Simon tasks: neuronal correlates of conflict resolution based on coherent motion perception.

The present study aimed at characterizing the neural correlates of conflict resolution in two variations of the Simon effect. We introduced two different Simon tasks where subjects had to identify shapes on the basis of form-from-motion perception (FFMo) within a randomly moving dot field, while (1) motion direction (motion-based Simon task) or (2) stimulus location (location-based Simon task) had to be ignored. Behavioral data revealed that both types of Simon tasks induced highly significant interference effects. Using event-related fMRI, we could demonstrate that both tasks share a common cluster of activated brain regions during conflict resolution (pre-supplementary motor area (pre-SMA), superior parietal lobule (SPL), and cuneus) but also show task-specific activation patterns (left superior temporal cortex in the motion-based, and the left fusiform gyrus in the location-based Simon task). Although motion-based and location-based Simon tasks are conceptually very similar (Type 3 stimulus-response ensembles according to the taxonomy of [Kornblum, S., Stevens, G. (2002). Sequential effects of dimensional overlap: findings and issues. In: Prinz, W., Hommel., B. (Eds.), Common mechanism in perception and action. Oxford University Press, Oxford, pp. 9-54]) conflict resolution in both tasks results in the activation of different task-specific regions probably related to the different sources of task-irrelevant information. Furthermore, the present data give evidence those task-specific regions are most likely to detect the relationship between task-relevant and task-irrelevant information.

Adult↗
PubMed2006

Nicotine Stroop and addiction memory--an ERP study.

Drug-related cues have been shown to take effects on behavioral performance and physiological parameters such as event-related brain potentials (ERPs). In the present study we obtained EEG data during a modified Stroop task and during a color matching task using smoking related and neutral words (nicotine Stroop) in smokers and non-smoking controls. We assumed that in smokers smoking-related word meanings would interfere with color matching, and that this should be reflected in an ERP activation pattern comparable to that induced by the Stroop task. In smokers and non-smokers the classic Stroop-related interference effect of longer reaction times in the incongruent condition could be observed. This interference effect in both groups was related to a late posterio-central relative negativity and a right frontal relative positivity in the incongruent compared to the congruent condition. The behavioral data in the color matching task (nicotine Stroop) derived from both groups did not show a comparable interference effect related to the use of drug-related words. However, in smokers the smoking-related words elicited ERP activation patterns comparable to those evoked by the Stroop interference task. The ERP results are discussed as possibly reflecting a modulation of color processing of smoking-related words in smokers. The results imply an interference, but also attention enhancing, effect of smoking-related words in smokers, which maybe associated with addiction memory and enhanced sensitivity for drug-cues. Therefore, the addiction memory driven interference effect might be counteracted by performance enhancement induced by the same nicotine cues.

Adult↗
PubMed2006

Rapid immunoassay for the determination of glial fibrillary acidic protein (GFAP) in serum.

BACKGROUND: This study was aimed to develop a sensitive and rapid assay for the determination of glial fibrillary acidic protein (GFAP) in serum and to evaluate the clinical applicability in serum samples from patients with acute stroke. METHODS: The two-site chemiluminometric immunoassay, intended to use in a near-patient setting with a single incubation step (20 min), was used to measure serum samples from healthy blood donors and from patients with brain injury and correlated to serum S100B levels. RESULTS: The GFAP assay covered a concentration range up to 18 microg/L with an analytical sensitivity of 0.014 microg/L. The intra-assay precision was 3.5% at 1.55 microg/L (n=20) and 4.1% at 0.39 microg/L (n=20). The inter-assay precision was 3.8% at 9.1 microg/L (n=10) and 10.3 % at 0.21 microg/L (n=9). Normal controls (n=46) showed non-detectable GFAP with a 99% upper limit of <0.04 microg/L. GFAP values were associated with progression and severity of the illness in acute stroke patients. CONCLUSIONS: We have developed an improved assay for the measurement of GFAP levels in serum. Serum GFAP is a potential marker for prognosis and outcome in patients with central nervous system disorders.

Acute Disease↗
PubMed2005

Theta and alpha oscillations reflect differences in memory strategy and visual discrimination performance in patients with Parkinson's disease.

The aim of the present study was to investigate alterations in brain oscillatory activity during transient intentional encoding of abstract novel shapes in patients with Parkinson's disease (PD). Combined time-frequency analyses of alpha and theta power revealed a clear dissociation between PD patients (N=10) and age-matched healthy controls (N=10). PD patients used sub-optimal stimulus encoding strategies for subsequent maintenance and recall, whereas the controls mainly used categorization processes. In contrast to controls, PD patients showed significantly less theta increase and upper alpha suppression at frontal locations and significant laterality of early posterior theta and lower-2 alpha oscillations at right posterior locations. These findings suggest that the fronto-striatal circuits participate in visual categorization processes. Furthermore, theta and alpha oscillations appear to be involved in mediating the integration processes in mnemonic networks underlying visual categorization.

Aged↗
PubMed2005

Incidental effects of emotional valence in single word processing: an fMRI study.

The present study aimed at identifying the neural responses associated with the incidental processing of the emotional valence of single words using event-related functional magnetic resonance imaging (fMRI). Twenty right-handed participants performed a visual lexical decision task, discriminating between nouns and orthographically and phonologically legal nonwords. Positive, neutral and negative word categories were matched for frequency, number and frequency of orthographic neighbors, number of letters and imageability. Response times and accuracy data differed significantly between positive and neutral, and positive and negative words respectively, thus, replicating the findings of a pilot study. Words showed distributed, mainly left hemisphere activations, indicating involvement of a neural network responsible for semantic word knowledge. The neuroimaging data further revealed areas in left orbitofrontal gyrus and bilateral inferior frontal gyrus with greater activation to emotional than to neutral words. These brain regions are known to be involved in processing semantic and emotional information. Furthermore, distinct activations associated with positive words were observed in bilateral middle temporal and superior frontal gyrus, known to support semantic retrieval, and a distributed network, namely anterior and posterior cingulate gyrus, lingual gyrus and hippocampus when comparing positive and negative words. The latter areas were previously associated with explicit and not incidental processing of the emotional meaning of words and emotional memory retrieval. Thus, the results are discussed in relation to models of processing semantic and episodic emotional information.

Adult↗
PubMed2004

Erythropoietin: novel approaches to neuroprotection in human brain disease.

With the increased life expectancy in western industrialized countries, the incidence and prevalence of brain diseases dramatically increased. Stroke and a wide spectrum of neuropsychiatric illnesses such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, traumatic head injury, and schizophrenia all lead to severe disability. However, targeted effective therapies for treatment of these diseases are lacking. Even more frustrating is the fact that we do not yet clearly understand the basic mechanisms underlying the disease processes in these conditions. We propose a hypothesis of loss of neuronal function via a final common deleterious pathway in this clinically very heterogeneous disease group. This review presents a novel neuroprotective concept for treatment of brain disease: Erythropoietin (EPO). EPO is a natural body-own-protein hormone that has been used for treatment of anemia for more than a decade. The neuroprotective approach using EPO in brain disease represents a totally new frontier. The "Göttingen EPO-stroke trial" represents the first effective use in man of a neuroprotective therapy in an acute brain disease while the experimental EPO therapy to combat cognitive decline in patients with schizophrenia will be introduced as an example of a neuroprotective strategy for a chronic brain disease.

Animals↗
PubMed2003

Brain derived proteins as markers of acute stroke: their relation to pathophysiology, outcome prediction and neuroprotective drug monitoring.

PURPOSE: Ischemic stroke is associated with a variety pathophysiological changes affecting both glial and neuronal brain tissue. These changes are mirrored in the release of specific proteins into peripheral blood. Neurone-specific enolase (NSE), protein S100B and glial fibrillary acidic protein (GFAP) are those proteins investigated most often as peripheral surrogate markers of brain damage after stroke in humans. METHODS AND RESULTS: In the present article we present data which show that the release patterns of neuronal and glial tissue derived proteins after acute stroke are associated with the neuroradiological and neurobehavioral consequences of ischemic brain lesions and, additionally, may be useful in short-term outcome prediction. Kinetics of protein serum concentrations, however, are highly dependent on subtype of stroke lesions and do not merely reflect the degree of brain damage. They rather express complex neuronal-glial interactions as a (patho-)physiological consequence of ischemic brain lesions. We further demonstrate that S100B release patterns do reflect successful neuroprotective drug treatment with recombinant human erythropoietin (EPO) in acute stroke patients. CONCLUSIONS: The analysis of poststroke serum concentrations of glial tissue derived proteins might be a promising strategy to monitor and evaluate neuroprotective approaches in stroke treatment.

Biomarkers↗
PubMed1999

Protein S-100B and neuron specific enolase as early neurobiochemical markers of the severity of traumatic brain injury.

The present study aimed at the predictive value of early release patterns of protein S-100B and neuron specific enolase (NSE) in patients with traumatic brain injury. We investigated 69 patients who were admitted to the Department of Neurosurgery following traumatic brain injury. Both NSE and S-100B serum concentrations during the first three days after admission were highly and significantly correlated with Glasgow Coma and Coma Remission Scale scores at the respective blood sampling times as well as 2 weeks later. Signs of intracranial pathology as evaluated by CCT or MRI scans showed no association with NSE or S-100B release patterns. Our data support the hypothesis that NSE and protein S-100B are useful and sensitive neurobiochemical markers for the early clinical outcome of traumatic brain injury.

Journal Article↗