Biomedical subjects

H Hautzel

Publications and source records attributed to H Hautzel.

10 recordsLinked to original sources

PubMed2004

When planning fails: individual differences and error-related brain activity in problem solving.

The neuronal processes underlying correct and erroneous problem solving were studied in strong and weak problem-solvers using functional magnetic resonance imaging (fMRI). During planning, the right dorsolateral prefrontal cortex was activated, and showed a linear relationship with the participants' performance level. A similar pattern emerged in right inferior parietal regions for all trials, and in anterior cingulate cortex for erroneously solved trials only. In the performance phase, when the pre-planned moves had to be executed by means of an fMRI-compatible computer mouse, the right dorsolateral prefrontal cortex was again activated jointly with right parahippocampal cortex, and displayed a similar positive relationship with the participants' performance level. Incorrectly solved problems elicited stronger bilateral prefrontal and left inferior parietal activations than correctly solved trials. For both individual ability and trial-specific performance, our results thus demonstrate the crucial involvement of right prefrontal cortex in efficient visuospatial planning.

Adult↗

PubMed2004

Depression and anxiety in different thyroid function states.

Previous studies on hypothyroid subjects have indicated serious psychiatric symptoms affecting the patients' quality of life. The present prospective cross-sectional study's aim was to examine these symptoms in thyroid patients with different functional states. A total of 254 patients (age: 56 +/- 14 years [mean +/- standard deviation], 181 female, 73 male) referred to a hospital for radioiodine treatment of hyperthyroidism or for follow-up of differentiated thyroid cancer, respectively, were included. All patients underwent the twelve-item general health questionnaire, which is an instrument for detecting mood disturbances. Euthyroid and hyperthyroid patients did not differ significantly in their general health questionnaire score (11 +/- 5 vs. 11 +/- 7), nor did subclinical hyperthyroid (11 +/- 6) or subclinical hypothyroid subjects (12 +/- 5). In contrast, hypothyroid patients showed a significantly higher mean score (17 +/- 7, p < 0.001, ANOVA). Binary logistic regression revealed that hypothyroidism increases age and gender-adjusted risk for critical mood deterioration by seven-fold. Thus, hypothyroidism represents a widely underestimated functional condition that may severely affect mental health.

Adult↗

PubMed2003

[Neurocognition and PET. Strategies for data analysis in activation studies on working memory].

AIM: In cognitive neuroscience regional cerebral blood flow (rCBF) imaging with positron-emission-tomography (PET) is a powerful tool to characterize different aspects of cognitive processes by using different data analysis approaches. By use of an n-back verbal working memory task (varied from 0- to 3-back) we present cognitive subtraction analysis as basic strategy as well as parametric and covariance analyses and discuss the results. METHODS: Correlation analyses were performed using the individual performance rate as an external covariate, computing inter-regional correlations, and as network analysis applying structural equation modelling to evaluate the effective connectivity between the involved brain regions. RESULTS: Subtraction analyses revealed a fronto-parietal neuronal network also including the anterior cingulate cortex and the cerebellum. With higher memory load the parametric analysis evidenced linear rCBF increases in prefrontal, pre-motor and inferior parietal areas including the precuneus as well as in the anterior cingulate cortex. The rCBF correlation with the individual performance as external covariate depicted negative correlations in bilateral prefrontal and inferior parietal regions, in the precuneus and the anterior cingulate cortex. The network analysis demonstrated mainly occipito-frontally directed interactions which were predominantly left-hemispheric. Additionally, strong linkages were found between extrastriate and parietal regions as well as within the parietal cortex. CONCLUSION: The data analysis approaches presented here contribute to an extended and more elaborated understanding of cognitive processes and their different sub-aspects.

Brain↗

PubMed2002

Topographic segregation and convergence of verbal, object, shape and spatial working memory in humans.

This functional magnetic resonance imaging study investigates commonalties and differences in working memory (WM) processes employing different types of stimuli. We specifically sought to characterize topographic convergence and segregation with respect to prefrontal cortex involvement using verbal, spatial, real object and shape memory items in a two-back WM task. Both the dorsolateral and ventrolateral prefrontal cortices are conjointly activated across all stimulus types. No stimulus-specific differences in the activation patterns of the prefrontal cortex could be demonstrated giving support to the view of an amodal prefrontal involvement during WM processes. However, extra-frontal regions specialized on feature processing and involved in the preprocessing of the stimuli were selectively activated by these different subtypes of WM. These selectively activated regions are assigned to parts of the ventral and dorsal stream.

Adult↗

PubMed2002

[The (11C) acetate positron emission tomography in prostatic carcinoma. New prospects in metabolic imaging].

The exact staging of prostate cancer is mandatory to allow selection of the appropriate primary therapy. In addition, if the PSA level rises again it is extremely important to find the site(s) of local recurrence or metastatic spread as soon as possible. However, with the morphological and metabolic imaging techniques currently available it is often not possible to answer these questions with adequate sensitivity and specificity, since small metastases < or = 1 cm in diameter are likely to remain undetected by them. In the last few years new radioactive labelled tracers have been introduced for use in positron emission tomography (PET), and it is hoped that the shortcomings in the diagnostic procedures used for prostate carcinoma might be compensated by their use. Besides 11C- or 18F-labelled choline, [11C]Acetate is also attracting attention as a promising PET tracer. In this paper we review the various PET tracers available and evaluate the advantages and the drawbacks of [11C]Acetate in three case studies by comparing [11C]Acetate-PET with histology and with other imaging techniques. The use of [11C]Acetate appears to be feasible and helpful in the diagnosis of prostate carcinoma. However, its final value relative to other imaging techniques needs further investigation, with special reference to initial lymph node involvement, early localisation of recurrence and possible noninvasive differentiation between prostate cancer, prostatis and benign hyperplasia of the prostate.

Acetates↗

PubMed2001

The motion aftereffect: more than area V5/MT? Evidence from 15O-butanol PET studies.

The motion aftereffect is a perceptual phenomenon which has been extensively investigated both psychologically and physiologically. Neuroimaging techniques have recently demonstrated that area V5/MT is activated during the perception of this illusion. The aim of this study was to test the hypothesis if a more broadly distributed network of brain regions subserves the motion aftereffect. To identify the neuronal structures involved in the perception of the motion aftereffect, regional cerebral blood flow (rCBF) measurements with positron emission tomography were performed in six normal volunteers. Data were analysed using SPM96. The motion-sensitive visual areas including area V5/MT were activated in both hemispheres. Additionally, the lateral parietal cortex bilaterally, the right dorsolateral prefrontal cortex, the anterior cingulate cortex and the left cerebellum showed significant increases in rCBF values during the experience of the waterfall illusion. In a further reference condition with identical attentional demand but no perception of a motion aftereffect elevated rCBF were found in these regions as well. In conclusion, our findings support the notion that the perceptual illusion of motion arises exclusively in the motion-sensitive visual area V5/MT. In addition, a more widespread network of brain regions including the prefrontal and parietal cortex is activated during the waterfall illusion which represents a non-motion aftereffect-specific subset of brain areas but is involved in more basic attentional processing and cognition.

Adult↗

PubMed2000

Transport mechanisms of 3-[123I]iodo-alpha-methyl-L-tyrosine in a human glioma cell line: comparison with [3H]methyl]-L-methionine.

UNLABELLED: The amino acid analog 3-[(123)I]iodo-alpha-methyl-L-tyrosine (IMT) is under clinical evaluation as a SPECT tracer of amino acid transport in brain tumors. This study investigated the carrier systems involved in IMT transport in human glioma cells in comparison with [3H-methyl]-L-methionine (3H-MET). METHODS: Human glioma cells, type 86HG-39, were cultured and incubated for 1 min at 37 degrees C with IMT and 3H-MET in the lag phase (1.2 d after seeding), exponential growth phase (3 d after seeding), and plateau phase (8 d after seeding). Experiments were performed in the presence and absence of Na+, during inhibition of system L amino acid transport by 2-aminobicyclo[2.2.1 ]heptane-2-carboxylic acid (BCH), and during inhibition of system A amino acid transport by 2-(methylamino)-isobutyric acid (MeAIB). RESULTS: IMT and 3H-MET uptake decreased by 55%-73% when the cells entered from the exponential growth phase into the plateau phase (P< 0.05; n = 3-11). Inhibition by BCH reduced uptake of IMT in the lag phase, exponential growth phase, and plateau phase by 90%-98% (P < 0.001; n = 3-6) and the uptake of 3H-MET by 73%-83% (P < 0.001; n = 3-11). In a Na+-free medium 3H-MET uptake was reduced by 23%-33% (P < 0.05; n = 3-11), whereas IMT uptake was not significantly different. MeAIB showed no significant effect on IMT or 3H-MET uptake in either phase. CONCLUSION: Transport of both IMT and 3H-MET depends on the proliferation rate of human glioma cells in vitro and is dominated by BCH-sensitive transport. These data indicate that system L is induced in rapidly proliferating glioma cells and is the main contributor to the uptake of both tracers. 3H-MET transport showed a minor Na+ dependency that was not attributable to system A. The similarity of transport mechanisms of both tracers emphasizes the clinical equivalence of IMT SPECT and (11)C-MET PET for the diagnostic evaluation of gliomas.

Amino Acids↗

PubMed2000

[Comparison of PET and fMRI activation patterns durnig declarative memory processes].

AIM: In this study neuronal correlates of encoding and retrieval in paired association learning were compared using two different neuroimaging methods: positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). METHODS: 6 right-handed normal male volunteers took part in the study. Each subject underwent six 0-15-butanol PET scans and on fMRI study comprising four single epochs on a different day. The subjects had to learn and retrieve 12 word pairs which were visually presented (highly imaginable words, not semantically related). RESULTS: Mean recall accuracy was 93% in the PET as well as in the fMRI experiment. During encoding and retrieval we found anterior cingulate cortex activation, and bilateral prefrontal cortex activation in both imaging modalities. Furthermore, we demonstrate the importance of the precuneus in episodic memory. With PET the results demonstrate frontopolar activations whereas fMRI fails to show activations in this area probably due to susceptibility artifacts. In fMRI we found additionally parahippocampal activation and due to the whole-brain coverage cerebellar activation during encoding. The distance between the center-of-mass activations in both modalities was 7.2 +/- 6.5 mm. CONCLUSION: There is a preponderance of commonalities in the activation patterns yielded with fMRI and PET. However, there are also important differences. The decision to choose one or the other neuroimaging modality should among other aspects depend on the study design (single subject vs. group study) and the task of interest.

Adult↗

PubMed1997

Early changes in fluorine-18-FDG uptake during radiotherapy.

UNLABELLED: The aim of this case study was to quantify metabolic changes in tumor tissue during and directly after external radiotherapy. METHODS: We performed six FDG-PET scans of the neck in a patient with two lymph node metastases of a papillary thyroid carcinoma and an antigranulocyte antibody scintigraphy of the same region to assess the inflammatory reaction. RESULTS: The FDG-PET scans show an initial increase of tracer uptake in both metastases after application of 6 Gy followed by a slow but constant decline with increasing radiation dose. In the deep metastasis the FDG uptake returned to the initial level after 30 Gy total dose whereas the metabolic activity in the superficial lymph node remained high, even after 60 Gy total dose. The antigranulocyte scan demonstrated an intense inflammation in the latter metastasis. CONCLUSION: There is an initial enhancement in metabolism induced by irradiation which is measureable by FDG-PET. With increasing dose, the metabolic activity declines constantly. The additional inflammatory reaction might contribute to the glucose uptake in irradiated tumors.

Aged↗

PubMedDate not supplied

Imaging and neural modelling in episodic and working memory processes.

Neuroimaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have revealed the involvement of distributed brain regions in memory processes mainly by the use of subtraction strategy based data analyses. Covariance analysis based data analysis strategies have been introduced more recently which allow functional interactions between brain regions of a neuronal network to be assessed. This contribution focuses on studies aiming to (1) establish the functional topography of episodic and working memory processes in young and old normal volunteers, (2) to assess functional interactions between modules of networks of brain regions by means of covariance based analyses and systems level modelling, (3) to characterise the temporal dynamics by the use of magnetoencephalography (MEG) and (4) to relate neuroimaging data to the underpinning neural networks. Male normal young and old volunteers without neurological or psychiatric illness participated in neuroimaging studies (PET, fMRI, MEG). Studies were approved by the ethical committee and federal authorities. Our results in young volunteers show distributed brain areas that are involved in memory processes (episodic and working memory) and show much of an overlap with respect to the network components. Systems level modelling analyses support the hypothesis of bihemispheric, asymmetric networks subserving memory processes and revealed both similarities in general and differences in the interactions between brain regions during episodic encoding and retrieval as well as working memory. Changes in memory function with ageing are evident from functional topographic studies in old volunteers activating more brain regions as compared to young volunteers. There are more and stronger influences of prefrontal regions in elderly volunteers comparing the functional models between old and young subjects. We discuss the way that the systems level models of the PET and fMRI results have implications for the underlying neural network functioning of the brain. This is done by developing simplifying assumptions, which lead from the equations describing the activities of the coupled neural modules to the systems level model equations. The resulting implications for the neural interactions are then discussed, in terms of a set of synaptically coupled neural modules. Finally, we consider how a similar analysis could be extended from the spatial to the temporal domain thus including the EEG and MEG results. The implication of preliminary MEG results presented here for the temporality arising in the interaction between the coupled neural modules in a working memory paradigm is discussed in terms of the previously developed neural network models arising from the PET and fMRI data.

Adult↗