Biomedical subjects

T Wächter

Publications and source records attributed to T Wächter.

6 recordsLinked to original sources

PubMed2005

The effect of subthalamic nucleus stimulation on kinaesthesia in Parkinson's disease.

BACKGROUND: Parkinson's disease is accompanied by deficits in passive motion and limb position sense. OBJECTIVE: To investigate whether deep brain stimulation of the subthalamic nucleus (STN-DBS) reverses these proprioceptive deficits. METHODS AND RESULTS: A passive movement task was applied to nine patients with Parkinson's disease and bilateral chronic STN-DBS and to seven controls. Thresholds for 75% correct responses were 0.9 degrees for controls, 2.5 degrees for Parkinson's disease patients when stimulation was OFF, and 2.0 degrees when stimulation was ON. CONCLUSIONS: STN-DBS improves kinaesthesic deficits in Parkinson's disease, but does not lead to a full recovery of proprioceptive function.

Adult↗

PubMed2004

Probability detection mechanisms and motor learning.

The automatic detection of patterns or regularities in the environment is central to certain forms of motor learning, which are largely procedural and implicit. The rules underlying the detection and use of probabilistic information in the perceptual-motor domain are largely unknown. We conducted two experiments involving a motor learning task with direct and crossed mapping of motor responses in which probabilities were present at the stimulus set level, the response set level, and at the level of stimulus-response (S-R) mapping. We manipulated only one level at a time, while controlling for the other two. The results show that probabilities were detected only when present at the S-R mapping and motor levels, but not at the perceptual one (experiment 1), unless the perceptual features have a dimensional overlap with the S-R mapping rule (experiment 2). The effects of probability detection were mostly facilitatory at the S-R mapping, both facilitatory and inhibitory at the perceptual level, and predominantly inhibitory at the response-set level. The facilitatory effects were based on learning the absolute frequencies first and transitional probabilities later (for the S-R mapping rule) or both types of information at the same time (for perceptual level), whereas the inhibitory effects were based on learning first the transitional probabilities. Our data suggest that both absolute frequencies and transitional probabilities are used in motor learning, but in different temporal orders, according to the probabilistic properties of the environment. The results support the idea that separate neural circuits may be involved in detecting absolute frequencies as compared to transitional probabilities.

Adolescent↗

PubMed2002

Steele-Richardson-Olszewski-syndrome: the relation of dopamine D2 receptor binding and subcortical lesions in MRI.

We compared (123)I-iodobenzamide single photon emission computed tomography (IBZM-SPECT) for imaging of striatal dopamine D(2) receptors in vivo, and MRI in 32 patients with the clinical diagnosis of progressive supranuclear palsy (PSP). We found a significant inter-dependence of reduction of specific striatal IBZM binding indicative of striatal degeneration and of the absence of multiple signal hyperintensities in MRI; age had no influence neither on IBZM binding nor on signal hyperintensities. We conclude that the presence of multiple signal hyperintensities should raise doubt on the correct clinical diagnosis.

Aged↗

PubMed2001

[Parkinson disease. Directed use of modern therapy].

The approval of new antiparkinsonian drugs such as novel dopamine agonists or COMT-inhibitors during the last years has improved the therapeutic possibilities in Parkinson's disease. The choice of the different drugs depends on their particular efficiency, their adverse effect profile, the stage of the disease, the cardinal symptoms, age, and comorbidity. Therefore the physician is challenged to adjust the therapeutic management of each patient to the particular medical and social needs. This article discusses the present therapeutic strategies for the different stages of the disease detailing the profile, the main applications and the most important side effects of each drug.

Antiparkinson Agents↗

PubMed2000

[Multimodal SPECT and MRT imaging data analysis for an improvement in the diagnosis of idiopathic Parkinson's syndrome].

Parkinson's disease (PD) is characterized by a degeneration of nigrostriatal dopaminergic neurons, which can be imaged with 123I-labeled 2 beta-carbomethoxy-3 beta-(4-iodophenyl) tropane ([123I]beta-CIT) and single-photon emission computed tomography (SPECT). However, the quality of the region of interest (ROI) technique used for quantitative analysis of SPECT data is compromised by limited anatomical information in the images. We investigated whether the diagnosis of PD can be improved by combining the use of SPECT images with morphological image data from magnetic resonance imaging (MRI)/computed tomography (CT). We examined 27 patients (8 men, 19 women; aged 55 +/- 13 years) with PD (Hoehn and Yahr stage 2.1 +/- 0.8) by high-resolution [123I]beta-CIT SPECT (185-200 MBq, Ceraspect camera). SPECT images were analyzed both by a unimodal technique (ROIs defined directly within the SPECT studies) and a multimodal technique (ROIs defined within individual MRI/CT studies and transferred to the corresponding interactively coregistered SPECT studies). [123I]beta-CIT binding ratios (cerebellum as reference), which were obtained for heads of caudate nuclei (CA), putamina (PU), and global striatal structures were compared with clinical parameters. Differences between contra- and ipsilateral (related to symptom dominance) striatal [123I]beta-CIT binding ratios proved to be larger in the multimodal ROI technique than in the unimodal approach (e.g., for PU: 1.2 vs. 0.7). Binding ratios obtained by the unimodal ROI technique were significantly correlated with those of the multimodal technique (e.g., for CA: y = 0.97x + 2.8; r = 0.70; P < 0.001). Concerning the correlations between SPECT data and clinical parameters, the significance levels in the multimodal ROI technique, for example, for the correlation between CA and the UPDRScom subscore (r = -0.49 vs. -0.32). These results show that the impact of [123I]beta-CIT SPECT for diagnosing PD is affected by the method used to analyze the SPECT images. The described multimodal approach, which is based on coregistration of SPECT and morphological imaging data, leads to improved determination of the degree of this dopaminergic disorder.

Adult↗

PubMed2000

Striatal [123I]beta-CIT SPECT and prefrontal cognitive functions in Parkinson's disease.

Twenty non-demented patients with idiopathic Parkinson's disease (PD) underwent single photon emission computed tomography (SPECT) with [123I]beta-CIT to further investigate the contribution of nigrostriatal dysfunction to cognitive and motor deficits. Compared to matched controls PD patients showed normal verbal intelligence, short-term memory and phasic alertness. There were significant (p < 0.05) deficits in tests of verbal working memory (digit ordering, reading span), strategic memory (story recall) and executive functions (card sorting), indicating a "prefrontal" cognitive deficit. Significant (p < 0.05) correlations were observed between dopamine transporter (DAT) density in the putamen and motor deficits as well as between DAT density in both striatal compartments (head of the caudate nucleus and putamen) and prefrontal functioning. Age was a major contributing factor to both cognitive status and nigrostriatal integrity as measured by [123I]beta-CIT SPECT. These results support the view that the striatum is part of a neuronal network that is mediating prefrontal cognitive functions.

Adult↗