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H Siebner

Publications and source records attributed to H Siebner.

At least 19 recordsLinked to original sources
PubMed2003

Effector-independent representations of simple and complex imagined finger movements: a combined fMRI and TMS study.

Kinesthetic motor imagery and actual execution of movements share a common neural circuitry. Functional magnetic resonance imaging was used in 12 right-handed volunteers to study brain activity during motor imagery and execution of simple and complex unimanual finger movements of the dominant and the nondominant hand. In the simple task, a flexible object was rhythmically compressed between thumb, index and middle finger. The complex task was a sequential finger-to-thumb opposition movement. Premotor, posterior parietal and cerebellar regions were significantly more active during motor imagery of complex movements than during mental rehearsal of the simple task. In 10 of the subjects, we also used transcranial magnetic brain stimulation to examine corticospinal excitability during the same motor imagery tasks. Motor-evoked potentials increased significantly over values obtained in a reference condition (visual imagery) during imagery of the complex, but not of the simple movement. Imagery of finger movements of either hand activated left dorsal and ventral premotor areas and the supplementary motor cortex regardless of task complexity. The effector-independent activation of left premotor areas was particularly evident in the simple motor imagery task and suggests a left hemispherical dominance for kinesthetic movement representations in right-handed subjects.

Adult↗
PubMed2001

Activation of frontal premotor areas during suprathreshold transcranial magnetic stimulation of the left primary sensorimotor cortex: a glucose metabolic PET study.

We employed cerebral (18)Fluoro-deoxyglucose positron emission tomography ([(18)F]FDG-PET) to visualize neuronal activation of the frontal motor and premotor cortex during suprathreshold repetitive transcranial magnetic stimulation (rTMS) applied to the left primary sensorimotor hand area (SM1(HAND)). Twelve right-handed normal subjects underwent two [(18)F]FDG-PET measurements at baseline without rTMS and during suprathreshold 2 Hz rTMS of the left SM1(HAND). In the rTMS condition, 1,800 magnetic stimuli at an intensity of 140% of motor-resting threshold were delivered immediately after intravenous injection of [(18)F]FDG. Relative differences in the normalized regional cerebral metabolic rate for glucose (rCMRglc) between the rTMS condition and baseline were determined using a voxel-by-voxel Student's t-test and a volume-of-interest analysis. Data analysis was a priori restricted to primary motor and premotor areas in the frontal cortex, namely the SM1, the supplementary motor area (SMA), the lateral premotor cortex (PMC), and the caudal anterior cingulate cortex (ACC) of either hemisphere. In addition to a relative increase in normalized rCMRglc in the stimulated SM1(HAND), suprathreshold rTMS was associated with well-localized increases in normalized rCMRglc in the caudal SMA and ACC on the medial wall of the frontal cortex and in the right precentral gyrus in the lateral PMC rostrally to the SM1. These data demonstrate that a selective activation of the SM1(HAND) is paralleled by an activation of a distinct set of remote premotor areas, suggesting a functional interaction between the primary motor and premotor cortex in humans.

Adult↗
PubMed2001

Central activation by histamine-induced itch: analogies to pain processing: a correlational analysis of O-15 H2O positron emission tomography studies.

The aim of this study was to identify the functional cerebral network involved in the central processing of itch and to detect analogies and differences to previously identified cerebral activation patterns triggered by painful noxious stimuli. Repeated positron emission tomography regional cerebral blood flow (rCBF) measurements using O15-labeled water were performed in six healthy right-handed male subjects (mean age 32 +/- 2 years). Each subject underwent 12 sequential rCBF measurements. In all subjects a standardized skin prick test was performed on the right forearm 2 min before each rCBF measurement. For activation, histamine was applied in nine tests in logarithmically increasing concentrations from 0.03 to 8%. Three tests were performed with isotonic saline solution serving as a control condition. Itch intensity and unpleasantness were registered with a visual analogue scale during each test. Subtraction analysis between activation and control conditions as well as correlation analysis with covariates were performed. Itch induced a significant activation in the predominantly contralateral somatosensory cortex and in the ipsilateral and contralateral motor areas (supplementary motor area (SMA), premotor cortex, primary motor cortex). Additional significant activations were found in the prefrontal cortex and the cingulate gyrus, but not in subcortical structures nor in the secondary somatosensory cortex. In correlation analyses, several cortical areas showed a graded increase in rCBF with the logarithm of the histamine concentration (bilateral sensorimotor areas and cingulate cortex; contralateral insula, superior temporal cortex and prefrontal cortex) and with itch unpleasantness (contralateral sensorimotor cortex, prefrontal cortex and posterior insula; ipsilateral SMA). Induction of itch results in the activation of a distributed cerebral network. Itch and pain seem to share common pathways (a medial and a lateral processing pathway and a strong projection to the motor system). In contrast to pain activation studies, no subcortical (i.e. thalamic) activations were detected and correlation analyses suggest differences in subjective processing of the two sensations.

Adult↗
PubMed1976

[Five years treatment of advanced solid malignomas with a combination of four cytostatic drugs (author's transl)].

132 patients with advanced solid malignomas were treated with a combination of four cytostatic drugs (vinblastine, amethopterine, 5-fluorouracil and cyclophosphamid) given on one day. This was repeated once every 2-3 weeks. In every case the diagnosis was made histologically and the tumour was staged according to the TNM-system. The treatment of breast and ovarian cancer brought the best results, improved by a synchronisation therapy. Good results were achieved also in the treatment of special kind of sarcomas and of carcinoma of the urine bladder. The general condition of patients with colon carcinoma could be improved in about 30%. Only one patient died by drug-induced pancytopenia, otherwise severe side-effects were not noted. Before beginning the therapy the cell-mediated immunity of 31 patients was tested by skin-tests with tuberkulin purified protein derivative (PPD) and dinitrochlorbenzole (DNCB). Before and during cytostatic therapy PPD reactions were proven by 23 patients. In accordance to other authors we found that cell-mediated immunity is decreased in the advanced stage of malignoma. Further we noted that delayed hypersensitivity and the number of lymphocytes and monocytes in peripherel blood are important to prognosis and course in patients with cancer.

Adult↗