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W Stadler

Publications and source records attributed to W Stadler.

16 recordsLinked to original sources
PubMed2005

Intelligence related differences in EEG-bandpower.

Several studies on the relationship between event-related desynchronization/synchronization (ERD/ERS) and cognitive performance revealed contradictory results particularly for the alpha band. Studies from our laboratory have shown that good performers show a larger upper alpha ERD (interpreted in terms of larger cortical activation) than bad performers. In contrast, other researchers found evidence for the neural efficiency hypothesis, which states that more intelligent subjects exhibit a smaller extent of cortical activation, which is assumed to be reflected by a smaller upper alpha ERD. Here we address the question whether these divergent results may be due to differences in general task difficulty. Using a modified version of the RAVEN, individually divided into easy and difficult tasks, a group of average and a group of highly intelligent subjects (IQ- and IQ+) have been investigated. While in the theta frequency IQ+ subjects generally exhibited a significantly stronger activation, we found a significant interaction of task difficulty and IQ group in the upper alpha band, indicating both, a weaker activation for the high IQ group during the easy tasks, and a significant increase from easy to difficult tasks for IQ+ only.

Adolescent↗
PubMed2005

A shift of visual spatial attention is selectively associated with human EEG alpha activity.

Event-related potentials and ongoing oscillatory electroencephalogram (EEG) activity were measured while subjects performed a cued visual spatial attention task. They were instructed to shift their attention to either the left or right visual hemifield according to a cue, which could be valid or invalid. Thereafter, a peripheral target had to be evaluated. At posterior parietal brain areas early components of the event-related potential (P1 and N1) were higher when the cue had been valid compared with invalid. An anticipatory attention effect was found in EEG alpha magnitude at parieto-occipital electrode sites. Starting 200 ms before target onset alpha amplitudes were significantly stronger suppressed at sites contralateral to the attended visual hemifield than ipsilateral to it. In addition, phase coupling between prefrontal and posterior parietal electrode sites was calculated. It was found that prefrontal cortex shows stronger phase coupling with posterior sites that are contralateral to the attended hemifield than ipsilateral sites. The results suggest that a shift of attention selectively modulates excitability of the contralateral posterior parietal cortex and that this posterior modulation of alpha activity is controlled by prefrontal regions.

Adult↗
PubMed2002

The interplay between theta and alpha oscillations in the human electroencephalogram reflects the transfer of information between memory systems.

The exchange of information between the working and long-term memory system (WMS and LTMS) was investigated. We analyzed evoked theta and upper alpha desynchronization in a special memory task, designed to study the transfer of information between both memory systems. The results show that during attempts to retrieve information from the LTMS, evoked theta oscillations spread from anterior to posterior recording sites. When information actually is retrieved, the direction reverses and theta spreads to frontal sites. This time point--when direction reverses--varies between subjects to a large extent but is significantly correlated with memory performance and the onset of upper alpha desynchronization. We conclude that this phenomenon reflects the transfer of information between the WMS and LTMS

Adult↗
PubMed2001

Episodic retrieval is reflected by a process specific increase in human electroencephalographic theta activity.

Is an increase in theta during retrieval due (primarily) to the access of a stored code or to more general processes? The electroencephalogram was recorded while subjects performed a recognition task with pictures. According to the event-related desynchronization/synchronization method, the percentage of band power changes was calculated during encoding and retrieval for a theta and three alpha bands. Significant results were obtained (with minor exceptions) only in the theta band. The increase in theta was significantly larger during retrieval than during encoding but did not differ significantly between new and successfully retrieved old pictures. Because a memory trace is lacking for new pictures, the increase in theta during retrieval reflects primarily general processing demands of a complex episodic memory system.

Adult↗
PubMed2000

Simultaneous desynchronization and synchronization of different alpha responses in the human electroencephalograph: a neglected paradox?

This study aims to resolve a paradox. Experiments measuring alpha band power report an event related decrease (desynchronization) in alpha activity, whereas those measuring evoked alpha report synchronization. During a recognition memory task with human subjects, we measured the evoked (phase locked) and induced (not phase locked) alpha response. The findings reveal that evoked alpha is due to a transient phase locking (at about 100-200 ms poststimulus) of three alpha sub-bands which can be observed only at parieto-occipital sites. In contrast, induced alpha shows a widespread pattern of desynchronization at most recording sites. Thus, opposite alpha responses occur within similar time windows. Evoked alpha synchronization may reflect cortical inhibition which serves to increase the signal to noise ratio for activation processes following immediately later.

Adolescent↗
PubMed2000

The time locked theta response reflects interindividual differences in human memory performance.

Recent research indicates that an increase in theta band power is related to episodic memory performance. In this study with human subjects, the evoked (time locked) and induced (not time locked) theta response is analyzed in a recognition task. The results show a strong evoked theta response during an early retrieval period of up to 400 ms. Only for good memory performers theta is strictly time locked, indicating that theta peaks appear in preferred time windows after a target is presented. This effect--which coincides with a large P3--suggests that good performance requires a strict timing of different processing stages that correspond to cycles of theta activity.

Adult↗
PubMed2000

Phase II trial of gemcitabine plus cisplatin in patients with metastatic urothelial cancer.

PURPOSE: To assess the activity and toxicity of the combination of gemcitabine and cisplatin in the treatment of chemotherapy-naive patients with metastatic urothelial cancer. PATIENTS AND METHODS: Forty-six patients with measurable stage IV carcinoma of the urothelium were enrolled onto this trial. Gemcitabine 1,000 mg/m(2) was administered intravenously for 30 to 60 minutes on days 1, 8, and 15 of each 28-day cycle. Cisplatin was administered after gemcitabine on day 1 of each cycle. The first 11 patients received an initial cisplatin dose of 100 mg/m(2). Due to the hematologic toxicity observed in several of these patients, the dose was reduced to 75 mg/m(2) in the remaining 35 patients. Patients were treated with six cycles, unless disease progression or severe toxicity necessitated earlier discontinuation. RESULTS: Ten of the 46 patients achieved a complete response and nine showed a partial response. The overall response rate was 41%. The median time to treatment failure was 5.5 months. The median survival was 14.3 months, and the 1-year survival probability was 54%. Most of the toxicities were hematologic and, in general, easily manageable. CONCLUSION: Gemcitabine plus cisplatin is active in the treatment of metastatic urothelial cancer in chemotherapy-naive patients and has an acceptable clinical safety profile. Studies are under way to further define the place of gemcitabine in combination with other chemotherapeutic agents in the treatment of metastatic urothelial cancer.

Adult↗
PubMed1995

Increased p16 levels correlate with pRb alterations in human urothelial cells.

The CDKN2 (MTS1) gene is located at 9p21; its product, p16, inhibits the cyclin D/CDK4 complex that phosphorylates pRb, thus negatively regulating cell cycle progression [M. Serrano et al., Nature (Lond.), 366: 704, 1994; A. Kamb et al., Science (Washington DC), 264: 436, 1994; T. Nobori et al., Nature (Lond.), 368: 753, 1994]. CDKN2 mutations are more common in cultured human uroepithelial cells (HUC) than in uncultured bladder cancers. We examined the status of CDKN2/p16 in early and late passage (P) cultures of HUC. HUC immortalization was not accompanied by p16 loss, even in cells with a hemizygous 9p21-pter deletion, but late passage cultures with a p16 loss showed decreased generation time. Thus, the data do not indicate that CDKN2 is a candidate for a chromosome 9 senescence gene but suggest that p16 loss may confer a growth advantage in vitro. Significant differences in p16 levels were observed among HUC cell lines, but no CDKN2 mutations were detected. However, an inverse correlation between elevated p16 and loss of pRb function was observed (P < 10(-4)). Ten samples with normal pRb showed low or undetectable p16 levels, while seven samples with known pRb alterations showed abundant p16 but nevertheless grew vigorously in culture. These results support the hypothesis that p16 mediated cell cycle inhibition, as well as p16 regulation, occurs via pRb dependent pathway(s).

Base Sequence↗
PubMed1988

[Changes in the treatment of urogenital tuberculosis].

Potent antituberculosis drugs and new endourological measures have changed the concept of management of urogenital tuberculosis. This paper presents a report on 56 patients treated with rifampicin, ethambutol and isoniazid for 1 year. Therapy was started in hospital and continued on an ambulatory basis. Reconstructive surgery was carried out as early as 4-5 weeks after commencement of therapy, whereby only destroyed organs wee removed. Follow up continued at three-monthly intervals for a period of 2-5 years after completion of chemotherapy. All patients were cured.

Adolescent↗
PubMed1981

Tuberculosis of the pancreas.

In a case report, the rate condition of tuberculosis of the pancreas is described. There are two conceivable ways in which the pancreas may become diseased: 1. toxic-allergic reaction of the pancreas in response to generalized tuberculosis (so-called concomitant pancreatis) 2. Invasion of the pancreas by tubercle bacteria disseminated via the blood, or through penetration of the organ by adjacent caseating abdominal lymph nodes. Histologically, epithelioid cells and Langhans' giant cells are only rarely found; caseation usually develops, with subsequent calcification, which can lead to stenosis of the pancreatic duct. In patients with generalized tuberculosis and abdominal complaints, the diagnosis is most reliably established on the basis of ERCP and CAT. In the presence of pain, resection of the affected portion of the pancreas may be considered as means of treatment.

Cholangiopancreatography, Endoscopic Retrograde↗