[Diagnostic methods for Helicobacter pylori infection in children]. / Diagnostiek naar Helicobacter pylori-infectie bij kinderen.

A Helicobacter pylori infection is usually acquired during early childhood. Poor socioeconomic circumstances form an important risk factor for this. An untreated infection may lead to peptic ulceration and, particularly in adults, to gastric cancer and mucosa associated lymphoid tissue (MALT) lymphoma. The gold standard for the diagnosis of H. pylori infection is gastroscopy with histology and culture of biopsy specimens. Non-invasive tests are serology, 13C-urea breath test and stool antigen test. The sensitivity and specificity of serology tests are low in children, but for both the 13C-urea breath test and the stool antigen test the sensitivity and specificity are high. A 'test and treat' approach is advised with due consideration for possible symptoms and the risk for peptic ulcers and gastric cancer at a more advanced age. The treatment results must be evaluated. If necessary, young children can be treated at a later age.

Cortical activation, signal-to-noise ratio and stochastic resonance during information processing in man.

OBJECTIVES: The goal of this study was to determine the relation between EEG, event-related potentials and information processing as measured by an acoustical choice reaction time task. In particular, we wanted to find out to what extent reaction-time performance is related to the pre-stimulus EEG activity (frequency domain) and the magnitude of signal power as well as noise power (stimulus-uncorrelated activity) after the tones (time domain). MATERIALS AND METHODS: For parametrization, EEG-activity was factorized across pre-defined frequency bands and 19 electrode positions, applying spectral power and coherence analysis. Signal power was estimated by calculating the mean power of the evoked single sweeps. Noise power was computed by subtracting the latter minus the power of the average evoked potential. We investigated 254 healthy subjects who had to perform an acoustical choice reaction task during running EEG. RESULTS: In the frequency domain, it was found that high frontally pronounced delta-power in the pre-stimulus EEG correlates with fast reaction-time performance, which was regarded as the expression of a readiness potential in the frequency domain, reflecting increased cortical activation. In the time domain, fast reaction times were found to be correlated with the amplitude of the event-related potential N100 as well as with the signal power and signal-to-noise ratio of the evoked activity. This result pointed to the frequently described relation between evoked signals and information processing. In accordance with the theory of stochastic resonance, we also found a positive correlation between the magnitude of noise power after the stimulus and reaction-time performance. Besides, noise power was found to be positively correlated with pre-stimulus cortical activation (mainly in the delta and alphal frequency band), whereas no relation was found between pre-stimulus EEG and the signal power of the event-related activity, except for a weak relation to the alpha2 power. CONCLUSION: Our findings support the notion that information processing is not only dependent on signal strength but also on a certain amount of basic noise, reflecting the overall energy state of the brain.