László Balázs

Colonic sensitivity in irritable bowel syndrome and normal subjects according to their hemispheric preference and cognitive style.

According to our earlier results, non-painful, weak afferent visceral signals may exert a steady influence on brain processes, including cognitive functions. In the present series colonic impulses of irritable bowel syndrome (IBS) subjects served as a model of chronic impact from the gut. Hemispheric preference, as well as cognitive style of information processing served as indicators of covert changes in brain functions. In twentyone IBS patients and in ten control subjects of both sexes, the thresholds of minimal colonic distension sensitivity has been measured following the determination of hemispheric preference and of advantage in verbal or spatial information processing of the subjects. In IBS patients distension thresholds proved to be higher in verbals than in spatials, whereas in healthy controls the relationship of colonic thresholds and verbal versus, spatial advantage was reversed. Among the normal controls with left hemisphere preference a significantly higher distension threshold has been observed than in those with right hemisphere preference, whereas in the IBS group such threshold-differences were not observable.

Computer determination of systolic time intervals based on impedance cardiography

A computerized system has been developed based on impedance cardiography for processing systolic time intervals (STI) in psychophysiological experiments. The conventional method of STI determination is based on transducing three signals: electrocardiogram, phonocardiogram and pulse tracing (carotid pulse). Because of its negligible pulse transmission time the first derivative impedance cardiogram (dZ/dt) is more reliable than other pulse signals. Since the sharply demarcated points of the dZ/dt waveform occur simultaneously with the cardiac events the dZ/dt makes phonocardiogram processing unnecessary. Computer algorithms for STI assessment are based on processing two signals: the ECG and dZ/dt. The pre-ejection period (PEP), the left ventricular ejection time (LVET) and electromechanical systole (QS2) are derived by recognizing the B and X points on the dZ/dt signal as the endpoints of PEP and LVET respectively. X point identification consists of two steps: (i) the estimation of the QS2 based on the regression relationship between QS2 and heart rate (HR) and (ii) a filtering procedure for exact localization of the X point. The B point is determined by calculating the curvature function of the dZ/dt and employing a clustering procedure. The accuracy and reliability of the software were tested by processing data from 40 subjects under stress condition (cold pressor and mental arithmetic).

HEART RATE CONDITIONING EXPERIMENTS IN HUMANS

Publisher Summary This chapter discusses the heart rate (HR) conditioning experiments in humans. In the majority of experiments, histograms were shifted to the left relative to the control histograms constructed from the HR of intertrial intervals. Even when the differences between the means are similar, the frequency distributions can be different. For example, in some cases, the maximum does not shift significantly to the left and the disappearance of high frequencies is entirely responsible for the decrease in the mean. A fairly complex relationship seems to exist between certain combinations of personality traits and successful use of feedback. Susceptibility to hypnosis is not clearly related to the effectiveness of feedback. Similarly, no clear relationship was found between the vegetative type and the utilization of feedback either. However, the subjects who were able to slow their heart rates either with or without feedback, showed more sympathetic prevalence than a parasympathetic one.