Helmut K. Lackner

Magnetic induction tomography: hardware for multi-frequency measurements in biological tissues.

Magnetic induction tomography (MIT) is a contactless method for mapping the electrical conductivity of tissue. MIT is based on the perturbation of an alternating magnetic field by a conducting object. The perturbation is detected by a voltage change in a receivercoil. At physiologically interesting frequencies (10 kHz-10 MHz) and conductivities (< 2 S m(-1)) the lower limit for the relative voltage change (signal/carrier ratio = SCR) to be resolved is 10(-7)-10(-10). A new MIT hardware has been developed consisting of a coil system with planar gradiometers and a high-resolution phase detector (PD). The gradiometer together with the PD resolves an SCR of 2.5 x 10(-5) (SNR = 20 dB at 150 kHz, acquisition speed: 100 ms). The system operates between 20 and 370 kHz with the possibility of extending the range up to 1 MHz. The feasibility of measuring conductivity spectra in the beta-dispersion range of biological tissues is experimentally demonstrated. An improvement of the resolution towards SCR = 10(-7) with an SNR of > or = 20 dB at frequencies > 100 kHz is possible. On-line spectroscopy of tissue conductivity with low spatial resolution appears feasible, thus enabling applications such as non-invasive monitoring of brain oedema.

Trait and state positive affect and cardiovascular recovery from experimental academic stress

As compared to negative affect, only a small number of studies have examined influences of positive affect on cardiovascular stress responses, of which only a few were concerned with cardiovascular recovery. In this study, heart rate, low- and high-frequency heart rate variability, blood pressure, and levels of subjectively experienced stress were obtained in 65 students before, during and after exposure to academic stress in an ecologically valid setting. Higher trait positive affect was associated with more complete cardiovascular and subjective post-stress recovery. This effect was independent of negative affect and of affective state during anticipation of the stressor. In contrast, a more positive affective state during anticipation of the challenge was related to poor post-stress recovery. The findings suggest that a temporally stable positive affect disposition may be related to adaptive responses, whereas positive emotional states in the context of stressful events can also contribute to prolonged post-stress recovery.

Prefrontal EEG alpha asymmetry changes while observing disaster happening to other people: Cardiac correlates and prediction of emotional impact

Changes of EEG alpha asymmetry in terms of increased right versus left sided activity in prefrontal cortex are considered to index activation of the withdrawal/avoidance motivational system. The present study aimed to add evidence of the validity of individual differences in the EEG alpha asymmetry response and their relevance regarding the impact of emotional events. The magnitude of the EEG alpha asymmetry response while watching a film consisting of scenes of real injury and death correlated with components of transient cardiac responses to sudden horrifying events happening to persons in the film which index withdrawal/avoidance motivation and heightened attention and perceptual intake. Additionally, it predicted greater mood deterioration following the film and film-related intrusive memories and avoidance over the following week. The study provides further evidence for prefrontal EEG alpha asymmetry changes in response to relevant stimuli reflecting an individuals sensitivity to negative social-emotional cues encountered in everyday life.

I got it! Transient cardiovascular response to the perception of humor

The aim of the present study was to examine the transient cardiovascular response to the perception of humor, that is, the impact of the cognitive process of insight as well as the modulation of the response by the affective appraisal of the humor. To this end transient heart rate, stroke volume, cardiac output, and blood pressure responses were obtained in the immediate context of detecting the punch line in cartoons. Fine-grained analysis of the transient behavior of cardiovascular variables during viewing the cartoons was contrasted to non-humorous cartoon-like pictures. The detection of a punch line was accompanied by relative heart rate acceleration in conjunction with increased cardiac output, which was more pronounced the more amusing the cartoons were perceived. These results provide first evidence of the usefulness of cardiovascular variables for detecting the moment of insight and the quantification of the size of the emotional response accompanying it.

Association Between Superficial Vein Thrombosis and Deep Vein Thrombosis of the Lower Extremities

OBJECTIVE To evaluate the occurrence of deep vein thrombosis (DVT) in patients with superficial vein thrombosis (SVT). DESIGN A prospective study in patients with sonographically proven SVT. SETTING Outpatient department of the Department of Dermatology, Medical University of Graz. Patients Forty-six consecutive patients with superficial vein thrombosis were enrolled. Intervention Every patient underwent color-coded duplex sonography of both lower extremities at the beginning of the study. MAIN OUTCOME MEASURES Important risk factors (eg, history of thromboembolic events, recent immobilization, active malignant disease, and the use of oral contraceptives) were investigated. RESULTS In 24% of our patients, a concomitant, mostly asymptomatic DVT was found. In 73% of these patients, the DVT occurred in the affected leg, in 9% in the contralateral leg, and in 18% in both legs. The calf muscle veins were most commonly involved. In all patients with DVT, the SVT was located on the lower leg and the D-dimer findings were positive. CONCLUSIONS Superficial vein thrombosis is not a life-threatening disease, but the risk of concomitant DVT cannot be ignored. Color-coded duplex sonography should be performed in patients with SVT to rule out DVT.

The effects of emotion regulation on the desire to overeat in restrained eaters

The aim of the present study was to test whether emotion regulation (ER) strategies are underlying processes in the link between negative emotions and the desire to overeat (DTE) in high restrained eaters (HR). Forty-eight female HR and 46 female low restrained eaters (LR) watched three sadness inducing film clips. Thereby, participants were randomly assigned to and trained in one of three conditions while watching the first two clips: to suppress upcoming emotions, to accept upcoming emotions or to reappraise the situation. After that, they participated in an experiment in which the learned ER strategy was implemented while watching the third sadness inducing film clip. DTE and sadness were assessed prior to and at the end of each clip. Additionally, physiological measures of the sympathetic and parasympathetic branch were obtained. In the HR group emotion acceptance and suppression lead to a significant increase of the DTE from baseline to post-film, while there was no change in DTE in the reappraisal condition. However, psychophysiological measures were not moderated by ER strategies. The results are discussed in terms of the limited resource model.

Melanoma Markers in Marathon Runners: Increase with Sun Exposure and Physical Strain

Background: Marathon runners seem to have an increased melanoma risk. Objective: To identify potential melanoma markers. Methods: 150 marathon runners volunteered to take part in the skin cancer screening campaign. After the runners completed a questionnaire about melanoma risk factors, types of sportswear and training programs, they received a total skin examination. The number of lentigines and nevi on the left shoulder and the left buttock were counted in each participant using templates in standardized positions. The potential association of training sportswear and training parameters with the number of lentigines and nevi on the left shoulder was evaluated. Results: The mean number of lentigines on the left shoulder was 19.6 ± 18.2 (SD), whereas no lentigines were found on the left buttock (p = 0.000). The number of nevi also differed significantly between the 2 localizations with higher numbers on the left shoulder (p = 0.000). While lifetime sunburn history and type of sportswear correlated with the number of lentigines, training parameters had an impact on the number of nevi. Independent of their mean weekly running time, runners with higher heart rates while training, higher training velocities and higher physical strain indexes showed more nevi on the shoulder than the other runners (p = 0.029, 0.046, 0.038, respectively). Conclusion: Sun exposure and high physical strain lead to an increase in melanoma markers such as lentigines and nevi in marathon runners.

Hormonal and plasma volume changes after presyncope

Eur J Clin Invest 2011; 41 (11): 1180–1185

Time course of cardiovascular responses induced by mental and orthostatic challenges

Cardiovascular responses to single stressors diminish over time. Interaction of different stressors influencing hemodynamic variables, indicative of stress-induced reactivity and physiological responses are, however, poorly understood. We investigated time course of mental (using mental arithmetic, MA) and orthostatic (using head up tilt, HUT) challenges induced responses in 16 males. Three protocols were used: HUT, MA and MA+HUT, with sessions randomized and two weeks apart. Hemodynamic responses were compared for 30s epochs of stress application (stress(T1), stress(T2)...). Compared to baseline, HUT, HUT+MA and MA applications affected heart rate (HR) (+15.1+/-8.0 bpm, +20.0+/-9.2 bpm, +11.9+/-7.2 bpm, all ps<.001, respectively) and stroke volume (SV) (-22.3+/-8.1 ml, -22.0+/-10.4 ml, -7.6+/-8.7 ml, all ps<.001, respectively). HUT and MA+HUT induced HR increases were higher in stress(T2) compared to stress(T1) (p<.05) and reached maximum at stress(T2). HUT and MA+HUT further reduced SV in stress(T2) as compared to stress(T1) (p<.001); lowest SV was in stress(T2). Mean arterial pressure reached its minimum in stress(T1) during HUT and MA+HUT (-6.0+/-8.5mm Hg, p<.001, -4.4+/-9.7 mm Hg, p<.01, respectively) but increased in MA (+4.3+/-3.7 mm Hg, p<.01). Combination of MA+HUT resulted in different time courses of blood pressure responses as compared to HUT alone. We conclude that application of single or combined stress challenges lead to stressor- and time dependent-initial changes in cardiovascular responses. Our findings provide novel insights regarding the duration a stressor must be applied to elicit maximal cardiovascular responses.

State-dependent changes of prefrontal–posterior coupling in the context of affective processing: Susceptibility to humor

The aim of the present study was to examine whether interindividual differences in the coupling or decoupling of prefrontal and posterior cortices during the exposure to social–emotional information may predict an individual’s positive emotional responsiveness. Susceptibility to humor was assessed in a behavioral paradigm several weeks after the EEG recordings. State-dependent changes of prefrontal–posterior EEG beta coherence were recorded during stimulation with other people’s auditory expressions of cheerfulness and sadness. Greater decreases of coherence during the stimulation with positive affect expressions prospectively predicted greater positive emotional responsiveness, indicated by higher amusement ratings in response to cartoons and higher scores in a questionnaire measure of exhilarability. Greater increases of coherence during the stimulation with negative affect expressions did not predict perceived funniness but were related to shorter response latencies to the amusement ratings. The results further support the notion that a more loose prefrontal–posterior coupling may be related to loosening of control of the prefrontal cortex over incoming emotional information and, thus, to a propensity to deeper emotional involvement and a greater impact of perceptual input, whereas increased prefrontal–posterior coupling may be related to strong control and the propensity to protect oneself from becoming emotionally affected.