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Biomedical subjects

G Freude

Publications and source records attributed to G Freude.

18 recordsLinked to original sources
PubMed2001

Auditory probe sensitivity to mental workload changes - an event-related potential study.

The goal of this study was to explore the utility of parameters of ERPs for assessment of mental workload during performance of complex tasks. In addition to a baseline auditory oddball task, 15 healthy adult volunteers performed gauge monitoring (Gauge) and mental arithmetic (Math) separately and together. Throughout the task performance three types of auditory stimuli were presented as probes, i.e. 80% 1000 Hz tones, 10% 2000 Hz tones and 10% novel sounds. The ERP components N1 and P3 were analysed, which are assumed to reflect perceptive and central processing resources. The results interpreted in the framework of capacity theory indicate high demand on processing resources already during separate performance of both tasks Gauge or Math. During simultaneous performance the workload on average exceeded the limits of processing capacity: the performance data impaired significantly. The ERP measures N1 and P3 were confirmed in their sensitivity and diagnosticity. By using novel sounds as probes with involuntary attention-capturing properties, one might overcome a problem of the irrelevant probe technique, i.e. whether the operator spends his spare capacity for processing of the irrelevant probes.

Acoustic Stimulation↗
PubMed2000

Microwaves emitted by cellular telephones affect human slow brain potentials.

The influence of electromagnetic fields (EMF) emitted by cellular telephones on preparatory slow brain potentials (SP) was studied in two experiments, about 6 months apart. In the first experiment, a significant decrease of SP was found during exposure to EMF in a complex visual monitoring task (VMT). This effect was replicated in the second experiment. In addition to the VMT, EMF effects on SP were analysed in two further, less demanding tasks: in a simple finger movement task to elicit a Bereitschaftspotential (BP) and in a two-stimulus task to elicit a contingent negative variation (CNV). In comparison to the VMT, no significant main EMF effects were found in BP and CNV tasks. The results accounted for a selective EMF effect on particular aspects of human information processing, but did not indicate any influence on human performance, well-being and health.

Adult↗
PubMed1999

Slow brain potentials in a visual monitoring task.

The purpose of this study was to analyse slow brain potentials (SPs) during visual monitoring, needed to perform the clock-monitoring task (CMT). This task was successfully applied in behavioural studies, in which attention capabilities were investigated in dependence on individual factors. Clearly pronounced preparatory SPs were observed during the CMT reflecting a high level of preparation and attention, necessary for achieving high performance accuracy. The well-known influence of task repetition on SPs and the relation between SP and behaviour were confirmed. The practicability of the CMT, the clear and easily detectable SP components and the sensitivity of the present approach makes it recommendable for further applications, e.g. for the evaluation of the effects of occupational/environmental exposures on processes of information processing.

Adult↗
PubMed1998

Mobile phones modulate response patterns of human brain activity.

Mobile phones emit a pulsed high-frequency electromagnetic field (PEMF) which may penetrate the scalp and the skull. Increasingly, there is an interest in the interaction of this pulsed microwave radiation with the human brain. Our investigations show that these electromagnetic fields alter distinct aspects of the brain's electrical response to acoustic stimuli. More precisely, our results demonstrate that aspects of the induced but not the evoked brain activity during PEMF exposure can be different from those not influenced by PEMF radiation. This effect appears in higher frequency bands when subjects process task-relevant target stimuli but was not present for irrelevant standard stimuli. As the induced brain activity in higher frequency bands has been proposed to be a correlate of coherent high-frequency neuronal activity, PEMF exposure may provide means to systematically alter the pattern fluctuations in neural mass activity.

Acoustic Stimulation↗
PubMed1998

Effects of microwaves emitted by cellular phones on human slow brain potentials.

The influence of electromagnetic fields (EMF) emitted by cellular phones on preparatory slow brain potentials (SP) was studied in two different experimental tasks: In the first, healthy male human subjects had to perform simple self-paced finger movements to elicit a Bereitschaftspotential; in the second, they performed a complex and cognitive demanding visual monitoring task (VMT). Both tasks were performed with and without EMF exposure in counterbalanced order. Whereas subjects' performance did not differ between the EMF exposure conditions, SP parameters were influenced by EMF in the VMT: EMF exposure effected a significant decrease of SPs at central and temporo-parieto-occipital brain regions, but not at the frontal one. In the simple finger movement task, EMF did not affect the Bereitschaftspotential.

Brain↗
PubMed1996

The differential effects of extremity and movement side on the scalp distribution of the readiness potential (RP) and the stimulus-preceding negativity (SPN).

In a time estimation task subjects had to press a button 3 s after the presentation of a warning stimulus. Two seconds after the movement they were informed about their performance by a knowledge of results (KR) stimulus. Preceding the movement a readiness potential (RP) and prior to the presentation of the KR stimulus a stimulus-preceding negativity (SPN) was recorded. Movement side (left/right) and extremity (hand/foot) were varied within subjects to demonstrate that the RP but not the SPN is affected by such manipulations. The scalp distribution of the late part of the RP was affected by movement side and extremity. Yet it exhibited the expected lateral asymmetry only preceding a movement of the left hand or of the right foot. The scalp distribution of the SPN was not affected by extremity. The size of the right hemisphere preponderance of the SPN depended on movement side following a finger flexion, but not following a plantar flexion of the foot. The experimental design was intended to avoid the temporal overlap between movement-related and stimulus-related activity. Yet it is argued that both results of this experiment can best be explained by such an overlap.

Adolescent↗
PubMed1990

[Intravaginal culture--simplification of IVF].

Initial results with intravaginal cultures (IVC) of human oocytes are reported. Up to 5 oocytes are harvested by follicular puncture guided by transvaginal sonography. Together with washed spermatocytes (final concentration 0.1 to 0.15 x 10(6)/tube) these are transferred to a plastic capsule filled with Menezzo B2 medium. After air-tight closure the capsule is placed into the patient's vagina and left in situ for 48 to 52 hours. Capsule loss is prevented by plugging the vagina with a tampon of appropriate size. In the first 15 females undergoing IVC fertilization was obtained in 56% of cases. Three intact pregnancies were recorded after embryo transfer. Of these, 2 occurred in the group of patients with tubal infertility and one in the group with tubal infertility and an additional andrologic abnormality. Our results and the reports by others suggest that IVC may well facilitate the technique of IVF. Potentially detrimental effects of light exposure and temperature variations on the gametes during conventional IVF are minimized. The more active involvement of the patients is an added psychological benefit.

Cells, Cultured↗
PubMed1990

[Special aspects of abdominal adhesions in gynecology].

Even minor adhesions in the oviduct or in the ovarial region may lead to infertility. In a controlled trial the adhesion status was documented in 103 patients who underwent microsurgical operations for infertility. Solutions of (a) streptokinase/streptodornase, (b) hydrocortisone acetate or (c) Ringer's solution only were administered intraperitoneally as adhesion prophylaxis. During a control laparoscopy 1 week after the primary operation, newly formed adhesions of mainly intermediate extent were observed in about 10% of the patients. There was no significant difference in efficacy between the prophylactic treatment.

Combined Modality Therapy↗
PubMed1990

[The significance of slow brain potentials for the estimation of activation processes in activities at the video-screen model workplace].

Numerous studies have shown that the slow potentials registered in the EEG allow conclusions on changes in activation processes preceding different activities. The Bp which has so far been analysed preferably as motoric phenomenon, is in the following used to furnish evidence of activation processes preceding mental performance at a visual display terminal. The analysis reveals the relationships between the Bp and mental load, mental performance, and a varying dynamic activation. From that, conclusions can be drawn already in the phase of preparing different information processing activities on variations in central-nervous activation and most likely even on the readiness to perform and the reliability of actions.

Action Potentials↗
PubMed1988

The Bereitschaftspotential in preparation to mental activities.

Earlier studies had investigated the Bereitschaftspotential (Bp) under different aspects of muscular activities. The present experiments were designed to test whether the Bp will be affected by the degree of mental load while motor activity is kept constant. Fourteen healthy male subjects had to solve arithmetical tasks under a graduated time pressure (3 categories of tasks). The subjects had to indicate by pressing one of three keys (trigger), which category of task they wanted to solve next. As soon as a key had been pressed, a task appeared on the computer display and disappeared after the time interval corresponding to the selected category. The results had to be entered into a computer via a keyboard. The EEG signals (5 s time constant, 15 Hz upper frequency cut-off) were averaged time-locked to the movement onset, starting 1.5 s before the pressing of the key. Trials with artefacts were rejected from averaging. The Bp was found to be significantly higher when the tasks were to be solved under higher time pressure. We assume that this might be rather an expression of an appropriate self-activation for the expected mental task than due to a different motor preparation.

Adult↗
PubMed1987

Changes in Bereitschaftspotential during fatiguing and non-fatiguing hand movements.

This study investigates the electroencephalographic Bereitschaftspotential (Bp) during muscular-fatiguing and non-fatiguing rhythmical hand contractions at 20%, 50%, and 80% maximum voluntary contraction (MVC). A feedback arrangement was provided so that subjects were able to adjust the force as required. The results confirm that Bp depends on force level. An increase in force results in a Bp increase. Further, they show that muscular-fatiguing contractions at 80% MVC are accompanied by an increased Bp. This could be the result of an increase in the central nervous activation required when preparing for motor activity with fatigued muscles. A decrease in Bp was observed during non-fatiguing repetitive hand contractions at 50% MVC. Possibly, the decrease reflects a decrease in subjects intentional involvement due to the monotony of the exercise. Repetitive movements at 20% MVC, which require a high degree of concentration and attention to adjust exactly to this very small force level, also result in an increased Bp, perhaps due to the higher intentional involvement. It may be concluded that the influence of muscular fatigue on Bp should be investigated with consideration of the psychological aspects of repetitive movements.

Adult↗
PubMed1987

[The readiness potential--movement-correlated changes in bioelectric brain activity].

The Bereitschaftspotential which belongs to the group of slow potentials can be recorded in the period of preparation to a voluntary motor act and is connected with changes of the level of central nervous activation. This paper is concerned with general questions of classification of Bp in the complex of movement-related brain potentials, with the topographic distribution over the scalp, and with the relation of Bp to some motor functions of the cortex. The relationship to psychological factors affecting the Bp is discussed.

Arousal↗
PubMed1983

[Theory and practice in the care of diabetic pregnancy--a timely concept].

Perinatal mortality in diabetic pregnancy has decreased markedly over the past 25 years; this reduction in fetal loss can be attributed to a variety of advances. These include technologic advances in obstetrics and pediatrics, as well as greater understanding of the metabolic aberrations occurring in pregnancy complicated by diabetes. Basically it seems convenient to consider the various disorders in cases of diabetes in pregnancy from several points of view: 1. the effect of pregnancy on the maternal diabetes and 2. the effect of maternal diabetes on the pregnancy and especially on the fetus, and from the above results we can consider 3. an actual procedure in the care of diabetic pregnancy. Regarding the necessary criteria in the care of pregnant diabetics neither pregnancy nor delivery will cause any serious problems.

Blood Glucose↗