PubMed Health⌕ Search

Biomedical subjects

U Erdmann

Publications and source records attributed to U Erdmann.

At least 19 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↗
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↗
PubMed1989

Psychophysical assessment of sinusoidal whole-body vibration in z-axis between 0.6 and 5 Hz combined with different noise levels.

Nine healthy sitting males evaluated the intensity of vertical whole-body vibration (WBV) in z-axis at four frequencies (F1 = 0.63 Hz, F2 = 1.25 Hz, F3 = 2.5 Hz, F4 = 5 Hz) and two intensities (I1 = 1 ms-2 rms, I2 = 2 ms-2 rms) by cross-modality matching (CMM). The subjects were simultaneously exposed to low-frequency noise at two levels (L1 = 65 dBA, L2 = 86 dBA). L1 and L2 were context conditions which did not have to be evaluated by CMM. The results indicate a flat response between F2 and F3; the sensitivity increases towards F1. Different exponents of Stevens' power law for the frequencies of WBV contradict the frequency range tested to be a sensory continuum. L2 caused practically significantly stronger sensations of the WBV-intensity from F1 to F3 (I1) and at F2 (I2). No synergistic effect of noise and WBV was shown at F3I2. Weighting factors were calculated for all exposure conditions using Stevens' power law. The weighting of F2 and F3 contradicts that of the International Standard ISO 2631-1985 (E). The results enable recommendations for the frequency weighting of WBV between 0.63 and 1 Hz, as well as for the equivalence of noise and WBV with combined exposure.

Adult↗
PubMed1989

[The effect of low-frequency whole-body vibration on the vestibular apparatus].

For the first time, effects of very low-frequency whole-body vibration (WBV) on the functional state of the vestibular system were examined by means of electronystagmography (ENG) which is considered as a sensitive and adequate method. During vertical WBV-exposure with 0.6 Hz and 1.87 ms-2 rms for 50 minutes, a vertical nystagmus was observed. The results suggest the applicability of the ENG under laboratory conditions with WBV-exposure as a method for the assessment of the vestibular function. Changes of ENG amplitudes occurred with longer duration of WBV-exposure; they were different between subjects.

Adult↗
PubMed1988

Isolated and combined effects of prolonged exposures to noise and whole-body vibration on hearing, vision and strain.

This study was carried out in order: (1) to examine the effects of isolated and combined prolonged exposures to noise and whole-body vibration on hearing, vision and subjectively experienced strain, and (2) to check the combined effects with repeated exposures. Six male subjects were exposed twice to noise (N) at 92 dBA, whole-body vibration (V) in the Z-axis at 4 Hz and 1.0 ms-2 rms, and noise and vibration (NV) for 90 min with each condition. Temporary threshold shifts of hearing (TTS) and their integrals (ITTS) were measured at 4, 6, 10, and 12 kHz. Visual acuity was examined by means of a very sensitive test. Cross-modality matching (CMM) of the handgrip force was used to judge the subjectively experienced strain. NV induced a clear tendency of higher TTS and ITTS than N, with several significant differences most pronounced at 10 kHz. With repeated exposures, the effect of NV decreased, while the reactions to N and V remained unchanged. The individual reactions to NV differed. The influence of the duration of exposures on vision depended on the condition; N caused time-dependent changes, whereas V did not. CMM-data increased with the duration of the exposure during V and NV. N was generally judged to be more straining than V; NV caused higher strain than V during the first 30 min of exposure only. Correlations between different effects suggest certain links between them. Additionally, less motivation--daily obtained by a questionnaire--often correlated with higher ITTS during N and NV. The results also illustrate the combined effects on the individual susceptibility, repetition of exposure, the kind of response, and, possibly, the actual psychic state.

Adolescent↗
PubMed1988

Examination of spinal column vibrations: a non-invasive approach.

Accelerations of vertebrae during whole-body vibration (WBV) are used in occupational biomechanics for the prediction of internal stress. To avoid invasive techniques, a method for the calculation of bone accelerations was developed using measurements on the skin. The soft tissue between spinous processes L3 and T5 and miniature accelerometers stuck to the skin over them was modelled by a simple Kelvin element, whose parameters i.e. angular natural frequency omega n and critical damping zeta, describe an approximate transfer function between the bone (input) and the skin surface (output). The parameters were determined from free damped oscillations of the accelerometer-skin complex in the Z-axis, and depended significantly on the factors "subject" and "point of measurement". In one subject, the time courses of bone accelerations during sinusoidal WBV (4.5 and 8 Hz; 1.5 m.s-2 RMS) were calculated using separate transfer functions for each of 11 different spinal levels. Since the output signals on the skin were non-sinusoidal, the skin accelerations had to be treated with an inverse transfer function in the frequency domain. A comparison of accelerations measured on the skin and predicted for the bone mainly indicates that absolute peak values of bone accelerations are smaller and occur earlier. Both kinds of acceleration hint at differences in WBV-induced internal stress within the spine.

Bone and Bones↗
PubMed1986

Sex- and age-related behaviour of the integrated EMG during one-arm cranking.

There are load-dependent increases in the bioelectrical activity (iEMG) of muscles of the shoulder and the right upper extremity and selected parameters of the cardiopulmonary system. At comparable loads the amplitudes of the EMG were higher in the group of men than in the group of women. The iEMG values were found to be higher in the younger group of women than in the older one. The higher values of iEMG of the younger women corresponded to a higher oxygen uptake and higher heart rate as well as to a lower physical endurance. The physical endurance limit (derived from behaviour of the EMG) was estimated at 5 watts (women) and 10 watts (men).

Adult↗
PubMed1978

[Homogenization of the dose to the target volume in case of irregular body-surface by means of compensation (author's transl)].

Irregular body-surface contours in the treatment part of high-energetic photon fields are producing an inhomogeneous dose distribution within the target volume. Homogenization of the dose is necessary in order to avoid over- or underdosage. A technique of making compensators is described. These are individual compensation filters substituting tissue layers which are lacking, they are correctly scaled down and optimally corrected in view of absorption and scattering according to the actual irradiation conditions. A simple mechanical device makes possible the production of a mould for heavy-metal compensators immediately in the course of scanning of the body-surface. A universal semi-automatic version of this method is appropriate to clinical practice; it records optically, and therefore without contact and quickly, all body-contours desired. By means of the image of moiré contour-lines thus obtained can be made the mould for the compensator in a second operation using an electronically controlled copy-milling machine.

Filtration↗