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Biomedical subjects

R Haschke

Publications and source records attributed to R Haschke.

18 recordsLinked to original sources
PubMed1995

The healthy volunteer in clinical pharmacology: personality and motivation.

The aim of the present study was to quantify the personality structure and motivation of medical students, who are often the most readily available source of healthy volunteers, since it has long been known that the pharmacodynamics and pharmacokinetics of drugs can be substantially modified by predominant personality traits (e.g. neuroticism, extraversion). Over the course of 4 years, a total of 337 subjects (165 males, 172 females) out of the 496 medical students asked, participated in the study after appropriate instruction. Students were tested using the Motivation Q-Sort method which, by means of questions ("questionnaire sort"), investigates whether a subject tends to react in a success-motivated (SM) or a failure-motivated (FM) mode. The variable measured is the so-called net hope (NH), where NH > 1.6 corresponds to SM and NH < -0.3 corresponds to FM. We also used the Freiburg Personality Inventory (FPI) as a suitable method of determining personality structure. The predominant traits of interest found were nervousness (FPI 1), extraversion (FPI E), and neuroticism (FPI N). In the first series of tests (primary selection), motivation only was determined in 337 volunteers. The range was fairly broad, with NH values from 4.32 (highly SM) to -3.09 (highly FM). In the second series of tests, about 60 SM and 60 FM subjects were selected. The Motivation Q-Sort method was repeated with students placed under more difficult conditions, and the FPI was also performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Differences in mental task performance and slow potential shifts in subjects differing in cortisol level.

Hormones of the pituitary-adrenocortical axis (e.g., cortisol) are involved in the regulation of brain function. This study was aimed to clarify whether individual differences in baselines of cortisol are related to differences in heart rate (HR), slow brain potential shifts (SPS), performance data and personality. 17 males were instructed to solve 120 arithmetical tasks under time stress conditions. They could obtain monetary bonuses according to the accuracy of their task performance. This test condition was compared to a control condition. To determine the plasma level of cortisol by radioimmunoassays four blood samples were collected during the session. Baselines were estimated twice. A clustering procedure with respect to all cortisol levels resulted in a group of high responders (HC, n = 9) and a group of low responders (LC, n = 8). The HR was significantly higher in the HC group. The SPS of the LC group were characterized by a larger P300 elicited by the task followed by a steep negative slow wave (NSW) as compared to the HC group. LC subjects also showed a higher NSW before feedback presentation. The LC group solved the tasks faster and obtained more than twice the reward than the other group. They scored higher in achievement motivation and also reported increased 'Social Acceptance' and decreased 'Tiredness'. In sum, the results suggest a more efficient regulation of the arousal level of the LC group in contrast to the HC group as far as reflected in the parameters analysed.

Adolescent↗
PubMed1990

[Changes in the general activation level in psychophysiologic studies--II. Values of auditory evoked potentials in relation to impression and perception and heart rate].

In psychophysiology all procedures used are accompanied with changes of general activation level (GAL) of the subjects. In our study these changes are characterized by self-assessment of the internal state and by the mean heart rate (HR) of each period. On the basis of these data group mean auditory evoked potentials (AEPs) were computed. The influence of the GAL on the N 110- and P 190-amplitudes of the AEPs was analysed. There was no effect on the P 190-amplitude whereas the N 110-amplitude shows distinct responses on changes in GAL. These amplitudes diminished when the subjects reported a change of internal state. The diminishing of N 110-amplitudes took place as well at an increase as at a decrease of the internal state factors. Comparing the HR and the N 110 of the AEPs we found an inverse U-shaped dependence. These results are discussed in comparison to the literature. Furthermore a model which could elucidate the observed findings is presented for a critical discussion.

Adult↗
PubMed1989

[Activity status in psychophysiologic studies. "Changes in the general activity level in psychophysiologic studies--an analysis of objective and subjective parameters"].

The general activation level (GAL) is one of the sources of influence in psychophysiological experiments. That means most of the results are dependent on the GAL. Taken this into account one can furthermore elucidate a part of the high variability of the interesting physiological data. We analysed heart rate (HR), auditory evoked potentials (AEP) elicited by background stimuli and the subjective assessment of the internal state of the subjects to describe changes of the GAL. Summarizing the results we can show different influences of the GAL on the physiological data. Changes of HR and AEP-parameters are caused by specific experimental conditions. The distinct influence of the subjective state of the subjects on the AEP-shapes allows the conclusion that subjective data should be more taken into consideration. The comprehensive characterization of the GAL requires data of different integrative levels.

Adult↗
PubMed1987

Comparison of principal components computed with principal factor analysis on the basis of averaged and single-trial ERPs using the Fischer-Roppert procedure.

Averaged and single-trial event-related potentials (ERPs) were analysed using the Principal Factor Analysis (PFA) with following varimax rotation, and the results were compared. The correspondence between the matrices of factor loadings was tested by means of the Fischer-Roppert-procedure. For the application of PFA, a preceding averaging to improve the signal to noise ratio is not necessary. If the group of subjects is homogeneous enough, the analysis of the single-trial ERPs provides results sufficient to investigate the component structure of the ERP. The ERPs from all subjects can be described with one common component structure.

Arousal↗
PubMed1987

ERP analysis of reafferent information processing during the performance of an arithmetical task.

Reafferent information processing accomplished by distributed cerebral systems was studied by analysing concomitant event-related potentials (ERPs) elicited by weak electrical stimulation of the skin of the hand. The subjects were instructed to interpret this stimulus as feedback information indicating whether their solution of an arithmetical task was correct or not. ERPs elicited by positive or negative feedback signals showed striking differences. ERPs were also influenced by the subject's confidence in the correctness of the solution, while probability of stimulus occurrence was less important in the design. Neurophysiological implications of ERP-disclosed influences on feedback processing are discussed.

Adult↗
PubMed1986

Extracellular fluid volume during pneumothorax and hypoxemia in rabbits.

This study was designed to test the hypothesis that persistent pneumothorax of greater than or equal to 6 days duration causes a decrease of extracellular fluid volume (ECF). Such changes are of interest as they may be causally related to persistent hypotension that has occurred in humans following pneumothorax evacuation. Experiments were done in rabbits to determine the effect on ECF of persistent pneumothorax with or without systemic hypoxemia. Animals were divided into four treatment groups: 1) pneumothorax with hypoxemia [fractional concentration of O2 in inspired gas (FIO2) = 0.21, n = 30], 2) pneumothorax without hypoxemia (FIO2 = 0.40, n = 25), 3) hypoxemia alone (FIO2 = 0.14, n = 11), and 4) normal controls (FIO2 = 0.21, n = 15). Measurements of ECF were made in the base-line control state and after 6 days of treatment using the dilution volume of thiocyanate sodium as an estimate of ECF volume. We found a reduction of ECF in 53% of animals with pneumothorax plus hypoxemia (range -47% to +13%) and in 54% of animals with hypoxemia alone (range -26% to +25%). ECF declined in only 7% of normal controls and 20% of animals with pneumothorax without hypoxemia. Arterial O2 tensions after 6 days of treatment were 58 +/- 12.6, 141 +/- 28, 60 +/- 5.1, and 97 +/- 9.3 Torr (mean +/- SD) in groups 1-4, respectively. The results suggest that pneumothorax with hypoxemia or hypoxemia alone may contribute to depletion of ECF, but this response is variable and unpredictable in individual animals.

Animals↗
PubMed1985

Endogenous plasma proteins in edematous lungs and alveolar fluid in rabbits.

In this study, we compared two methods of differentiating hydrostatic and permeability types of pulmonary edema. The first method entailed measurement of protein concentrations directly in samples of alveolar fluid (AF); the second method was an indirect technique in which protein concentration in extravascular extracellular water (EVECW) was calculated on the basis of separate measurements of the quantity of protein in the lung and the volume of EVECW. The concentration of albumin (Alb) and gamma-G-globulin was measured in EVECW and alveolar fluid in excised edematous rabbit lungs. Edema was caused by elevation of left ventricular end-diastolic pressure to 25 Torr (hydrostatic edema, HE) or by intravenous oleic acid, 0.09 ml/kg (permeability edema, PE). The volume of distribution of Na+ was utilized as a measure of EVECW in the lung. Protein concentration in EVECW and AF relative to plasma (EV/PL and AF/PL, respectively) was compared in the two types of edema. The EV/PL was 0.61 +/- 0.12 (SD) for Alb in He compared with 1.18 +/- 0.47 in PE (P less than 0.02). The AF/PL was 0.54 +/- 0.12 and 1.25 +/- 0.33 in HE and PE, respectively (P less than 0.001). There was good correlation between EV/PL and AF/PL for Alb (r = 0.74, P less than 0.001) but not for gamma-G-globulin. Thus EV/PL for Alb, AF/PL for Alb, and gamma-G-globulin all differentiated hydrostatic from permeability edema.

Animals↗
PubMed1979

[Analysis of hippocampal sensory EP-changes in dependence on activation level].

Photically evoked potentials were recorded from the visual cortex (VC) as well as CA 1/2- and CA 4/Fascia dentata-region of the dorsal hippocampus in alert resting rabbits. Analysing the whole time-course of the individual hippocampal EP attention was focused on components corresponding in time to the late negative complex of the cortical EP. Enhancement of such components was seen following habituation to repeated flashes. These changes occurred concerning components in the CA 4/FD-record with shorter latency. The duration and peak latency, however, was longer in CA 4/FD than in the other records. During stimulation of the medial septal nucleus a diminution of late EP-components was seen in the visual cortex and less pronounced in the hippocampus. The time-course of the changes was almost the same in VC and CA 4/FD, whereas in CA 1/2 later components were affected. RF-stimulation caused very similar changes, while those in hippocampal EP's were extended up to later components. Whereas the time range of changes in the hippocampal EP's to all influences under investigation was almost the same, in the VC by RF-stimulation in contrast to habituation components with shorter latencies were affected. In this way it is supposed that for the VC different processes are affected by the three influences, while this could not be established for the hippocampus.

Animals↗
PubMed1978

[Comparison of evoked potential changes from lateral geniculate body and visual cortex by stimulation of the medial septal nucleus and mesencephalic reticular formation in rabbits].

Evoked potentials to flash from visual cortex (VC) and corpus geniculatum laterale (Cgl) were observed in alert resting rabbits. The direction and volume of changes in the late negative complex (sn-) of the EP were investigated during repetition of light flashes only (habituation), during stimulation of septum and reticular stimulation (RFmes). Habituation showed an increase of amplitudes during the sn-complex, which was started first in Cgl, had its maximum earlier and lasted longer in the Cgl than in the visual cortex. Septal stimulation in the majority of experiments caused diminution of these EP-components almost synchronously in the VC and Cgl. Reticular stimulation gave rise to diminution of amplitudes during the sn-complex, which started first in the VC, where it had its maximum earlier and lasted longer than in the Cgl too. Our results show that all three influences under investigation caused typical but different changes of processes underlying EP of the visual cortex and lateral geniculate body.

Animals↗
PubMed1975

[A simple method for the evaluation of differences in averaged evoked potentials as demonstrated of visual evoked potentials changed through hippocampal stimulation].

A simple method is presented which by subtraction of amplitudes of averaged evoked potentials (AEP) within regular time-intervals enables us to estimate differences in the course of the potential. First results demonstrate that all parts of the potential may be influenced and that most striking differences must not necessarily occur in the peak region of the AEP. The late negative complex of the AEP is likely to be a result of summation of some subcomponents, which may be altered differently. The method presented allows exact measurements of each of them.

Animals↗