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Biomedical subjects

D Vaitl

Publications and source records attributed to D Vaitl.

At least 37 records · Page 2Linked to original sources
PubMed1997

Latent inhibition and autonomic responses: a psychophysiological approach.

Latent inhibition, retarded learning after preexposure to the to-be-conditioned stimulus, has been implied as a tool for the investigation of attentional deficits in schizophrenia and related disorders. The present paper reviews research that used Pavlovian conditioning as indexed by autonomic responses (electrodermal, vasomotor, cardiac) to investigate latent inhibition in adult humans. Latent inhibition has been demonstrated repeatedly in healthy subjects in absence of a masking task that is required in other latent inhibition paradigms. Moreover, latent inhibition of Pavlovian conditioning is stimulus-specific and increases with an increased number of preexposure trials which mirrors results from research in animals. A reduction of latent inhibition has been shown in healthy subjects who score high on questionnaire measures of psychosis proneness and in unmedicated schizophrenic patients. The latter result was obtained in a within-subject paradigm that holds promise for research with patient samples.

Adult↗
PubMed1997

Shifts in blood volume alter the perception of posture.

Recent experiments have shown that somatic graviceptors exist in humans. Traditionally, extravestibular gravity information has been thought to originate from mechanoreceptors in the joints, muscles and skin. Experiments with normal, paraplegic and nephrectomized subjects revealed that the kidneys and the cardiovascular system are involved in providing truncal gravity information. The present study intends to determine the influence of shifts in body fluid, especially of the distribution of blood along the subjects' spinal (Z-) axis, on the perception of posture. To this end, the distribution of body fluids was altered by means of the technique of lower body negative and positive pressure (LBNP and LBPP). LBNP leads to venous pooling of blood in the legs, whereas LBPP prevents venous blood from pooling, increasing central volume. Changes in blood distribution were measured by segmental impedance cardiography for four body segments: the upper torso (thoracic cavity), lower torso (abdominal and pelvic region), thigh and calf. Seventeen healthy subjects (mean age: 27.3 years) participated in the experiment. They were positioned on the side (right-ear-down head position) on a tilt table which the subjects and the experimenter could tilt via remote control around an axis parallel to the subjects' visual (X-) axis. The experimenter set the initial tilt in total darkness to arbitrary angles while strictly alternating between head-up and head-down tilts. Subjects were then asked to rotate the board until they felt they were in a horizontal posture. Means and variances of eight pairs of settings were taken as a measure of the subjective horizontal posture (SHP). During LBNP (-30 mmHg), subjects perceived being tilted head-up, whereas LBPP (+30 mmHg) led them to feel tilted head-down. The results corroborate the hypothesis of an effect of the blood's mass on graviception and also indicate supplementary contributions of other visceral afferences.

Adult↗
PubMed1997

Fear and the startle reflex: blink modulation and autonomic response patterns in animal and mutilation fearful subjects.

The present study was designed to examine the pattern of startle reflex modulation and autonomic responses for individuals high in animal or blood-injury fear when viewing pictures of their feared objects. Sixteen individuals in each fear group and 16 low-fear control individuals viewed 32 color slides depicting fear-relevant, unpleasant but fear-unrelated, neutral, and pleasant scenes. Free viewing times were assessed in a second phase of the procedure as an index of avoidance behavior. Exposure to pictures of feared objects resulted in a consistent startle reflex potentiation and behavioral avoidance in both fear groups. This activation of the basic aversive system was independent of the autonomic pattern of the fear responses, which differed for the high-fear groups. These results suggest that the probe startle response indexes the organism's basic motivational disposition and add new information to the assessment of fear.

Adult↗
PubMed1997

Effects of low-frequency magnetic fields on electrocortical activity in humans: a sferics simulation study.

A previously recorded electromagnetic impulse of natural origin, a 10 kHz-sferic, was simulated and presented to 20 subjects. The magnetic component of the signal with a maximum field amplitude of 50 nT and a duration of 500 microseconds was applied over a duration of 10 minutes with a pulse repetition rate that varied statistically between 7 and 20 Hz. After sferics exposure, an additional 20 minutes without treatment were recorded in order to examine possible prolonged effects of sferics stimulation. The control group (n = 20) received no treatment. As a dependent measure, electrocortical changes throughout the course of the experiment were determined by means of EEG spectral analysis and compared between the two groups. Sferics exposure provoked increases in alpha and beta power. The effect was present during stimulation and continued for 10 minutes after the end of treatment. A longer lasting influence of sferics exposure was displayed by subjects with a high degree in weather sensitivity, somatic complaints, and neuroticism, who continued to stay on an enhanced alpha power level until the end of registration (20 minutes after the end of exposure). With these results a general electrocortical sensitivity towards sferics as well as individual differences in sferics reactivity could be demonstrated.

Adult↗
PubMed1996

Interoception.

During the last two decades, research on interoception has experienced a surprising renaissance. New experimental approaches and methods have revealed much about the processing of afferent signals from the inner organs of the body, and have allowed more accurate descriptions of these processes, as well as a more accurate determination of their functional significance in the experience and behavior of humans. Besides neuromuscular, respiratory, and gastrointestinal interoceptive processes, the cardiovascular afferent influences are now known to be very important. Invariably, the central questions concern sensitivity to signals from the body, factors which may influence judgement of perception, and the degree to which conventional hypotheses regarding the interoceptive capabilities of humans may require revision. Findings from general psychological and clinical studies have shown that humans may attain remarkable levels of interoceptive performance. On the other hand, they also show how deep the chasm is between visceral processes and perception, and between that which is perceived and the reports thereof. Only interdisciplinary approaches to these complex processes promise success.

Autonomic Nervous System↗
PubMed1996

Simulated micro-gravity and cortical inhibition: a study of the hemodynamic-brain interaction.

The present study was carried out to determine the inhibitory cortical processes induced by changes in hemodynamics. Previous experiments in humans conducted in our laboratory have shown that there is a close relationship between posture and delta and theta EEG activity. The most pronounced effects were obtained during the 6 degrees head-down tilt (HDT) position. In space medicine the HDT procedure is very frequently employed to simulate micro-gravity and to determine the neurohormonal counter-regulations evoked by the expansion of central volume. Twenty male subjects spent 23 h in bed in 6 degrees HDT and 23 h in 6 degrees HUT (head-up tilt) positions during which EEG (frontal, central, parietal, occipital), startle responses, and reaction-times were measured every 2 h (from 10:00 h till 20:00 h). The effects of cardiovascular deconditioning (CD) regularly occurring after HDT were assessed by examining orthostatic tolerance and the physical work capacity (bicycle ergometry). As expected, 23 h HDT led to more pronounced CD than HUT. Spectral power analyses of EEG revealed increases in delta and theta frequency hands similar to those found during HDT in previous EEG studies. In addition, subjects responded more slowly (S1-S2 reaction-time task) during HDT as compared with HUT bedrest. The influence of HDT on startle response, however, was not in keeping with the initial hypothesis (i.e. dampening of reflex activity). The EEG data and the sensorimotor performance indicated that the body fluid shift towards the thoracic cavity induced by HDT resulted in signs of cortical inhibition. In addition to neural mechanisms, other processes must be postulated which are closely related to the counter-regulation evoked by the varying body positions.

Adult↗
PubMed1996

Affective learning: awareness and aversion.

In two studies, we investigated the influence of aversive and nonaversive reinforcers on startle reactivity, visceral responses, and self-report during Pavlovian conditioning. Furthermore, we assessed how awareness of the stimulus contingencies affect conditioned discrimination in the different response systems. Conditioned potentiation of the startle response was only observed in the context of aversive learning. Moreover, blink potentiation occurred without awareness of the relationship between the conditioned and unconditioned stimulus. In contrast, skin conductance conditioning was independent of the aversiveness of the reinforcer and was only obtained for those individuals who could correctly verbalize the stimulus contingency in a postconditioning recognition test. Cardiac responses varied with the task demands of the situation and covaried with individual response stereotypes.

Adult↗
PubMed1996

Covariation bias and paranormal belief.

22 believers and 20 skeptics of extrasensory perception (ESP) participated in a telepathy experiment. Subjects were asked to judge the covariation between transmitted symbols and the corresponding feedback given by a receiver. Believers overestimated the number of successful transmissions ('hits'). Skeptics were characterized by accurate hit judgments. For believers, positive correlations between hit-responses, their heart rates, and their experienced arousal were found. In addition, subjective arousal was positively associated with the hit estimates given at the end of the experiment. This response pattern was absent in the group of skeptics. It is concluded that covariation bias as a psychophysiological concept plays an important role in the maintenance of paranormal belief.

Adult↗
PubMed1991

Sympathovagal interaction during mental stress. A study using spectral analysis of heart rate variability in healthy control subjects and patients with a prior myocardial infarction.

We tested the hypothesis that psychological stress testing in the clinical laboratory provokes changes in the sympathetic and vagal activities regulating heart rate that can be assessed noninvasively using spectral analysis of RR variability. To account for the effects on respiration produced by talking, this study was performed with two different procedures: the I.K.T. (i.e., a computer-controlled mental task that is performed in silence and does not entail human confrontation) and a stressful interview. Finally, we assessed whether ischemic heart disease modifies the spectral changes induced by psychological stress by comparing a group of healthy subjects (age, 38 +/- 2 years) with a group of patients (age, 52 +/- 3 years) recovering from 1-month-old myocardial infarctions. The findings indicate that psychological stress induced marked changes in the sympathovagal balance, which moved toward sympathetic predominance. The low-frequency component of RR variability, a marker of sympathetic activity, increased from 58 +/- 5 normalized units (NU) to 68 +/- 3 NU with the I.K.T. and to 76 +/- 3 NU with the interview. This increase was absent in the group of post-myocardial infarction patients. However, arterial pressure increased significantly in both groups of subjects. The possibility of age playing an important role in determining the differences observed was disproved by the findings of a marked increase in low frequency with mental stimuli in an additional group of borderline hypertensive subjects with ages (55 +/- 2 years) comparable to those of post-myocardial infarction patients.

Adult↗
PubMed1989

Fear conditioning, meaning, and belongingness: a selective association analysis.

Twenty-three subjects rated the belongingness of pairs of conditionable (photographic slides) and unconditioned (e.g., shock, tone, human scream) stimuli. Forty new subjects were then classically conditioned, using rating-defined high (angry face/scream) and low (landscape/scream) belongingness pairs. Finger-pulse responses to the high-belongingness pairs showed superior acquisition and resistance to extinction. Another 40 subjects were conditioned to compound stimuli: a slide (either landscape or angry face) that was the same over trials, and a yellow or blue background that was the discriminant cue for the unconditioned stimulus (scream). When the angry face (the high-belongingness slide) was the invariant part of the compound, relatively poorer differential pulse-volume and skin-conductance conditioning was observed. Thus, depending on the task, a priori belongingness rendered stimuli selectively conditionable, either enhancing or inhibiting visceral response associations.

Association↗
PubMed1989

[Objective and simulated stimulation: an empirical study of the effect of indirect suggestion on motor behavior].

In an experimental investigation it is demonstrated that motor behavior-in contrast to the opinion forwarded in the literature-is not only elicitable by means of direct persuasion, but also to a great extend by mere indirect suggestion, (feigning of stimuli). A differential investigation of these effects provided evidence that reactions to feigned stimuli are highly person specific and relatively homogenous concerning the respective instruments whereas objective stimuli lead to reactions relatively specific for the respective instrument applied. The findings are interpreted as an analog on to placebo-effects in the area of motor behavior. Their extend may be seen as an argument for a stronger concern with subjective reaction tendencies in this field.

Adolescent↗
PubMed1989

[Current empirical data on conditions in relation to death in the hospital].

This survey-study represents the psycho-social conditions of death in West-German hospitals as seen from different occupational groups. The test, developed for this task, has been applied in 70 hospitals of different federal states, medical-departments and supporters. It is shown that following factors have an essential influence on the attitudes of people to the needs of the dying patient: amount of medical engineering at ward, time of professional activity and status of the personnel. In sum, the study gives a dark picture of death situation. Most helpers hold that situation inhumane. This is a burden for the helpers themselves. The results of the study tell against the efficiency of actual engagement in dying patients. The author develops some proposals, how the requests of thanatology that were adequat to improve the actual situation, could better be transferred to the practice.

Attitude of Health Personnel↗
PubMed1989

[A mechanical method for changing heart rate and blood pressure].

The investigation of afferent cardiovascular influences upon central nervous processes needs a methodology which allows for independent and systematic manipulation of circulatory processes. By mechanical manipulation of posture (tilt table, orthostasis) and compression of lower body parts (by anti-G-suit) reliable changes in heart rate and blood pressure can be induced. In fourty subjects (study 1) it could be shown that sustained (30 min.) changes in heart rate (e.g. orthostatic tachycardia, decrease of heart rate during compression) and mean arterial blood pressure (increase during orthostasis with and without compression) occur. Although changes in heart rate could be achieved irregardless of whether the venous "pooling" was suppressed by an air- or water-filled pressure suit, the pressor effect did differ quite considerably. In fourty-four subjects (study 2) it could be demonstrated that only by means of an water-filled suit further increases in mean arterial blood pressure could be evoked during orthostasis. Changes in hemodynamic also lead to changes in sympatho-vagal control of cardiac activity. In study 3 (ten subjects) it could be shown, that orthostasis mainly evokes alterations in sympathetic activity whereas lower body compression leads to additional increases of vagal activity and respiratory sinus arrhythmia during orthostasis.

Adolescent↗