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Biomedical subjects

P Ullsperger

Publications and source records attributed to P Ullsperger.

At least 19 recordsLinked to original sources
PubMed1992

Effects of isolated and combined exposures to whole-body vibration and noise on auditory-event related brain potentials and psychophysical assessment.

Auditory event-related brain potentials (ERP) in response to two different tone stimuli (1.1 kHz or 1 kHz, 80 dB, 50 ms; given by headphones at a regular interstimulus interval of 5 s with a probability distribution of 70:30) were recorded from 12 healthy male subjects (Ss) during four different conditions with two repetitions: A-60 dBA white noise (wN), no whole-body vibration (WBV); B-60 dBA wN plus sinusoidal WBV in the az-direction with a frequency of 2.01 Hz and acceleration of 2 m.s-2 root mean square; C-80 dBA wN, no WBV; D-80 dBA wN plus WBV. Each condition consisted of two runs of about 11 min interrupted by a break of 4 min. During the break with continuing exposure, but without auditory stimuli, Ss judged the difficulty of the tone-detection task and intensity of noise by means of cross-modality matching (CMM). Vibration-synchronous activity in the electrocardiogram was eliminated by a subtraction-technique. Noise caused an attenuation of the N1 and P2 amplitudes and prolongation of P3 latencies. The WBV did not cause systematic ERP effects. Condition B was associated with higher N1 and smaller P3 amplitudes. The factor "condition" had a significant effect on the peak latencies of P3 to target stimuli and the task difficulty judged by CMM. Both effects exhibited significant linear increases in the sequence of conditions A, B, C, D. For the evaluation of exposure conditions at work, it can be suggested that noise has a strong systematic effect which can be enhanced by WBV.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1992

Mismatch negativity in event-related potentials to auditory stimuli as a function of varying interstimulus interval.

The mismatch negativity, isolated as a component of the event-related brain potential elicited by deviant auditory stimuli, was suggested by Näätänen (1984) as an indirect measure of the inferred neuronal representation of standard stimuli. The purpose of the present study was to determine the duration of the neuronal representation by varying the interstimulus intervals of 1, 6, and 10 seconds within experimental blocks. Mismatch negativities were found to be elicited by deviant stimuli (1500-Hz tones, sequential probability 10%) following standard stimuli (1000-Hz tones) with interstimulus intervals of 1, 6, and 10 s as well. The results suggest a duration of neuronal representation of at least 10 s. The within-block variation of interstimulus interval, the rather low temporal probability of deviants, and their large frequency deviance might explain the present results contradicting earlier findings that suggested a shorter duration of that neuronal representation.

Adult↗
PubMed1992

[The P300 component of the event-related brain potential in a short-term memory paradigm].

In numerous investigations the P300-component of the event-related-brain-potential (ERP) has proved a valid indicator of memory activities. The present study explores the amplitude of the P300 in an isolated short term memory task with variant difficulties. In two experiments the reproduction of senseless memory material was examined using the categories "syllables" and "consonants". One syllable was thereby synonymous with the so-called "chunk" which represents a subjective unit arising from grouping of memory material. The results show a significant increase in P300-amplitude in a line with memory load in both categories. On the contrary there is no significant difference in the amplitude of P300 between the two categories. These results suggest that the costs for storing one syllable are comparable with those for one consonant.

Adult↗
PubMed1990

Changes in auditory evoked brain potentials during ultra-low frequency whole-body vibration of man or of his visual surround.

Auditory evoked brain potentials (AEP) were recorded from nine healthy male subjects during three types of condition: A - subject and visual field stationary; B - subject vibrated (z-axis, 0.6 Hz, 1.85 ms-2 rms), visual field stationary; C - subject stationary, visual field vibrated (as for B). The visual surround was confined to a checkerboard pattern in front of the subject. Auditory stimuli (1000 Hz, 86 dB, interstimulus interval 7 s) were delivered via headphones to evoke AEP. Vibration-synchronous activity in the EEG was eliminated by a subtraction technique. In comparison with condition A, conditions B and C caused an attenuation of P2 and N1P2 components of AEP together with an increased latency of N1. Effects of conditions B and C did not differ. Direct vestibular stimulation and mechanisms specific for whole-body vibration were rejected as modes of action. The AEP-changes and the subjective evaluation of experimental conditions, arousal and performance, as well as symptoms of kinetosis (motion sickness) suggest a sensory mismatch, leading to a "latent kinetosis" with de-arousal, as the dominating mechanism by which the processing of information was affected. This suggestion was supported by an additional pilot study. Under real working conditions a similar effect can be expected during relative motion between the driver and his visual surround, i.e. even with perfect vibro-isolation of the driver's seat.

Adult↗
PubMed1990

The effect of low-frequency whole-body vibration under different visual conditions on auditory evoked potentials.

Auditory evoked brain potentials (AEP) were recorded from 9 healthy males during sinusoidal whole-body vibration (WBV) in the longitudinal (+/- az) direction with 0.6 Hz, 1.85 ms-2rms (F1), 1.01 Hz, 4.27 ms-2rms (F2) and without WBV (F3) under 3 visual conditions--homogeneous bright visual field (B), normal vision (N), and complete darkness (D). The sequences of the different experimental conditions were arranged according to a 9 X 9 Latin Square design. A subtraction technique was used to eliminate vibration-synchronous activity from the EEG. The N1 and N1P2 amplitudes decreased during F1 and F2, compared to F3. The latencies of N1 and P2 increased during F1 and F2. The effects of F1 and F2 did not differ. The visual conditions exhibited no systematic effect on the AEP. The results suggest (1) F1 and F2 to be equivalent exposure conditions and (2) the dominance of vestibular-auditory interactions, compared with visual-auditory ones.

Acoustic Stimulation↗
PubMed1990

Amplitude variations in P300 component due to unpredictable stepwise change of stimulus probability.

The present study investigates whether the amplitude of the P300 in 'normal' subjects adapts to unexpected changes in global stimulus probability. The adaptation level (AL) metrics (in terms of Helson's [1964] theory) was applied to explain the variations in the P300 amplitude. In an oddball paradigm the probability of the deviant tone (target 1000 Hz, 80 dB, 50 ms) occurring randomly in a train of standard ones (non-target 1100 Hz, 80 dB, 50 ms) was changed in a stepwise way from 0.5 to 0.3 and then to 0.1 in 3 blocks without interruption of the stimulus presentation. Two experiments were performed. In the first one the subjects did not receive any prior information about the changes in the stimulus probability, whereas in the second experiment they were aware of such changes. The task always required the subject to silently count the deviants. EEG was recorded monopolarly from Fz, Cz and Pz in a total of 15 subjects. The block averaged P300 increased monotonically with probability, the increase being larger in Expt. II. In contrast to the block averaged P300, the variations in the P300 amplitude following the abrupt change in probability showed a non-linear dependency. On the basis of the AL a simulation of the time course of the P300 variations with probability was performed and a clear similarity between the simulated P300 and the experimental data was found. Some properties of the AL model are discussed.

Acoustic Stimulation↗
PubMed1990

[The history of the concept stress].

The historical roots of the term are treated as well as the story of Selye's theory of biological stress as a nonspecific response of the body. In the discussion of preceding approaches to describe processes which today one would name stress, the importance of Francois Magendie and John Brown as precursors is accentuated. Additionally, neurophysiological and psychological aspects are discussed.

Animals↗
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↗
PubMed1989

The P300 amplitude of the event-related brain potential indicates changes within a frame-of-reference.

The starting point of this study was the fact that investigations in the frame-of-reference research were mostly performed on the behavioural level. The present study aimed at studying behaviour of P300 amplitude of the event-related brain potential in a frame-of-reference investigation. Ten healthy volunteers participated in the investigation. Test material consisted of horizontal bars of different lengths presented successively on a screen. Each bar (serial stimulus) was preceded by a prestimulus (anchor) of constant length. Each serial stimulus was to be evaluated according to a 9 step rating scale. There were no significant differences in the overt length judgements of the serial stimuli depending on the 3 different anchor lengths. However, the mean P300 amplitude increased with growing dissimilarity between the length of the anchor and serial stimulus length. Thus, it is assumed that the adaptation level on the internal dimension of stimulus length, which was assumed to be influenced by the anchor stimuli, led to the different behaviour of P300 amplitude.

Adult↗
PubMed1989

[Evaluation of activities in computer-supported work places from the viewpoint of occupational physiology].

Evaluation of strain resulting from mental load in computer workplaces requires a psychophysiological approach. A complex valuation of various factors (well-being, physiological parameters, parameters of performance) is essential. Vegetative parameters correlate in a non-specific way with mental strain. On the other hand, the electrical brain activity reveals specific reactions to information processing. Actual trends of psychophysiological evaluation of mental strain are discussed as well as some conclusions for practical questions.

Brain↗
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↗
PubMed1988

The late positive component of the ERP and adaptation-level theory.

Relationships between the P300 component of the event-related potential (ERP) and processes of evaluation and categorization of events have been demonstrated in numerous investigations. On the other hand, these same processes have also been studied extensively by means of rating scale procedures within the framework of the psychological Adaptation-Level Theory. Recently, it has been suggested that the P300 amplitude reflects the distance between the adaptation level and the event that elicits the ERP. In this study we explored this suggestion by examining the effects of stimulus categorization on P300. Seven healthy adult subjects had to judge the length of five letter strings which were presented equiprobably in a randomized sequence. The ERPs (Fz, Cz, Pz derivations) elicited by string presentation were selectively averaged according to the five categories of string length. U-shaped trends of P300 amplitude changes were found. Minimum amplitudes were elicited by strings of medium length consistent with the inferred adaptation level. The data provide further evidence that P300 amplitude reflects the mental distance to adaptation level.

Adaptation, Physiological↗
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

P300 and anticipated task difficulty.

Recently, it has been shown that P300 measures depend on stimulus evaluation processes. This paper explores the effect of messages informing about the degree of difficulty of subsequent tasks on the P300 component. Ten healthy volunteers were asked to solve mental arithmetic tasks of graduated difficulty. The degree of difficulty was announced by messages which preceded the tasks and which were used as P300 eliciting stimuli. Measurements of the amplitude and latency of P300 components from 3 brain regions (Fz, Cz, Pz) were collected selectively for each category of task difficulty announced. Subjective ratings of difficulty and the frequency of errors confirmed the monotonic increase of task difficulty from categories I to VI. The mean P300 amplitude in categories I-VI showed a U-shaped trend, i.e. the highest amplitude occurred in the extreme categories 'extremely easy' and 'very difficult'. No significant effect of stimulus categories on P300 peak latencies was found. It is concluded that the P300 amplitude reflects an evaluation in the sense of distance judgements on an internal scale which in this study concerned the task difficulty.

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↗