The relation between response-specificity, S-R compatibility, foreperiod duration and muscle-tension in a target aiming task

Three experiments are reported aiming at a further understanding of the effect of response-specificity, operationalized as the degree of commonality of direction of movements. In a previous study, Spijkers (1987) has claimed that response-specificity affects the readiness of the motor system and is not related to response-selection processes. These suppositions were generally confirmed in experiments 1 and 2 respectively. Common to both experiments were the variables average movement velocity and response-specificity. In experiment 1 the effect of the additional variable foreperiod duration was found to interact with that of response-specificity, hereby confirming its expected relation to the muscular system. The effect of response-specificity did not interact with that of spatial S-R compatibility in the second experiment, but also failed to show a main effect. The third experiment examined the supposed relation of response-specificity more directly through manipulation of the muscle-tension of the responding limb. The predicted form of the interaction between the effect of response-specificity and muscle-tension was confirmed which provided additional evidence for the interpretation of response-specificity effects in terms of differential muscular activation.     

Structural Constraints on the Performance of Symmetrical Bimanual Movements with Different Amplitudes

In bimanual movements the amplitude of each hand's movement often depends on the concurrent amplitude of the other hand's movement such that both amplitudes become similar (amplitude coupling). We tested the hypothesis that the strength of amplitude coupling depends on the tempo of performance of a movement sequence, a hypothesis based on a model of bimanual coordination that holds that cross-talk occurs at the execution level as well as at the programming level. Subjects performed bimanual periodic arm movements on two digitizers. In nine conditions constant small, constant large, and alternating small and large amplitudes of each arm were orthogonally combined. Overall tempo was varied by instructing subjects to increase the tempo progressively by 10%. Clear tempo-dependent modulations of the amplitude were observed in movements with instructed constant amplitude when the other hand performed alternating amplitudes. The effect of the size of constant-amplitude movements on the mean amplitude of the other hand indicated cross-talk at the execution level. Cross-talk at the programming level was revealed by the dependence of the current amplitude on the change in the amplitude of the other hand in the preceding cycle. Finally, asymmetric cross-manual effects were observed.     

Time‐of‐day variation of visuo‐spatial attention

Time‐of‐day variation of visuo‐spatial attention in relation to body temperature and subjective arousal was assessed. At five different times of day, alertness, covert, and overt orienting of attention were assessed in fifteen healthy subjects. Based on previous studies reporting a tight coupling of alerting and orienting the present study investigates potential attentional asymmetries induced by diurnal variations of arousal. Both covert and overt orienting of attention improved in the course of the day. However, no asymmetries between left and right visual hemifields could be detected. Covert orienting additionally covaried with body temperature, indicating a quite close relation between the attentional arousal and orienting system. Conversely, overt orienting only improved due to repeated testing but did not correlate with body temperature suggesting a partial independence of both modes of attentional orienting. It can be assumed that due to limited diurnal variations of arousal in the participants and practice effects caused by repeated testing, no attentional asymmetries could be provoked.     

Intermanual cross-talk effects in unimanual choice reactions

Intermanual interactions originate at different levels of motor control. Interactions during specification of movement characteristics should affect reaction time for choice between left-hand and right-hand movements. In two experiments combinations of short and long target amplitudes for reversal movements of the left and right hand were cued with variable precueing intervals. Upon presentation of the response signal a unimanual left-hand or right-hand movement had to be produced. Reaction time was faster when same target amplitudes were precued than when different target amplitudes were. At short precueing intervals the longer reaction time with different target amplitudes (early effect) was accompanied by an amplitude assimilation: Short amplitudes were too long, and long amplitudes were too short. At longer precueing intervals the longer reaction time with different target amplitudes (late effect) was accompanied by a higher choice accuracy. These findings are taken to indicate a transient parametric coupling of amplitude specifications, which produces the early and the late effects by way of different mechanisms-namely different degrees of advance specification and generalized de-coupling, which affects the process of choice between hands.     

Parametric coupling and generalized decoupling revealed by concurrent and successive isometric contractions of distal muscles

In two experiments we examined the hypothesis of transient parametric coupling during the specification of peak forces of isometric contractions produced by the left and right hand. In the first experiment participants had to produce bimanual contractions with same and different target forces as rapidly as possible in response to an auditory signal; target forces were cued visually with variable cueing intervals. At short cueing intervals reaction times were longer when different peak forces had to be specified than when same peak forces were cued, and this reaction-time difference declined as the cueing interval was increased. Independent of the cueing interval intermanual correlations of peak forces, rise times, and reaction times were smaller in conditions with different peak forces than in those with same peak forces. In the second experiment imperative signals for left-hand and right-hand contractions were separated in time. Target forces for the first response were cued with variable cueing intervals, while for the second response the cues were presented simultaneously with the second imperative signal. Reaction time of the second response was longer when target forces for the two successive responses were different rather than same, and this reaction-time difference declined when the delay of the second signal was increased as well as when the cueing interval for the first response became longer. These results are consistent with the hypothesis of a transient cross-talk between concurrent processes of peak-force specifications; in addition they indicate generalization of the decoupling required to specify different peak forces concurrently to the specification of temporal response characteristics and to processes of response initiation.     

Static and phasic cross-talk effects in discrete bimanual reversal movements

The authors examined the hypothesis that the phasic and the static cross-talk effects found in bimanual movements with different target amplitudes originate at different functional levels of motor control, which implies that the effects can be dissociated experimentally. When the difference between the short and the long amplitudes assigned to the 2 hands of 12 participants was decreased, the static effect disappeared, In contrast, the phasic effect, which can be observed only at short preparation intervals, did not disappear; although it became smaller in absolute terms, in relative terms it did not. In addition, the authors compared the time course of amplitude variability and examined the correlation between left hand and right hand amplitudes. The disappearance of the phasic amplitude assimilation at increasing preparation intervals turned out to be delayed relative to the decline of the correlation between amplitudes. That finding suggests that the assimilation of mean amplitudes and the correlation between left hand and right hand amplitudes are not fully equivalent indicators of intermanual interactions, but may indicate different kinds of inter-limb coupling.     

The impact of violations on uncertainty and the consequences for attractiveness

This investigation aimed at extending past research on expectation violations by arguing that violations vary both in valance and in their influence on uncertainty and that the combination of valence and uncertainty states conjointly influences judgments of a violator's social attractiveness. In explaining the predicted variance in uncertainty following violations, a distinction is proposed between congruent violations (i.e., behaviors that are more intense instantiations of a previously displayed message) and incongruent violations (i.e., behaviors that are opposite in meaning from previously displayed messages). Five models for explaining violation effects are contrasted. Results (a) confirm that violations differ in their impact on uncertainty, (b) generally support the validity of the proposed distinction between congruent and incongruent violations, and show that the inclusion of uncertainty and valence in models of violation outcomes accounts for greater variance in social attraction than either one separately.     

Effects of sleep loss, time of day, and extended mental work on implicit and explicit learning of sequences

Tacit knowledge is part of many professional skills and can be studied experimentally with implicit-learning paradigms. The authors explored the effects of 2 different stressors, loss of sleep and mental fatigue, on implicit learning in a serial-response time (RT) task. In the 1st experiment, 1 night of sleep deprivation was shown to impair implicit but not explicit sequence learning. In the 2nd experiment, no impairment of both types of sequence learning was found after 1.5 hr of mental work. Serial-RT performance, in contrast, suffered from both stressors. These findings suggest that sleep deprivation induces specific risks for automatic, skill-based behavior that are not present in consciously controlled performance.     

浅析阿尔贝特·施韦泽的医学伦理人格

阿尔贝特·施韦泽作为20世纪西方社会中极具影响力的人物,他所主张的敬畏生命的伦理思想固然值得我们今天学习研究、发扬光大,而他作为一名著名医学家,他传奇智慧的人生中所进行的一系列医学实践活动,更是展示了他热爱生命、热爱人类、热爱医学、富有理想、淡泊名利、甘于奉献医学的高尚医学伦理人格、炽热的医学伦理情怀,更值得我们当今每一位医务工作者和在校医学生敬仰、学习。