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Klaus Fiedler

Publications and source records attributed to Klaus Fiedler.

13 recordsLinked to original sources
PubMed2006

Mood states modulate activity in semantic brain areas during emotional word encoding.

It is controversially discussed whether or not mood-congruent recall (i.e., superior recall for mood-congruent material) reflects memory encoding processes or reduces to processes during retrieval. We therefore investigated the neurophysiological correlates of mood-dependent memory during emotional word encoding. Event-related potentials (ERPs) were recorded while participants in good or bad mood states encoded words of positive and negative valence. Words were either complete or had to be generated from fragments. Participants had to memorize words for subsequent recall. Mood-congruent recall tended to be largest in good mood for generated words. Starting at 200 ms, mood-congruent ERP effects of word valence were obtained in good, but not in bad mood. Only for good mood, source analysis revealed valence-related activity in ventral temporal cortex and for generated words also in prefrontal cortex. These areas are known to be involved in semantic processing. Our findings are consistent with the view that mood-congruent recall depends on the activation of mood-congruent semantic knowledge during encoding. Incoming stimuli are more readily transformed according to stored knowledge structures in good mood particularly during generative encoding tasks. The present results therefore show that mood-congruent memory originates already during encoding and cannot be reduced to strategic processes during retrieval.

Adult↗
PubMed2006

Inflation of conditional predictions.

The authors report 7 experiments indicating that conditional predictions--the assessed probability that a certain outcome will occur given a certain condition--tend to be markedly inflated. The results suggest that this inflation derives in part from backward activation in which the target outcome highlights aspects of the condition that are consistent with that outcome, thus supporting the plausibility of that outcome. One consequence of this process is that alternative outcomes are not conceived to compete as fully as they should. Another consequence is that prediction inflation is resistant to manipulations that induce participants to consider alternative outcomes to the target outcome.

Adolescent↗
PubMed2006

Does decision quality (always) increase with the size of information samples? Some vicissitudes in applying the law of large numbers.

Adaptive decision making requires that contingencies between decision options and their relative assets be assessed accurately and quickly. The present research addresses the challenging notion that contingencies may be more visible from small than from large samples of observations. An algorithmic account for such a seemingly paradoxical effect is offered within a satisficing-choice framework. Accordingly, a choice is only made when the sample contingency describing the relative evaluation of the 2 options exceeds a critical threshold. Small samples, because of the high dispersion of their sampling distribution, facilitate above-threshold contingencies. Across a broad range of parameters, the resulting small-sample advantage in terms of hits is stronger than their disadvantage in false alarms. Computer simulations and experiments support the model predictions. The relative advantage of small samples is most apparent when information loss is low, when the threshold is high relative to the ecological contingency, and when the sampling process is self-truncated.

Algorithms↗
PubMed2006

Nonproportional sampling and the amplification of correlations.

A theoretical analysis shows that sample correlations between two binary variables will be inflated when the frequency distributions of the two variables are flatter (i.e., closer to equal frequencies for the two values) in the sample than in the population. A correlation-assessment study in which participants were free to choose their own sample revealed an overwhelming preference for samples that included roughly the same number of observations for the two values of dichotomous variables, irrespective of their actual distribution in the population. Subjective estimates of observed correlations followed the sample correlations--which were inflated, as predicted--more closely than the true correlations. People's sampling behavior thus resembles that of a research designer who maximizes the chance of detecting a relationship, at the cost of diminished accuracy in estimating its strength.

Data Interpretation, Statistical↗
PubMed2005

Priming trait inferences through pictures and moving pictures: the impact of open and closed mindsets.

A newly developed paradigm for studying spontaneous trait inferences (STI) was applied in 3 experiments. The authors primed dyadic stimulus behaviors involving a subject (S) and an object (O) person through degraded pictures or movies. An encoding task called for the verification of either a graphical feature or a semantic interpretation, which either fit or did not fit the primed behavior. Next, participants had to identify a trait word that appeared gradually behind a mask and that either matched or did not match the primed behavior. STI effects, defined as shorter identification latencies for matching than nonmatching traits, were stronger for S than for O traits, after graphical rather than semantic encoding decisions and after encoding failures. These findings can be explained by assuming that trait inferences are facilitated by open versus closed mindsets supposed to result from distracting (graphical) encoding tasks or encoding failures (involving nonfitting interpretations).

Cognition↗
PubMed2004

Effectivity of heparin in assisted reproduction.

Disturbances of the embryo-maternal interaction, i.e. impaired implantation, are seen in only a minor fraction of couples. These malfunctions become evident as recurrent spontaneous abortions (RSA), or repetitive implantation failure (RIF) in cases with IVF or ICSI procedures. The antiphospholipid syndrome (APL) is the only consensus-defined syndrome associated with RSA (anticardiolipin antibodies and/or lupus anticoagulant plus clinical symptoms). Since antiphospholipid antibodies directly interfere with hemostasis (increased coagulation), heparin is an established treatment option in these cases resulting in unequivocal benefits. There is no defined antibody syndrome in RIF even if it may be assumed that it exists. Conclusive evidence for a benefit of heparin (and aspirin) in this situation is lacking as well. However, the majority of investigations including our own experience indicate that anticoagulation may be useful. Besides the extensively studied anticardiolipin antibodies, other - by far less thoroughly investigated - antiphospholid antibodies have been described. So far it is unclear if heparin may exert positive effects in women carrying these antibodies. Autoreactive immune processes may also become apparent by the emergence of further antibodies, such as antinuclear (ANA), thyreoglobulin (TGA) and thyreoperoxidase antibodies (TPO) etc. However, there is no established definition of a syndrome associated with these antibodies, TGA and TPO probably being the most relevant. - Most studies in this area including our own experience indicate that heparin may be a useful. The detection or autoantibodies per se is probably not of pathophysiological relevance if there is no ongoing pathological activation of the immune system. However, an acute autoimmune response associated with irregular antibodies may represent the pathophysiological basis of a reproductive autoimmune failure syndrome. In these cases, immune-equilibrating interventions appear to be more appropriate than heparin therapy. - Coagulation disorders, namely thrombophilia, are a frequent cause of RSA and probably RIF as well, the most relevant being antithrombin deficiency, Factor V Leiden and prothrombin mutations. Deficiencies of protein S, protein C and factor XII and XIII are of minor importance. There is a varying degree of evidence for a benefit of heparin/aspirin in these syndromes. Heparin not only reduces the abortion rate but also lowers the risk for developmental retardation, premature birth and preeclampsia. - The effects of heparin are not restricted to anticoagulation. It is directly or indirectly (e.g. via heparan sulfate proteoglycans or heparin-binding EGF) involved in the adhesion of the blastocyst to the endometrial epithelium and the subsequent invasion. Actually, prolonged heparin treatment (14 days) resulted in an increased pregnancy rate in our patient population. Shorter courses of heparin where not effective.

Abortion, Habitual↗
PubMed2004

LDL transcytosis by protein membrane diffusion.

Endothelial cell (EC) cultures of different, selected vascular beds and/or organs were screened for receptor-mediated transport of proteins with a semipermeable filter assay. In SVEC4-10 cells, a mouse lymphoid endothelial cell line, orosomucoid, albumin, insulin and LDL were transcytosed from the apical (luminal) to basal (abluminal) side by a receptor-mediated pathway. Specific LDL transcytosis involved transport of intact LDL. A pathway of degradation of LDL and basal release involved vesicles in transport to lysosomes and amino acid merocrine secretion. This newly described transcellular passage of LDL via lysosomes, as well as the standard pathway, were reduced to 70% by PEG(50)-cholesterol (PEG-Chol). Combined results of temperature-dependence analysis and PEG(50)-cholesterol sensitivity show that two pathways contribute to general LDL transcellular passage. We suggest a mechanism of domain hopping by protein membrane diffusion of receptors as the pathway for intact LDL delivery. Based on theoretical considerations we propose that active transport by protein membrane diffusion can be facilitated by an organizational structure of lipid microdomains and polar cellular organization.

Animals↗
PubMed2004

Caveolae: biochemical analysis.

Caveolae appear in a multitude of processes encompassing growth regulation and trafficking. We demonstrate the abundant presence of ESA/reggie-1/flotillin-2, ATP synthase beta subunit and annexin V in endothelial caveolae by immunopurification of caveolae from vascular endothelial membrane. Five proteins are abundant in a caveolin-1 protein complex, analyzed by sucrose gradient velocity sedimentation following octyl-beta-D-glucopyranoside extraction. Caveolin-1 alpha interacts with caveolin-1beta, caveolin-2, actin, the microsomal form of NADH cytochrome B5 reductase and ESA/reggie-1/flotillin-2 as shown by co-immunoprecipitation. We propose the concept that ATP biosynthesis in caveolae regulates mechanosignaling and is induced by membrane depolarization and a proton gradient. Pressure stimuli and metabolic changes may trigger gene regulation in endothelial cells, involving a nuclear conformer of caveolin-1, shown here with an epitope-specific caveolin-1 antibody, and immediate response of ion channel activity, regulated by ESA/reggie-1/flotillin-2.

Animals↗
PubMed2004

Pseudocontingencies.

In 3 experiments, the authors explored a contingency illusion termed pseudocontingency (PC) that produces logically unwarranted but potentially useful inferences. PCs arise when bivariate contingencies are inferred from univariate distributions via heuristic alignment processes. For example, in the absence of information about the co-occurrence of TV habits and aggressive behavior within a school class, when the prevalence of both attributes is high, a teacher may infer a positive PC as if students who often watch TV were highly aggressive. Throughout 3 experiments, predictions of the level of 1 variable from the level of another served as a measure of PCs. The illusion could be evoked reliably whether information about target attributes was presented successively or simultaneously, whether common-cause or common-effect models were activated, and whether attributes involved 2 or more levels. The discussion centers on the cognitive processes underlying PCs and their origin and adaptive value.

Aggression↗
PubMed2004

Tools, toys, truisms, and theories: some thoughts on the creative cycle of theory formation.

Theory creation underlies the basic laws of evolution, calling for both random variation (loosening) and critical selection processes (tightening). Theory construction requires support of both components. However, whereas psychology has created a refined methodology for the tightening stage, attempts to understand the loosening stage of the creative cycle are conspicuously missing. I propose that both aspects of the creative cycle of theory formation can be acquired and exercised playfully, through distinct loosening and tightening games. I outline the rules of these games and illustrate them with examples from contemporary research.

Altruism↗
PubMed2003

Sperm retrieval procedures and intracytoplasmatic spermatozoa injection with epididymal and testicular sperms.

INTRODUCTION: Male infertility caused by azoospermia due to non-reconstructable obstruction or non-obstructive azoospermia can be treated by microsurgical epididymal aspiration (MESA) or testicular sperm extraction (TESE) followed by an intracytoplasmatic spermatozoa injection (ICSI). MATERIAL AND METHODS: From 9/93 to 6/01, we carried out 1,025 ICSI procedures with aspirated epididymal or testicular sperms in 684 cases. 163 ICSI cycles were performed with epididymal sperms and 862 ICSI cycles with testicular sperms or spermatids. The TESE was carried out by open biopsy, frequently in a multilocular technique. The aspirated spermatozoas were used after cryopreservation (frozen) or immediately after aspiration (fresh). RESULTS: 538 patients had obstructive azoospermia or ejaculation failure. In 487 cases the underlying cause of azoospermia was an impaired spermatogenesis, following maldescensus testis, chemotherapy, radiotherapy, or caused by Sertoli-cell-only syndrome, a genetic disorder or an unknown etiology. The transfer rates, pregnancy rates and birth rates per ICSI cycle showed no statistically significant differences between testicular and epididymal sperms in the cases of seminal obstruction (28% average birth rates in both cases). However, highly significant was the difference in birth rates with regard to the underlying cause of infertility. In contrast, in treating non-obstructive azoospermia we observed a birth rate of 19% per cycle. In all patient groups the birth rate with fresh spermatozoas did not differ from those with cryopreserved spermatozoa. 40% of patients after multilocular TESE showed clinical signs of testicular lesion. CONCLUSION: The underlying cause of azoospermia is the most important factor for the outcome of ICSI using epididymal and testicular sperms. In cases of non-obstructive azoospermia, the pregnancy rate is low compared with the results in cases of obstructive azoospermia. There is no difference between fresh and cryopreserved sperms. TESE with ICSI is the most efficient treatment of azoospermia caused by hypergonadotropic hypogonadism. The morbidity of the TESE procedure is highly relevant and must be considered if this technique is indicated.

Adult↗
PubMed2003

Inductive reasoning and judgment interference: experiments on Simpson's paradox.

In a series of experiments on inductive reasoning, participants assessed the relationship between gender, success, and a covariate in a situation akin to Simpson's paradox: Although women were less successful then men according to overall statistics, they actually fared better then men at either of two universities. Understanding trivariate relationships of this kind requires cognitive routines similar to analysis of covariance. Across the first five experiments, however, participants generalized the disadvantage of women at the aggregate level to judgments referring to the different levels of the covariate, even when motivation was high and appropriate mental models were activated. The remaining three experiments demonstrated that Simpson's paradox could be mastered when the salience of the covariate was increased and when the salience of gender was decreased by the inclusion of temporal cues that disambiguate the causal status of the covariate.

Adult↗