Cue-target contingencies modulate voluntary orienting of spatial attention: dissociable effects for speed and accuracy

Voluntary orienting of spatial attention is typically investigated by visually presented directional cues, which are called predictive when they indicate where the target is more likely to appear. In this study, we investigated the nature of the potential link between cue predictivity (the proportion of valid trials) and the strength of the resulting covert orienting of attention. Participants judged the orientation of a unilateral Gabor grating preceded by a centrally presented, non-directional, color cue, arbitrarily prompting a leftwards or rightwards shift of attention. Unknown to them, cue predictivity was manipulated across blocks, whereby the cue was only predictive for either the first or the second half of the experiment. Our results show that the cueing effects were strongly influenced by the change in predictivity. This influence differently emerged in response speed and accuracy. The speed difference between valid and invalid trials was significantly larger when cues were predictive, and the amplitude of this effect was modulated at the single trial level by the recent trial history. Complementary to these findings, accuracy revealed a robust effect of block history and also a different time-course compared with speed, as if it mainly mirrored voluntary processes. These findings, obtained with a new manipulation and using arbitrary non-directional cueing, demonstrate that cue-target contingencies strongly modulate the way attention is deployed in space

Modulating proactive cognitive control by reward:Differential anticipatory effects of performance contingent and non-contingent rewards

The present study investigated the influences of two different forms of reward presentation in modulating cognitive control. In three experiments, participants performed a flanker task for which one-third of trials were precued for a chance of obtaining a reward (reward trials). In Experiment 1, a reward was provided if participants made the correct response on reward trials, but a penalty was given if they made an incorrect response on these trials. The anticipation of this performance-contingent reward increased response speed and reduced the flanker effect, but had little influence on the sequential modulation of the flanker effect after incompatible trials. In Experiment 2, participants obtained a reward randomly on two-thirds of the precued reward trials and were given a penalty on the remaining one-third, regardless of their performance. The anticipation of this non-contingent reward had little influence on the overall response speed or flanker effect, but reduced the sequential modulation of the flanker effect after incompatible trials. Experiment 3 also used performance non-contingent rewards, but participants were randomly penalized more often than they were rewarded; non-contingent penalty had little influence on the sequential modulation of the flanker effect. None of the three experiments showed a reliable influence of the actual acquisition of rewards on task performance. These results indicate anticipatory effects of performance-contingent and non-contingent rewards on cognitive control with little evidence of aftereffects

Implicit Learning of Stimulus Regularities Increases Cognitive Control

In this study we aim to examine how the implicit learning of statistical regularities of successive stimuli affects the ability to exert cognitive control. In three experiments, sequences of flanker stimuli were segregated into pairs, with the second stimulus contingent on the first. Response times were reliably faster for the second stimulus if its congruence tended to match the congruence of the preceding stimulus, even though most participants were not explicitly aware of the statistical regularities (Experiment 1). In contrast, performance was not enhanced if the congruence of the second stimuli tended to mismatch the congruence of the first stimulus (Experiment 2). The lack of improvement appears to result from a failure of learning mismatch contingencies (Experiment 3). The results suggest that implicit learning of inter-stimulus relationships can facilitate cognitive control

AREVA NP's enhanced accident-tolerant fuel developments: Focus on Cr-coated M5 cladding

AREVA NP (Courbevoie, Paris, France) is actively developing several enhanced accident-tolerant fuels cladding concepts ranging from near-term evolutionary (Cr-coated zirconium alloy cladding) to long-term revolutionary (SiC/SiC composite cladding) solutions, relying on its worldwide teams and partnerships, with programs and irradiations planned both in Europe and the United States.The most advanced and mature solution is a dense, adherent chromium coating on zirconium alloy cladding, which was initially developed along with the CEA and EDF in the French joint nuclear R&D program. The evaluation of the out-of-pile behavior of the Cr-coated cladding showed excellent results, suggesting enhanced reliability, enhanced operational flexibility, and improved economics in normal operating conditions. For example, because chromium is harder than zirconium, the Cr coating provides the cladding with a significantly improved wear resistance. Furthermore, Cr-coated samples exhibit extremely low corrosion kinetics in autoclave and prevents accelerated corrosion in harsh environments such as in water with 70 ppm Li leading to improved operational flexibility.Finally, AREVA NP has fabricated a physical vapor deposition prototype machine to coat full-length cladding tubes. This machine will be used for the manufacturing of full-length lead test rods in commercial reactors by 2019. Keywords: Accident-Tolerant Fuels, Cladding, Cr Coating, Physical Vapor Depositio

Repetition or alternation of context influences sequential congruency effect depending on the presence of contingency

The sequential congruency effect (SCE) is defined as the decrease in the congruency effect following incongruent trials compared to congruent trials. The effect of context repetition on the SCE was investigated in four experiments. In all the experiments, dynamic visual white noise was used as the contextual feature, and the number of congruent and incongruent trials was equal. In Experiments 1 and 2, by using eight-value Flanker and Stroop tasks, and excluding stimulus- and response-feature repetitions from the analysis, a SCE was observed in both context repetition and alternation conditions. In Experiment 3, using a two-value Flanker task, all trials consisted of stimulus- and response-feature repetitions, and a SCE was only observed in the context repetition condition. In Experiment 4, we used a four-value Flanker task, which enabled half of the trials to be partial/complete repetitions and the other half to be complete alternations. A SCE was observed in both context repetition and alternation conditions irrespective of the stimulus- and response-feature repetitions. This pattern of results suggested that the effects of context repetition on the SCE are subject to a number of factors including stimulus- and response-feature repetitions and contingency biases. When contingency information exists, the presence of stimulus- and response-feature repetitions was no longer effective in yielding effects of context repetition on the SCE. These findings suggest that the usage of information registered in episodic event representations including stimulus-, response- and contextual-features, control parameters and contingency biases results from interactions of a complex pattern of mechanisms, yet to be further explored