The benefit of expecting no conflict--Stronger influence of self-generated than cue-induced conflict expectations on Stroop performance

Sequential modulation of across-task congruency in the serial reaction time task

While detrimental effects of dual-tasking on the acquisition and usage of sequence knowledge in the Serial Reaction Time Task (SRTT) have been attributed to the integration of regularly and randomly sequenced events, direct evidence for across-task integration has been scarce. In two experiments, we paired two spatial tasks: A visual-manual SRTT (serial reaction time task) of length 4 and a two-choice task with random order of stimuli. We reasoned that across-task integration might result in SRTT- and two-choice task events being stored and retrieved together. Therefore, RT might be influenced by current congruency as well as by whether it is repeated or altered from the congruency level encountered for this SRTT event in the last loop of the sequence. We observed such a modulation in two experiments, suggesting that across-task integration indeed takes place and that the detrimental effect of dual-tasking on sequence learning is, at least in parts, based on across-task integration.

Differential effects of cue-based and sequence knowledge-based predictability on multitasking performance

Everyday multitasking often is characterized by predictable sequences. While such sequential regularities are present in setups using the Serial Reaction Time Task (SRTT), many laboratory studies on dual-tasking performance use random sequences of stimuli in either of the two tasks. In the current study, following single-task training on the SRTT, participants completed trials where they were confronted with an additional visual-manual task with either a random (Experiment 1) or a partially predictable (Experiment 2) stimulus sequence. In the SRTT, we cued participants with respect to which of the four stimulus options were yet to occur (before a new round with all four options would start). We randomly mixed a sequence to be practiced with random sequences of the same length and with the same constraint. Thus, we were able to vary predictability of upcoming stimuli (from chance to 100%) as well as sequence knowledge (practiced vs. random sequence) in order to assess how cueing and sequence knowledge, as two potential bases of prediction, would affect performance in single- and dual-tasking. Results suggest that both cueing and sequence knowledge-based prediction can lead to shorter RTs in dual-tasking. In previous studies, the disruption of sequence learning by adding a task with a random stimulus sequence has been linked to the effects of automatic prediction between events in the two tasks. In line with these studies, dual-task performance did not impede usage of sequence knowledge when a task with a predictable (rather than random) sequence of stimuli was added to the SRTT.

Integrated externally and internally generated task predictions jointly guide cognitive control in prefrontal cortex

Cognitive control proactively configures information processing to suit expected task demands. Predictions of forthcoming demand can be driven by explicit external cues or be generated internally, based on past experience (cognitive history). However, it is not known whether and how the brain reconciles these two sources of information to guide control. Pairing a probabilistic task-switching paradigm with computational modeling, we found that external and internally generated predictions jointly guide task preparation, with a bias for internal predictions. Using model-based neuroimaging, we then show that the two sources of task prediction are integrated in dorsolateral prefrontal cortex, and jointly inform a representation of the likelihood of a change in task demand, encoded in frontoparietal cortex. Upon task-stimulus onset, dorsomedial prefrontal cortex encoded the need for reactive task-set adjustment. These data reveal how the human brain integrates external cues and cognitive history to prepare for an upcoming task.

[Neurocognitive function of children with acute lymphoblastic leukemia and long-term disease-free survival and related influencing factors]

OBJECTIVE

To investigate the neurocognitive function of children with acute lymphoblastic leukemia (ALL) and long-term disease-free survival and related influencing factors.

METHODS

A total of 40 ALL children with long-term disease-free survival were enrolled as study group, and 40 healthy children were enrolled as control group. The Chinese Wechsler Intelligence Scale for Children (C-WISC), continuous performance test (CPT), and Stroop test software were used for the evaluation of all children. Neurocognitive function was compared between groups and influencing factors were analyzed.

RESULTS

Compared with the control group, the study group had significantly lower full intelligence quotient, verbal intelligence quotient, and performance intelligence quotient in C-WICS (P<0.05) and significantly higher numbers of mistakes and misses in CPT (P<0.05). There were no significant differences in the numbers of correct answers, mistakes, and misses of word-color consistency between the study group and the control group (P>0.05), while the study group had significantly higher numbers of mistakes and misses of word-color contradiction and irrelevance (P<0.05). The total dose of high-dose methotrexate and ALL risk classification were associated with the reduction in intelligence quotient, and children's younger age at diagnosis of ALL was associated with the higher numbers of misses and mistakes. Girls tended to have a significantly lower performance intelligence quotient than boys (P<0.05).

CONCLUSIONS

ALL children with long-term disease-free survival have neurocognitive impairment, which may be associated with the dose of chemotherapeutic drugs, age at diagnosis, and sex.

Tied to expectations: Predicting features speeds processing even under adverse circumstances

When participants predict the upcoming stimulus in a randomized choice reaction task, a match between prediction and stimulus increases processing speed at a level similar to that observed in cueing studies with highly valid cues. This might be taken to suggest that people cannot help but fully use their self-generated, verbalized predictions for preparing task processing. Thus, we tested how flexibly participants can control formation and implementation of predictions. In Experiment 1, we varied validity and response-relevance of predictions. We observed that prediction effects on RT can be boosted by increasing validity, but prevail under adverse circumstances. This was not the case in a control group who read rather than predicted the feature words, suggesting that the effect was specific to predictions as such. Experiment 2 provided further evidence for limited control of participants over implementing and forming predictions. Participants were provided with practice on stimuli occurring with varying frequency, but neither learned to strategically choose predictions to maximize the number of match trials, nor did they reduce the amount of prediction-based preparation when predicting an infrequent stimulus. As sequential aftereffects of prediction match did not vary with validity, they were identified as an independent effect of verbalizing a response-relevant stimulus feature. The results are consistent with the view that the predicted stimulus feature is represented in the focus of attention in working memory and that the amount of implementation can be subject to weighting.