Directed forgetting in pigeons

Pigeons performed a version of delayed matching-to-sample in which different postsample cues signaled different trial outcomes. Cues to remember (R cues) signaled the usual comparison stimuli. Cues to forget (F cues) signaled either cancellation of comparison stimuli (comparison-omission) or presentation of a sample-independent discrimination (comparison-substitution). As assessed by occasional probe trials, F cues decreased matching accuracy during comparison-omission more than during comparison-substitution. The loss in accuracy of matching in F-cue probes was directly related to length of delays during comparison-omission but not during comparison-substitution. Because trials generally terminated in reward during comparison-substitution but not during comparison-omission, these findings were interpreted as suggesting the importance of end-of-trial reinforcement for the maintenance of short-term memory.     

Directed forgetting in pigeons: Analysis of cue functions

In delayed matching-to-sample with pigeons, brief postsample cues signaled different trial outcomes. The normal comparison stimuli followed the cue to remember (R cue). In the comparison-omission procedure, comparison stimuli and reinforcement were omitted following the cue to forget (F cue). In the comparison-substitution procedure, comparison stimuli were replaced by a single stimulus and reinforcement for a single response following the F cue. Infrequent probe trials revealed that F cues disrupted matching, with the amount of accuracy loss dependent on the length of the cue-comparison delay. These results, however, were found only with the comparison-omission procedure (Experiment 1). Replacing the comparison stimuli with another simultaneous (unconditional) discrimination revealed no accuracy loss in F-cue probes (Experiment 2), even though choice latencies were again lengthened by F cues. These results suggest that, while the F cue interferes with performance at the time of a retention test by slowing choices, it also interferes with sample retention. Alternative models of the cuing effect and its apparent dependence on end-of-trial reward are outlined.     

Two sources of proactive interference in spatial working memory: Multiple effects of repeated trials on radial maze performance by rats

Rats were trained in 8- and 12-arm radial mazes. Each trial began with a study phase (forced choices of 4 arms). The trial ended after a 2-h delay in a test phase consisting of free choices among 8 arms; choices of the 4 arms not yet visited were correct (rewarded). Proactive interference (PI) was induced by an interference phase that occurred on some days 2 or 3 h prior to the study phase. In the PI-repetition condition, the interference phase consisted of forced choices of the 8 arms that were later presented in the study and test phases; in the PI-nonrepetition condition, the interference consisted of forced choices of the 4 arms that were correct during the test phase. Test-phase performance was most accurate in the No PI (single-trial) condition and least accurate in the PI-repetition condition. A second experiment showed that repetitions per se were not responsible for the PI; when the interference phase consisted only of choices of the same 4 arms later presented in the study phase, no PI was observed. These findings suggest two sources of PI. One source, measured by the difference between No PI and PI-nonrepetition conditions, appears to be a difficulty in discriminating the temporal order of visits to arms in the interference and study phases. The other source of PI, measured by the difference between the nonrepetition and repetition conditions, remains to be identified; some possibilities are discussed.     

Maps and inventories: Anchoring efforts to track student learning

Opportunities for students to learn what we wish them to are tucked in nooks and crannies of their college experience as much as they are in the obvious places. The author presents two strategies for revealing all the corners where learning occurs and those where it should but might be missing.     

Evaluating the effects of repeated reading and continuous reading using a standardized dosage of words read

Repeated reading (RR) is a common fluency intervention, but recent studies comparing RR to continuous reading (CR; i.e., wide reading) found no significant differences in effects. This prompts the question of whether the mechanism that improves skills is repeatedly reading portions of connected text, or simply reading connected text. The current study examined the differential effectiveness of RR and CR for increasing oral reading fluency rate (ORF) and comprehension of 40 students in second and third grades, randomly assigned to receive the RR or CR intervention. Students in both conditions received a standardized amount of practice (dosage) in the form of number of words read during each intervention session. All but two participants increased their ORF and there were no significant differences between groups on posttest ORF or broad comprehension. Moreover, students with the highest pretest scores made slightly more growth regardless of condition. Students in the RR group demonstrated significantly higher comprehension of practiced passages and students in the CR condition reported significantly higher levels of intervention acceptability. Implications for reading fluency intervention research and practice are discussed.     

Rational Higher-Order Belief Revision in Young Children

Belief revision can occur at multiple levels of abstraction, including lower-level and higher-order beliefs. It remains unclear, however, how conflicting evidence interacts with prior beliefs to encourage higher-order belief revision. This study explores how 4- and 5-year-olds (N = 96) respond to evidence that directly conflicts with their causal higher-order beliefs. When shown a single event that directly violated a strongly supported prior belief, preschoolers largely maintained their initial higher-order belief. However, when the prior belief was more weakly supported and the counterevidence was stronger, children changed their minds. These findings indicate that young children can revise their higher-order beliefs and, furthermore, do so depending on the strength of both the evidence and their prior beliefs.     

Induction of alternative fate other than default neuronal fate of embryonic stem cells in a membrane-based two-chambered microbioreactor by cell-secreted BMP4

Cell-secreted soluble factor signaling in a diffusion dominant microenvironment plays an important role on early stage differentiation of pluripotent stem cells invivo. In this study, we utilized a membrane-based two-chambered microbioreactor (MB) to differentiate mouse embryonic stem cells (mESCs) in a diffusion dominant microenvironment of the top chamber while providing enough nutrient through the bottom chamber. Speculating that accumulated FGF4 in the small top chamber will augment neuronal differentiation in the MB culture, we first differentiated mESCs for 8 days by using a chemically optimized culture medium for neuronal induction. However, comparison of cellular morphology and expression of neuronal markers in the MB with that in the 6-well plate (6WP) indicated relatively lower neuronal differentiation in the MB culture. Therefore, to investigate whether microenvironment in the MB facilitates non-neuronal differentiation, we differentiated mESCs for 8 days by using chemically defined basal medium. In this case, differentiated cell morphology differed markedly between the MB and 6WP cultures: epithelial sheet-like morphology in the MB, whereas rosette morphology in the 6WP. Expression of markers from the three germ layers indicated lower neuronal but higher meso- and endo-dermal differentiation of mESCs in the MB than the 6WP culture. Moreover, among various cell-secreted soluble factors, BMP4 expression was remarkably upregulated in the MB culture. Inhibition of BMP4 signaling demonstrated that enhanced effect of upregulated BMP4 was responsible for the prominent meso- and endo-dermal differentiation in the MB. However, in the 6WP, downregulated BMP4 had a minimal influence on the differentiation behavior. Our study demonstrated utilization of a microbioreactor to modulate the effect of cell-secreted soluble factors by autoregulation and thereby inducing alternative self-capability of mESCs. Understanding and implementation of autoregulation of soluble factors similar to this study will lead to the development of robust culture systems to control ESC behavior.     

Association between COMT Val158Met polymorphism and competition results of competitive swimmers

Recent studies have shown the contribution of genetic determinants to athletes’ physical ability. However, despite the fact that cognitive abilities like self-control and stress-tolerance influence athletes’ competitive performance, few studies to date have investigated the association between genetic polymorphism, which is linked to cognitive ability and athletic performance. The present study investigated the link between single-nucleotide polymorphisms (SNPs), which are known to exert influences on dopaminergic neural function and competitive performance of swimmers. The results have revealed superior competitive performance in competitive swimmers with Met allele of catechol-O-methyltransferase Val158Met polymorphism than those with Val/Val genotype. The investigated SNPs of DRD2 and DRD3 were not associated with swimmer’s competitive performance. This finding indicates that genetic polymorphism linked to cognitive ability influences the athletes’ performance.