Teaching older adults to use retrieval practice improves their self-regulated learning.

Retrieval practice can reduce associative memory deficits for older adults but they underutilize this potent learning tool during self-regulated learning. The current experiment investigated whether teaching older adults to use retrieval practice more can improve their self-regulated learning. Younger and older adults made decisions about when to study, how often to engage in retrieval practice, and when to stop learning a list of medication-side effect pairs. Some younger and older adults received instructions before learning that emphasized the mnemonic benefits of retrieval practice over restudying material and described how to schedule retrieval practice to learn to a goal criterion level. This minimal intervention was effective for improving both younger and older adults' associative memory. These data indicate that a simple strategy for improving older adults self-regulated learning is to provide them with instructions that teach them how to use criterion learning to schedule their retrieval practice for to-be learned material.

Exploring the Role of Attentional Reorienting in the Reactive Effects of Judgments of Learning on Memory Performance.

Making judgments of learning (JOLs) while studying related word pairs can enhance performance on tests that rely on cue-target associations (e.g., cued recall) compared to studying alone. One possible explanation for this positive JOL reactivity effect is that the prompt to make JOLs, which typically occurs halfway through the presentation of each pair, may encourage learners to devote more attention to the pair during the second half of the encoding episode, which may contribute to enhanced recall performance. To investigate this idea, an online sample of participants (Experiment 1) and undergraduate students (Experiment 2) studied a set of moderately related word pairs (e.g., dairy-cow) in preparation for a cued recall test. Some participants made JOLs for each pair halfway through the presentation, whereas other participants did not. Also, some participants were presented with a fixation point halfway through the presentation, whereas other participants were not. The goal of this fixation point was to simulate the possible "reorienting" effect of a JOL prompt halfway through each encoding episode. In both an unsupervised online context and a supervised laboratory context, cued recall performance was higher for participants who made JOLs compared to those who did not make JOLs. However, presenting a fixation point halfway through the presentation of each pair did not lead to reactive effects on memory. Thus, JOLs are more effective than a manipulation that reoriented participants to the word pairs in another way (i.e., via a fixation point), which provides some initial evidence that positive reactivity for related pairs is not solely driven by attentional reorienting during encoding.

Protocol to perform dynamic microfluidic single-cell cultivation of C. glutamicum.

Here, we present a protocol for the design, fabrication, and usage of a polydimethylsiloxane (PDMS)-based chip for dynamic microfluidic single-cell cultivation of Corynebacterium glutamicum. We describe steps for flow profile establishment and biological preparation. We then detail time-lapse imaging to observe reactions of C. glutamicum to repeated environmental changes in the range of seconds. This system can be adapted to other organisms with a cell wall and soluble non-gaseous environmental factors like nutrients. For complete details on the use and execution of this protocol, please refer to Täuber et al..1.

Does Interactive Imagery Influence the Reactive Effect of Judgments of Learning on Memory?

Making judgments of learning (JOLs) while studying is a useful tool for students to evaluate the status of their learning. Additionally, in associative learning contexts, JOLs can directly benefit learning when the to-be-learned information is related. One explanation for this reactive effect is that making JOLs strengthens the associative relationship, leading to enhanced memory performance when a test relies on that relationship (e.g., cued-recall tests). In the present research, we evaluated whether having students make interactive mental images-another strategy that can increase the strength of a cue-target relationship-impacts the reactive effect of JOLs on learning. Students studied word pairs that were related and unrelated. Half of the students were instructed to form a mental image of the words interacting, whereas the other half were not. Additionally, in each group half of the students made a JOL for each pair, whereas half did not. Following a short delay, students completed a cued-recall test. Consistent with prior research, students who made JOLs remembered more related word pairs than did students who did not. By contrast, students who made JOLs recalled fewer unrelated word pairs than did students who did not. Moreover, although students who formed interactive images demonstrated enhanced memory relative to students who did not, interactive imagery did not impact the reactive effect of JOLs. These outcomes are informative for existing theory of JOL reactivity. Specifically, JOLs may only benefit learning of associative information when it has a pre-existing semantic relationship (e.g., related word pairs) and not when that that relationship is created by the learner (e.g., by forming interactive images).

Judgments of learning enhance recall for category-cued but not letter-cued items.

Making immediate judgments of learning (JOLs) during study can influence later memory performance, with a common outcome being that JOLs improve cued-recall performance for related word pairs (i.e., positive reactivity) and do not impact memory for unrelated pairs (i.e., no reactivity). The cue-strengthening hypothesis proposes that JOL reactivity will be observed when a criterion test is sensitive to the cues used to inform JOLs (Soderstrom et al., Journal of Experimental Psychology: Learning, Memory, and Cognition, 41 (2), 553-558, 2015). Across four experiments, we evaluated this hypothesis with category pairs (e.g., A type of gem - Jade) and letter pairs (e.g., Ja - Jade). Participants studied a list comprised of both pair types, made (or did not make) JOLs, and completed a cued-recall test (Experiments 1a/b). The cue-strengthening hypothesis predicts greater positive reactivity for category pairs than for letter pairs, because making a JOL strengthens the relationship between the cue and target, which is more beneficial for material with an a priori semantic relationship. Outcomes were consistent with this hypothesis. We also evaluated and ruled out alternative explanations for this pattern of effects: (a) that they arose due to overall differences in recall performance for the two pair types (Experiment 2); (b) that they would also occur even when the criterion test is not sensitive to the cues used to inform JOLs (Experiment 3); and (c) that JOLs only increased memory strength for the targets (Experiment 4). Thus, the current experiments rule out plausible accounts of reactivity effects and provide further, converging evidence for the cue-strengthening hypothesis.

Emerging Trends in Research on Self-Regulated Learning and Implications for Education: An Introduction to the Special Issue.

Students in higher education face a multitude of challenges when gaining and refining their knowledge [...].

Reliable cell retention of mammalian suspension cells in microfluidic cultivation chambers.

Microfluidic cultivation, with its high level of environmental control and spatio-temporal resolution of cellular behavior, is a well-established tool in today's microfluidics. Yet, reliable retention of (randomly) motile cells inside designated cultivation compartments still represents a limitation, which prohibits systematic single-cell growth studies. To overcome this obstacle, current approaches rely on complex multilayer chips or on-chip valves, which makes their application for a broad community of users infeasible. Here, we present an easy-to-implement cell retention concept to withhold cells inside microfluidic cultivation chambers. By introducing a blocking structure into a cultivation chamber's entrance and nearly closing it, cells can be manually pushed into the chamber during loading procedures but are unable to leave it autonomously in subsequent long-term cultivation. CFD simulations as well as trace substance experiments confirm sufficient nutrient supply within the chamber. Through preventing recurring cell loss, growth data obtained from Chinese hamster ovary cultivation on colony level perfectly match data determined from single-cell data, which eventually allows reliable high throughput studies of single-cell growth. Due to its transferability to other chamber-based approaches, we strongly believe that our concept is also applicable for a broad range of cellular taxis studies or analyses of directed migration in basic or biomedical research.

Microfluidic single-cell scale-down systems: introduction, application, and future challenges.

Performance losses during the scaling-up of bioprocesses from the laboratory to the production scale are common obstacles caused by the formation of concentration gradients in bioreactors. To overcome these obstacles, so-called scale-down bioreactors are used to analyze selected large-scale conditions and are one of the most important predictive tools for the successful transfer of bioprocesses from the lab to the industrial scale. In this regard, cellular behavior is usually measured as an averaged value, neglecting possible cell-to-cell heterogeneity within the culture. In contrast, microfluidic single-cell cultivation (MSCC) systems offer the possibility of understanding cellular processes on a single-cell level. To date, most MSCC systems have a limited choice of cultivation parameters that are not representative of bioprocess-relevant environmental conditions. Herein, we critically review recent advances in MSCC that allow the cultivation and analysis of cells under dynamic (bioprocess-relevant) environmental conditions. Finally, we discuss what technological advances and efforts are needed to bridge the gap between current MSCC systems and the use of these systems as single-cell scale-down devices.

Students' decisions to switch between categories or stay within them are related to practice classification performance.

How exemplars are ordered - blocked or interleaved - can play a critical role in later classification performance. Even so, when students self-regulate their learning, they typically block their study by choosing to stay within the same category on subsequent trials. Our goal was to evaluate the degree to which such decisions to stay within a category are influenced by performance on the previous practice trial. In five experiments, participants learned to classify categories of rocks by completing practice classification trials, receiving feedback, and making decisions about what to study on the next practice trial. The rate of stay choices was influenced by feedback type, a preceding familiarity trial, and location in the list. Most importantly, stay rates were low following correct classification demonstrating a preference to interleave study. By contrast, stay rates substantially increased following incorrect classification. Thus, practice classification performance and subsequent study decisions during complex categorical learning tasks can be strongly related.

Coupling Cell Size Regulation and Proliferation Dynamics of C. glutamicum Reveals Cell Division Based on Surface Area.

Single cells actively coordinate growth and division to regulate their size, yet how this size homeostasis at the single-cell level propagates over multiple generations to impact clonal expansion remains fundamentally unexplored. Classical timer models for cell proliferation (where the duration of the cell cycle is an independent variable) predict that the stochastic variation in colony size will increase monotonically over time. In stark contrast, implementing size control according to adder strategy (where on average a fixed size added from cell birth to division) leads to colony size variations that eventually decay to zero. While these results assume a fixed size of the colony-initiating progenitor cell, further analysis reveals that the magnitude of the intercolony variation in population number is sensitive to heterogeneity in the initial cell size. We validate these predictions by tracking the growth of isogenic microcolonies of Corynebacterium glutamicum in microfluidic chambers. Approximating their cell shape to a capsule, we observe that the degree of random variability in cell size is different depending on whether the cell size is quantified as per length, surface area, or volume, but size control remains an adder regardless of these size metrics. A comparison of the observed variability in the colony population with the predictions suggests that proliferation matches better with a cell division based on the cell surface. In summary, our integrated mathematical-experimental approach bridges the paradigms of single-cell size regulation and clonal expansion at the population levels. This innovative approach provides elucidation of the mechanisms of size homeostasis from the stochastic dynamics of colony size for rod-shaped microbes.

Do Domain Knowledge and Retrieval Practice Predict Students' Study Order Decisions?

Learning complex concepts is necessary for student success, but it is often challenging. Learning such concepts can be influenced by students' study order choices during learning to switch to a new category (interleaved study order) or stay within the same category (blocked study order). Students often prefer stay decisions during learning and make relatively few switch decisions; however, an open question is whether students' switch decisions are related to their level of prior knowledge in the domain and the learning strategy they use (retrieval practice versus study). To examine these relationships, we recruited undergraduate students from an introductory geology course. Prior to the course modules on rock classification, students self-rated their knowledge, took a prior knowledge test, classified rock exemplars by completing study or retrieval practice trials, and made study order choices. Students then completed assignments and attended lectures in their geology course on igneous, sedimentary, and metamorphic rocks. Next, students self-rated their knowledge, took a new prior knowledge test, completed study or retrieval practice trials, made study order decisions, took final classification tests, and self-reported beliefs about study order choices. Even though students' knowledge increased after course modules on rock identification, and most students believed that domain knowledge impacts study decisions, prior knowledge did not predict students' switch decisions. In contrast, students who completed retrieval practice trials made substantially more switch decisions (i.e., interleaved study) than did students who completed study trials.

Microfluidic single-cell scale-down bioreactors: A proof-of-concept for the growth of Corynebacterium glutamicum at oscillating pH values.

In large-scale bioreactors, gradients in cultivation parameters such as oxygen, substrate, and pH result in fluctuating cell environments. pH fluctuations were identified as a critical parameter for bioprocess performance. Traditionally, scale-down systems at the laboratory scale are used to analyze the effects of fluctuating pH values on strains and thus process performance. Here, we demonstrate the application of dynamic microfluidic single-cell cultivation (dMSCC) as a novel scale-down system for the characterization of Corynebacterium glutamicum growth using oscillating pH conditions as a model stress factor. A detailed comparison between two-compartment reactor (two-CR) scale-down experiments and dMSCC was performed for one specific pH oscillation between reference pH 7 (~8 min) and disturbed pH 6 (~2 min). Similar reductions in growth rates were observed in both systems (dMSCC 21% and two-CR 27%) compared to undisturbed cultivation at pH 7. Afterward, systematic experiments at symmetric and asymmetric pH oscillations, between pH ranges of 4-6 and 8-11 and different intervals from 1 to 20 min, were performed to demonstrate the unique application range and throughput of the dMSCC system. Finally, the strength of the dMSCC application was demonstrated by mimicking fluctuating environmental conditions of a putative large-scale bioprocess, which is difficult to conduct using two-CRs.

People hold mood-congruent beliefs about memory but do not use these beliefs when monitoring their learning.

Contemporary theories of metacognitive monitoring propose that beliefs play a critical role in monitoring of learning. Even so, recent evidence suggests that beliefs are not always sufficient to impact people's monitoring. In seven experiments, we explored people's beliefs about the impact of mood and item valence on memory and whether people use their beliefs about these cues when monitoring their learning. Participants expressed mood-congruent beliefs (Experiments 1, 6, and 7). That is, they believed people in a negative mood would remember more negative items than positive and neutral items. To evaluate whether they use this belief when monitoring their learning, participants studied emotional (positive and negative) and neutral pictures (Experiments 2 and 3) or words (Experiments 4, 5, and 7), made a judgment of learning (JOL) for each, and completed a free-recall test. In Experiments 2-5, participants completed the learning task while in a negative or neutral mood. The negative mood was induced with an established mood induction procedure. In contrast to the belief-based hypothesis, participants did not make mood-congruent JOLs; JOLs were not influenced by mood. By contrast, JOLs were consistently higher for emotional relative to neutral items. Thus, although participants demonstrated a mood-congruent belief, they did not use this belief when monitoring their learning. These outcomes demonstrate that simply having a belief about a person-centered cue (e.g., a belief about the impact of a person's mood on memory) is not sufficient for that belief to impact monitoring of learning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Older and younger adults' revision of health misconceptions.

Although ample younger adult research has detailed effective strategies for revising misconceptions, research with older adults is less extensive. Older adults may be less able to correct errors in knowledge due to age-related changes in cognition, but it is also possible that older adults' revision of misconceptions has been limited by methodologies which do not provide adequate support for correction. In two experiments, we examined how older and younger adults revise health-related misconceptions when provided with cognitive support in the form of explicit detailed feedback and an immediate test. Older and younger adults in Experiment 1 answered true/false health statements, received feedback with a detailed explanation of the correct response, took an additional test on the same statements immediately following the initial test, and completed a final test 1-week later. Older and younger adults corrected a similar proportion of misconceptions immediately and maintained most of those revisions across a 1-week delay. In Experiment 2, older adults corrected the same proportion of misconceptions on the final test regardless of whether or not they received a test immediately following feedback. Overall, older adults revised health misconceptions as effectively as did younger adults but variables influencing correction (e.g., belief in feedback) may differ.

How to Perform a Microfluidic Cultivation Experiment-A Guideline to Success.

As a result of the steadily ongoing development of microfluidic cultivation (MC) devices, a plethora of setups is used in biological laboratories for the cultivation and analysis of different organisms. Because of their biocompatibility and ease of fabrication, polydimethylsiloxane (PDMS)-glass-based devices are most prominent. Especially the successful and reproducible cultivation of cells in microfluidic systems, ranging from bacteria over algae and fungi to mammalians, is a fundamental step for further quantitative biological analysis. In combination with live-cell imaging, MC devices allow the cultivation of small cell clusters (or even single cells) under defined environmental conditions and with high spatio-temporal resolution. Yet, most setups in use are custom made and only few standardised setups are available, making trouble-free application and inter-laboratory transfer tricky. Therefore, we provide a guideline to overcome the most frequently occurring challenges during a MC experiment to allow untrained users to learn the application of continuous-flow-based MC devices. By giving a concise overview of the respective workflow, we give the reader a general understanding of the whole procedure and its most common pitfalls. Additionally, we complement the listing of challenges with solutions to overcome these hurdles. On selected case studies, covering successful and reproducible growth of cells in MC devices, we demonstrate detailed solutions to solve occurring challenges as a blueprint for further troubleshooting. Since developer and end-user of MC devices are often different persons, we believe that our guideline will help to enhance a broader applicability of MC in the field of life science and eventually promote the ongoing advancement of MC.

Growth Response and Recovery of Corynebacterium glutamicum Colonies on Single-Cell Level Upon Defined pH Stress Pulses.

Bacteria respond to pH changes in their environment and use pH homeostasis to keep the intracellular pH as constant as possible and within a small range. A change in intracellular pH influences enzyme activity, protein stability, trace element solubilities and proton motive force. Here, the species Corynebacterium glutamicum was chosen as a neutralophilic and moderately alkali-tolerant bacterium capable of maintaining an internal pH of 7.5 ± 0.5 in environments with external pH values ranging between 5.5 and 9. In recent years, the phenotypic response of C. glutamicum to pH changes has been systematically investigated at the bulk population level. A detailed understanding of the C. glutamicum cell response to defined short-term pH perturbations/pulses is missing. In this study, dynamic microfluidic single-cell cultivation (dMSCC) was applied to analyze the physiological growth response of C. glutamicum to precise pH stress pulses at the single-cell level. Analysis by dMSCC of the growth behavior of colonies exposed to single pH stress pulses (pH = 4, 5, 10, 11) revealed a decrease in viability with increasing stress duration w. Colony regrowth was possible for all tested pH values after increasing lag phases for which stress durations w were increased from 5 min to 9 h. Furthermore, single-cell analyses revealed heterogeneous regrowth of cells after pH stress, which can be categorized into three physiological states. Cells in the first physiological state continued to grow without interruption after pH stress pulse. Cells in the second physiological state rested for several hours after pH stress pulse before they started to grow again after this lag phase, and cells in the third physiological state did not divide after the pH stress pulse. This study provides the first insights into single-cell responses to acidic and alkaline pH stress by C. glutamicum.

Activation of Nrf2 by Electrophiles Is Largely Independent of the Selenium Status of HepG2 Cells.

Selenoenzymes, whose activity depends on adequate selenium (Se) supply, and phase II enzymes, encoded by target genes of nuclear factor erythroid 2-related factor 2 (Nrf2), take part in governing cellular redox homeostasis. Their interplay is still not entirely understood. Here, we exposed HepG2 hepatoma cells cultured under Se-deficient, Se-adequate, or Se-supranutritional conditions to the Nrf2 activators sulforaphane, cardamonin, or diethyl maleate. Nrf2 protein levels and intracellular localization were determined by immunoblotting, and mRNA levels of Nrf2 target genes and selenoproteins were assessed by qRT-PCR. Exposure to electrophiles resulted in rapid induction of Nrf2 and its enrichment in the nucleus, independent of the cellular Se status. All three electrophilic compounds caused an enhanced expression of Nrf2 target genes, although with differences regarding extent and time course of their induction. Whereas Se status did not significantly affect mRNA levels of the Nrf2 target genes, gene expression of selenoproteins with a low position in the cellular "selenoprotein hierarchy", such as glutathione peroxidase 1 (GPX1) or selenoprotein W (SELENOW), was elevated under Se-supplemented conditions, as compared to cells held in Se-deficient media. In conclusion, no major effect of Se status on Nrf2 signalling was observed in HepG2 cells.

Development and application of a cultivation platform for mammalian suspension cell lines with single-cell resolution.

In bioproduction processes, cellular heterogeneity can cause unpredictable process outcomes or even provoke process failure. Still, cellular heterogeneity is not examined systematically in bioprocess research and development. One reason for this shortcoming is the applied average bulk analyses, which are not able to detect cell-to-cell differences. In this study, we present a microfluidic tool for mammalian single-cell cultivation (MaSC) of suspension cells. The design of our platform allows cultivation in highly controllable environments. As a model system, Chinese hamster ovary cells (CHO-K1) were cultivated over 150 h. Growth behavior was analyzed on a single-cell level and resulted in growth rates between 0.85 and 1.16 day-1 . At the same time, heterogeneous growth and division behavior, for example, unequal division time, as well as rare cellular events like polynucleation or reversed mitosis were observed, which would have remained undetected in a standard population analysis based on average measurements. Therefore, MaSC will open the door for systematic single-cell analysis of mammalian suspension cells. Possible fields of application represent basic research topics like cell-to-cell heterogeneity, clonal stability, pharmaceutical drug screening, and stem cell research, as well as bioprocess related topics such as media development and novel scale-down approaches.

dMSCC: a microfluidic platform for microbial single-cell cultivation of Corynebacterium glutamicum under dynamic environmental medium conditions.

In nature and in technical systems, microbial cells are often exposed to rapidly fluctuating environmental conditions. These conditions can vary in quality, e.g., the existence of a starvation zone, and quantity, e.g., the average residence time in this zone. For strain development and process design, cellular response to such fluctuations needs to be systematically analysed. However, the existing methods for physically imitating rapidly changing environmental conditions are limited in spatio-temporal resolution. Hence, we present a novel microfluidic system for cultivation of single cells and small cell clusters under dynamic environmental conditions (dynamic microfluidic single-cell cultivation (dMSCC)). This system enables the control of nutrient availability and composition between two media with second to minute resolution. We validate our technology using the industrially relevant model organism Corynebacterium glutamicum. The organism was exposed to different oscillation frequencies between nutrient excess (feasts) and scarcity (famine). The resulting changes in cellular physiology, such as the colony growth rate and cell morphology, were analysed and revealed significant differences in the growth rate and cell length between the different conditions. dMSCC also allows the application of defined but randomly changing nutrient conditions, which is important for reproducing more complex conditions from natural habitats and large-scale bioreactors. The presented system lays the foundation for the cultivation of cells under complex changing environmental conditions.

Dynamic Environmental Control in Microfluidic Single-Cell Cultivations: From Concepts to Applications.

Microfluidic single-cell cultivation (MSCC) is an emerging field within fundamental as well as applied biology. During the last years, most MSCCs were performed at constant environmental conditions. Recently, MSCC at oscillating and dynamic environmental conditions has started to gain significant interest in the research community for the investigation of cellular behavior. Herein, an overview of this topic is given and microfluidic concepts that enable oscillating and dynamic control of environmental conditions with a focus on medium conditions are discussed, and their application in single-cell research for the cultivation of both mammalian and microbial cell systems is demonstrated. Furthermore, perspectives for performing MSCC at complex dynamic environmental profiles of single parameters and multiparameters (e.g., pH and O2 ) in amplitude and time are discussed. The technical progress in this field provides completely new experimental approaches and lays the foundation for systematic analysis of cellular metabolism at fluctuating environments.