The centrosome protein AKNA regulates neurogenesis via microtubule organization.

The expansion of brain size is accompanied by a relative enlargement of the subventricular zone during development. Epithelial-like neural stem cells divide in the ventricular zone at the ventricles of the embryonic brain, self-renew and generate basal progenitors1 that delaminate and settle in the subventricular zone in enlarged brain regions2. The length of time that cells stay in the subventricular zone is essential for controlling further amplification and fate determination. Here we show that the interphase centrosome protein AKNA has a key role in this process. AKNA localizes at the subdistal appendages of the mother centriole in specific subtypes of neural stem cells, and in almost all basal progenitors. This protein is necessary and sufficient to organize centrosomal microtubules, and promote their nucleation and growth. These features of AKNA are important for mediating the delamination process in the formation of the subventricular zone. Moreover, AKNA regulates the exit from the subventricular zone, which reveals the pivotal role of centrosomal microtubule organization in enabling cells to both enter and remain in the subventricular zone. The epithelial-to-mesenchymal transition is also regulated by AKNA in other epithelial cells, demonstrating its general importance for the control of cell delamination.

Simulating conversations: A Markov chain model of a central speaker's mnemonic influence over a group of communicating listeners.

Through their selective rehearsal, Central Speakers can reshape collective memory in a group of listeners, both by increasing accessibility for mentioned items (shared practice effects) and by decreasing relative accessibility for related but unmentioned items (socially shared retrieval induced forgetting, i.e., SSRIF). Subsequent networked communication in the group can further modify these mnemonic influences. Extant empirical work has tended to examine such downstream influences on a Central Speaker's mnemonic influence following a relatively limited number of interactions - often only two or three conversations. We develop a set of Markov chain simulations to model the long-term dynamics of such conversational remembering across a variety of group types, based on reported empirical data. These models indicate that some previously reported effects will stabilize in the long-term collective memory following repeated rounds of conversation. Notably, both shared practice effects and SSRIF persist into future steady states. However, other projected future states differ from those described so far in the empirical literature, specifically: the amplification of shared practice effects in communicational versus solo remembering non-conversational groups, the relatively transient impact of social (dis)identification with a Central Speaker, and the sensitivity of communicating networks to much smaller mnemonic biases introduced by the Central Speaker than groups of individual rememberers. Together, these simulations contribute insights into the long-term temporal dynamics of collective memory by addressing questions difficult to tackle using extant laboratory methods, and provide concrete suggestions for future empirical work.

Overestimating the intensity of negative feelings in autobiographical memory: evidence from the 9/11 attack and COVID-19 pandemic.

When recalling autobiographical events, people not only retrieve event details but also the feelings they experienced. The current study examined whether people are able to consistently recall the intensity of past feelings associated with two consequential and negatively valenced events, i.e. the 9/11 attack (N = 769) and the COVID-19 pandemic (N = 726). By comparing experienced and recalled intensities of negative feelings, we discovered that people systematically recall a higher intensity of negative feelings than initially reported - overestimating the intensity of past negative emotional experiences. The COVID-19 dataset also revealed that individuals who experienced greater improvement in emotional well-being displayed smaller biases in recalling their feelings. Across both datasets, the intensity of remembered feelings was correlated with initial feelings and current feelings, but the impact of the current feelings was stronger in the COVID-19 dataset than in the 9/11 dataset. Our results demonstrate that when recalling negative autobiographical events, people tend to overestimate the intensity of prior negative emotional experiences with their degree of bias influenced by current feelings and well-being.

A day that America will remember: flashbulb memory, collective memory, and future thinking for the capitol riots.

ABSTRACTThis study explores the topics of flashbulb memory, collective identity, future thinking, and shared representations for a public event. We assessed the memories of the Capitol Riots, which happened in Washington DC, on 6 January 2021. Seventy Belgian and seventy-nine American citizens participated in an online study, in which they freely recalled the unfolding of Capitol Riots and answered questions regarding their memory. Inter-subjects similarity of recalled details was analysed using a schematic narrative template (i.e., the event, the causes and the consequences). Results revealed that representations of the event, and its causes were more similar among Belgians compared to Americans, whereas Americans' representations of the consequences showed more similarity than Belgians'. Also, as expected, Americans reported more flashbulb memories (FBMs) than Belgians. The analysis underlined the importance of rehearsal through media and communication in FBM formation. This research revealed a novel relation between FBM and future representations. Regardless of national identity, participants who formed an FBM were more likely to think that the event would be remembered in the future, that the government should memorialise the event, and that a similar attack on the Capitol could happen in the future compared to participants who did not form FBM.

Changes over 10 years in the retelling of the flashbulb memories of the attack of 11 September 2001.

A flashbulb memory is a highly detailed and vivid autobiographical memory for the circumstances in which one first learned of a surprising, consequential and emotionally arousing event. How retelling of different features of a flashbulb memory changes over time is not totally understood. Moreover, little is known about how the emotional feeling experienced by individuals when they learned about the event modulates these changes. In this study, we explored changes over time in American individuals' retelling of their flashbulb memories of the terrorist attack of 11 September 2001. We conducted textual analysis of 824 testimonies collected from the same 206 individuals 1 week, 11, 25 and again 119 months after the attack. Results showed individuals were more likely to report temporal and emotional details in their retelling early after the event and spatial details in their long-term retelling. In addition, the intensity of emotions felt upon hearing the news about the attack influenced how individuals reported their flashbulb memories over time. Overall, this study provides further support for theories suggesting different rates of forgetting for different canonical features of emotional arousal events.

Remembering the big game: social identity and memory for media events.

Two studies examined how memories are formed around championship sporting events, which we classify as media events. The first study employed a test-retest methodology to assess how fans of a sport recall a championship sporting event. The second study examined how fans of specific sports teams recalled two championship sporting events in which their team either won or lost. Of particular interest was the emergence of a collective memory within fan communities. We assessed memory for the event itself (event memory), with an emphasis on the emergence of a collective memory, and memory for the context in which one experienced the event (personal circumstance memory). In contrast to fans of a sport more generally, fans of a particular team recalled events involving their team with detail, converged on collective memories, and provided personal circumstance memories that met the criteria for flashbulb memories. We discuss these results in the context of social identities and the elements involved in narratives of media events. Different types of fandom, our measure of social identity, uniquely influenced the collective memories formed for essential and ancillary elements of narratives surrounding championship sporting events.

Mutagenic cost of ribonucleotides in bacterial DNA.

Replicative DNA polymerases misincorporate ribonucleoside triphosphates (rNTPs) into DNA approximately once every 2,000 base pairs synthesized. Ribonucleotide excision repair (RER) removes ribonucleoside monophosphates (rNMPs) from genomic DNA, replacing the error with the appropriate deoxyribonucleoside triphosphate (dNTP). Ribonucleotides represent a major threat to genome integrity with the potential to cause strand breaks. Furthermore, it has been shown in the bacterium Bacillus subtilis that loss of RER increases spontaneous mutagenesis. Despite the high rNTP error rate and the effect on genome integrity, the mechanism underlying mutagenesis in RER-deficient bacterial cells remains unknown. We performed mutation accumulation lines and genome-wide mutational profiling of B. subtilis lacking RNase HII, the enzyme that incises at single rNMP residues initiating RER. We show that loss of RER in B. subtilis causes strand- and sequence-context-dependent GC → AT transitions. Using purified proteins, we show that the replicative polymerase DnaE is mutagenic within the sequence context identified in RER-deficient cells. We also found that DnaE does not perform strand displacement synthesis. Given the use of nucleotide excision repair (NER) as a backup pathway for RER in RNase HII-deficient cells and the known mutagenic profile of DnaE, we propose that misincorporated ribonucleotides are removed by NER followed by error-prone resynthesis with DnaE.

What's ours is yours: recall of history for lesser-known countries is guided by one's own national history.

The present studies examine how people recall history. Sometimes, certain national histories are well known and sometimes they are not. We propose that, under certain circumstances, culturally distinctive representations of typical national histories can be used to guide recall, particularly in cases where the history is not well known. We focus on three national samples with varied levels of knowledge about each history: Great Britain, India, and the United States. In Study 1, we establish typical historical event templates for each nation consisting of events that a large proportion of participants from each sample identify as important in a typical nation's history. We examine points of divergence between the different groups' typical event templates and the valences of these events. In Study 2, we test and find that, in conditions of less knowledge, participants tend to refer to particular historical events that coincide with events unique to their own group's typical history. In Study 3, we demonstrate that this effect can be found even when a group possesses a reasonable amount of knowledge about the target country. We conclude by discussing the implications in relation to how such a retrieval strategy might inform interpretations of events in the present.

Substrate Specificity for Bacterial RNases HII and HIII Is Influenced by Metal Availability.

We tested the activities of four predicated RNase H enzymes, including two RNase HI-type enzymes, in addition to RNase HII (RnhB) and RNase HIII (RnhC), on several RNA-DNA hybrid substrates with different divalent metal cations. We found that the two RNase HI-type enzymes, YpdQ and YpeP, failed to show activity on the three substrates tested. RNase HII and RNase HIII cleaved all the substrates tested, although the activity was dependent on the metal made available. We show that Bacillus subtilis RNase HII and RNase HIII are both able to incise 5' to a single ribonucleoside monophosphate (rNMP). We show that RNase HIII incision at a single rNMP occurs most efficiently with Mn2+, an activity we found to be conserved among other Gram-positive RNase HIII enzymes. Characterization of RNases HII and HIII with metal concentrations in the physiological range showed that RNase HII can cleave at single rNMPs embedded in DNA while RNase HIII is far less effective. Further, using metal concentrations within the physiological range, RNase HIII efficiently cleaved longer RNA-DNA hybrids lacking an RNA-DNA junction, while RNase HII was much less effective. Phenotypic analysis showed that cells with an rnhC deletion were sensitive to hydroxyurea (HU). In contrast, cells with an rnhB deletion showed wild-type growth in the presence of HU, supporting the hypothesis that RNases HII and HIII have distinct substrate specificities in vivo This work demonstrates how metal availability influences the substrate recognition and activity of RNases HII and HIII, providing insight into their functions in vivoIMPORTANCE RNase H represents a class of proteins that cleave RNA-DNA hybrids, helping resolve R-loops and Okazaki fragments, as well as initiating the process of ribonucleotide excision repair (RER). We investigated the activities of four Bacillus subtilis RNase H enzymes and found that only RNases HII and HIII have activity and that their substrate preference is dependent on metal availability. To understand the factors that contribute to RNase HII and RNase HIII substrate preference, we show that in the presence of metal concentrations within the physiological range, RNases HII and HIII have distinct activities on different RNA-DNA hybrids. This work provides insight into how RNases HII and HIII repair the broad range of RNA-DNA hybrids that form in Gram-positive bacteria.

Cultural and communicative memories: contrasting Argentina's 1976 coup d'état and the 2001 economic-political-social crisis.

Studies on collective memory have recently addressed the distinction between cultural and communicative memory as a way to understand how the source of a memory affects its structure or form. When a groups' memory is mediated by memorials, documentaries or any other cultural artifacts, collective memory is shaped by cultural memory. When it is based mostly in communication with other people, its source is communicative memory. We address this distinction by studying two recent events in Argentinean history: the 2001 economic-political-social crisis (communicative memory) and the 1976 coup (cultural memory). We also examine the political ideology and the type of memory involved in collective memory. The memory of the studied events may occur during the lifetime of the rememberer (Lived Memory) or refer to distant events (Distant Memory). 100 participants responded to a Free Recall task about the events of 2001 in Argentina. Narrative analysis allowed comparing these recalls with our 1976 study. Results show: 1) Cultural memories are more contextualised, more impersonal and less affective. 2) Communicative memories are more personal and affective. Study shows how collective memory form changes when it has a different prevalent source.

More to episodic memory than epistemic assertion: The role of social bonds and interpersonal connection.

Remembering is dynamically entangled in conversations. The communicative function of episodic memory can be epistemic, as suggested by Mahr & Csibra (M&C). However, remembering can have genuinely social functions, specifically, the creation or consolidation of interpersonal relationships. Autonoesis, a distinct feature of episodic memory, is more likely to have evolved in the service of social binding than of epistemic assertiveness.

Argentines' collective memories of the military Junta of 1976: differences and similarities across generations and ideology.

Although memories about a nation's past usually are semantic in nature, a distinction needs to be made between lived and distant semantic collective memories. The former refers to memories of community-relevant events occurring during the lifetime of the rememberer, whereas the latter to memories of distant events. Does the content of lived and distant semantic collective memories differ? Employing both free and cued recall, we examined the memories of younger and older Argentines of the Military Junta of 1976. We also examined the effects of political ideology. Content analysis indicated that (1) lived semantic collective memories were more likely to contain personal recollections than distant semantic collective memories, even though those with distant semantic collective memories could have incorporated memories of the parent's personal experience in their recollections, (2) lived semantic collective memories contained more causal statements, and (3) those on the Right with distant semantic collective memories were more likely to claim that they "Don't know" or offer positive accounts of the Junta, suggesting a need to "defend" the reputation of those on the Right. The results are discussed in terms of the goals and plans different generations might have when recollecting their nation's past.

Justifying atrocities: the effect of moral-disengagement strategies on socially shared retrieval-induced forgetting.

A burgeoning literature has established that exposure to atrocities committed by in-group members triggers moral-disengagement strategies. There is little research, however, on how such moral disengagement affects the degree to which conversations shape people's memories of the atrocities and subsequent justifications for those atrocities. We built on the finding that a speaker's selective recounting of past events can result in retrieval-induced forgetting of related, unretrieved memories for both the speaker and the listener. In the present study, we investigated whether American participants listening to the selective remembering of atrocities committed by American soldiers (in-group condition) or Afghan soldiers (out-group condition) resulted in the retrieval-induced forgetting of unmentioned justifications. Consistent with a motivated-recall account, results showed that the way people's memories are shaped by selective discussions of atrocities depends on group-membership status.

Episodic and semantic components of autobiographical memories and imagined future events in post-traumatic stress disorder.

Individuals with post-traumatic stress disorder (PTSD) tend to retrieve autobiographical memories with less episodic specificity, referred to as overgeneralised autobiographical memory. In line with evidence that autobiographical memory overlaps with one's capacity to imagine the future, recent work has also shown that individuals with PTSD also imagine themselves in the future with less episodic specificity. To date most studies quantify episodic specificity by the presence of a distinct event. However, this method does not distinguish between the numbers of internal (episodic) and external (semantic) details, which can provide additional insights into remembering the past and imagining the future. This study employed the Autobiographical Interview (AI) coding scheme to the autobiographical memory and imagined future event narratives generated by combat veterans with and without PTSD. Responses were coded for the number of internal and external details. Compared to combat veterans without PTSD, those with PTSD generated more external than internal details when recalling past or imagining future events, and fewer internal details were associated with greater symptom severity. The potential mechanisms underlying these bidirectional deficits and clinical implications are discussed.

Emotion language use in narratives of the 9/11 attacks predicts long-term memory.

Despite considerable cognitive neuroscience research demonstrating that emotions can influence the encoding and consolidation of memory, research has failed to demonstrate a relationship between self-reported ratings of emotions collected soon after a traumatic event and memory for the event over time. This secondary analysis of data from a multisite longitudinal study of memories of the September 11, 2001 terrorist attacks, asked the question of whether emotional language use could predict memory over time. In the 2 weeks following the 9/11 attacks, participants (N = 691; Mage = 36.8; 72% identifying as male; 76% identifying as white) wrote narratives about how they learned of the attacks and the impact of the attacks on them. Language features of these narratives were extracted using the Linguistic Inquiry Word Count program and used to predict three types of memory: (a) event memory accuracy, (b) flashbulb memory consistency, and (c) emotion memory consistency. These outcomes were assessed at the time of writing, 1, 3, and 10 years after the 9/11 attacks. Results of linear mixed-effects models indicate that greater use of negative emotion words in narratives predicts better event memory accuracy 3 and 10 years after the attacks and worse flashbulb memory consistency 10 years after the attacks. However, emotion word use does not predict emotion memory consistency across time. We also examine whether other exploratory linguistic predictors are associated with memory over time. These findings suggest that written language may serve as a potential early indicator of memory over time. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Remembering in conversations: the social sharing and reshaping of memories.

People constantly talk about past experiences. Burgeoning psychological research has examined the role of communication in remembering by placing rememberers in conversational settings. In reviewing this work, we first discuss the benefits of collaborative remembering (transactive memory and collaborative facilitation) and its costs (collaborative inhibition, information sampling biases, and audience tuning). We next examine how conversational remembering affects subsequent memory. Here, we address influences on listeners' memory through social contagion, resistance to such influences, and then retrieval/reexposure effects on either speaker or listener, with a focus on retrieval-induced forgetting. Extending the perspective beyond single interactions, we consider work that has explored how the above effects can spread across networks of several individuals. We also explore how a speaker's motive to form a shared reality with listeners can moderate conversational effects on memory. Finally, we discuss how these various conversational effects may promote the formation of collective memories.

Remembering President Barack Obama's inauguration and the landing of US Airways Flight 1549: a comparison of the predictors of autobiographical and event memory.

We examined and compared the predictors of autobiographical memory (AM) consistency and event memory accuracy across two publicly documented yet disparate public events: the inauguration of Barack Obama as the 44th president of the United States on January 20th 2009, and the emergency landing of US Airways Flight 1549, off the coast of Manhattan, on January 15th 2009. We tracked autobiographical and event memories for both events, with assessments taking place within 2½ weeks of both events (Survey 1), and again between 3½ and 4 months after both events (Survey 2). In a series of stepwise regressions we found that the psychological variables of recalled emotional intensity and personal importance/centrality predicted AM consistency and event memory accuracy for the inauguration. Conversely, the rehearsal variables of covert rehearsal and media attention predicted, respectively, AM consistency and event memory accuracy for the plane landing. We conclude from these findings that different factors may underlie autobiographical and event memory for personally and culturally significant events (e.g., the inauguration), relative to noteworthy, yet less culturally significant, events (e.g., the plane landing).

Collective mental time travel: Current research and future directions.

In this chapter, we will provide a review on the emerging psychological literature on collective mental time travel (MTT). Our review will focus on the cognitive aspects of remembering the collective past and imagining the collective future. We will explore factors such as specificity, phenomenal characteristics, content, and valence. We will also include brief overviews of cultural and social psychological research that is relevant to the topic of collective MTT. In these overviews, we will examine the research on narratives, collective continuity, collective angst, and human action. Three main themes will emerge from these discussions: the connection between collective past and future thinking, the differences between collective past and future thinking, and the role of goals, perceived agency, and collective action. We will integrate the findings of cognitive, cultural, and social psychological work through these three themes and offer ways to move collective MTT research forward.

Purification of functional Plasmodium falciparum tubulin allows for the identification of parasite-specific microtubule inhibitors.

Cytoskeletal proteins are essential for parasite proliferation, growth, and transmission, and therefore have the potential to serve as drug targets.1-5 While microtubules and their molecular building block αß-tubulin are established drug targets in a variety of cancers,6,7 we still lack sufficient knowledge of the biochemistry of parasite tubulins to exploit the structural divergence between parasite and human tubulins. For example, it remains to be determined whether compounds of interest can specifically target parasite microtubules without affecting the host cell cytoskeleton. Such mechanistic insights have been limited by the lack of functional parasite tubulin. In this study, we report the purification and characterization of tubulin from Plasmodium falciparum, the causative agent of malaria. We show that the highly purified tubulin is fully functional, as it efficiently assembles into microtubules with specific parameters of dynamic instability. There is a high degree of amino-acid conservation between human and P. falciparum α- and ß-tubulin, sharing approximately 83.7% and 88.5% identity, respectively. However, Plasmodium tubulin is more similar to plant than to mammalian tubulin, raising the possibility of identifying compounds that would selectively disrupt parasite microtubules without affecting the host cell cytoskeleton. As a proof of principle, we describe two compounds that exhibit selective toxicity toward parasite tubulin. Thus, the ability to specifically disrupt protozoan microtubule growth without affecting human microtubules provides an exciting opportunity for the development of novel antimalarials.

Knowledge of Chosen Family History and Depressive Symptoms in Sexual Minority Women.

Recent work on intergenerational memory has revealed a positive association between family of origin knowledge and wellbeing in adolescents. However, little is known about the generalizability of these data, as significantly less attention has focused on autobiographical memory sharing and wellbeing in historically marginalized communities. Given the high incidence of familial rejection and abandonment within the LGBTQIA + community, close relationships with individuals outside of one's family of origin, chosen families, often serve as an important source of social support. This study sought to examine the relationship between knowledge of a close non-family member and wellbeing among emerging adult sexual minority women (SMW) according to their gender presentation. A community sample from New York City comprised of heterosexual women (n = 50), masculine-presenting SMW (n = 50), and feminine presenting SMW (n = 50) completed measures associated with their knowledge of their family of origin, knowledge of a close non-family member, as well as self-reported measures of depression, emotion regulation, and socio-demographic questions. Family of origin knowledge was associated with lower levels of depression only among heterosexual women. However, heterosexual and SMW who knew more about their close non-family member reported lower levels of depression. Additionally, emotion regulation (cognitive reappraisals) mediated the relationship between knowing more about one's chosen family and lower depressive symptom severity among heterosexual women, but this relationship was only significant for SMW who were at least moderately open about their sexuality. These findings extend the literature on the benefits of memory sharing to historically marginalized communities by showing that memory sources outside of one's family of origin may be particularly important. Additionally, these data begin to shed light on potential mediating factors, such as emotion regulation and openness about one's sexual identity, that underlie the links between memory sharing and metrics of wellbeing. Taken together, in contexts in which there may not be opportunities to learn about family history from one's family of origin, it appears that access to stories from someone close outside of one's family is also associated with lower levels of depression.