Forgetting “Novel” but Not “Dragon”: The Role of Age of Acquisition on Intentional and Incidental Forgetting

Two experiments studied how the age at which words are acquired (Age of Acquisition, AoA) modulates forgetting. Experiment 1 employed the retrieval-practice paradigm to test the effect of AoA on the incidental forgetting that emerges after solving competition during retrieval (i.e., retrieval-induced forgetting, RIF). Standard RIF appeared with late-acquired words, but this effect disappeared with early-acquired words. Experiment 2 evaluated the effect of AoA on intentional forgetting by employing the list-method directed forgetting paradigm. Results showed a standard directed forgetting effect only when the to-be-forgotten words were late-acquired words. These findings point to the prominent role of AoA in forgetting processes.This research was supported by grants from the Spanish Ministry of Economy and Competitiveness (http://www.mineco.gob.es/portal/site/mineco/?lang_choosen=en) to AM (PSI2013-46033-P), TB (PSI2012-33625), and CJG-A (PSI2011-25797), and from the Ministry of Science (http://www.mineco.gob.es/portal/site/mineco/?lang_choosen=en) (EDU2008-01111) and the Andalusian Government (http://www.juntadeandalucia.es/) (P12-CTS-2369) to TB

The effect of interference on reactivation of spatial memories in reconsolidation model by using an innovative experimental paradigm in healthy young adults at the behavioral level

La mémoire déclarative est définie comme notre capacité à acquérir des faits et des événements qui font l'objet d'un souvenir conscient. Après la phase d'encodage, de nouvelles mémoires subissent des transformations hors ligne, qui permettent aux traces initialement labiles de se fixer dans la structure physique du cerveau; un processus appelé consolidation. Il existe également des preuves accumulées qu'une fois qu'une mémoire consolidée est réactivée ou récupérée, cette dernière passe par un processus de reconsolidation au cours duquel elle peut être dégradée, maintenue ou améliorée. Dans la présente étude, nous avons cherché à répondre à la question suivante: Les traces consolidées récupérées sont-elles susceptibles d'être perturbées par le même type d'information? Et quel serait l'effet de l'interférence sur différents tests de reconnaissance comparant les deux groupes. Méthode: Nous avons développé une tâche basée sur le travail de Sonni et al. (Sonni and Spencer 2015), où les sujets devaient apprendre à localiser 36 images d'objets du quotidien situées sur un écran d'ordinateur. 40 sujets en bonne santé (25,03 ± 3,66) ont participé à cette étude. Groupe 1: Interférence (20 sujets); Groupe 2: contrôle (20 sujets). Résultats: Nous avons constaté que l'administration de la matrice B après rappel de la première matrice (Groupe 1) interférait avec la reconsolidation de la mémoire, et augmentait ainsi significativement la quantité d'oubli observée lors de la reprise de la séance le Jour 3. En revanche, nous ne pouvions pas trouver un effet d'interférence dans le groupe de contrôle. Il y avait significativement plus de taux de fausses alarmes dans le groupe d'interférence. Nos résultats confirment l'hypothèse de reconsolidation de la mémoire déclarative, mais des travaux supplémentaires sont nécessaires pour déterminer si les substrats neuronaux et neurophysiologiques qui interviennent dans la reconsolidation sont identiques ou différents de ceux impliqués dans la consolidation.Declarative memory is defined as our capacity to acquire facts and events that are subject to conscious recollection. After the encoding phase, new memories undergo offline transformations, which allow the initially labile traces to become fixed into the physical structure of the brain; a process called consolidation. There is also accumulating evidence that once a consolidated memory is reactivated or retrieved, the latter goes through a reconsolidation process during which it can be degraded, maintained or enhanced. In the present study, we sought to answer the following question: Are retrieved consolidated traces susceptible to disruption by the same type of information? Method: We developed a task based on work by Sonni et al. (Sonni and Spencer 2015), in which subjects were required to learn the location of 36 everyday objects images located on a computer screen. 40 healthy subjects (25.03 ± 3.66) participated in this study. Group 1: Interference (20 subjects); Group 2: control (20 subjects). Results: We found that the administration of the matrix B after recall of the first matrix (Group 1) interfered with reconsolidation of the memory, and thus significantly increase the amount of forgetting seen in the retest session on Day 3. In contrast we could not find any interference effect in the control group. Our results confirm the reconsolidation hypothesis for declarative memory, but further work is needed to identify whether the neural and neurophysiological substrates mediating reconsolidation are the same or different from those involved during consolidation

Contributions of post-learning REM and NREM sleep to memory retrieval

It has become clear that sleep after learning has beneficial effects on the later retrieval of newly acquired memories. The neural mechanisms underlying these effects are becoming increasingly clear as well, particularly those of non-REM sleep. However, much is still unknown about the sleep and memory relationship: the sleep state or features of sleep physiology that associate with memory performance often vary by task or experimental design, and the nature of this variability is not entirely clear. This paper describes pertinent features of sleep physiology and provides a detailed review of the scientific literature indicating beneficial effects of post-learning sleep on memory retrieval. This paper additionally introduces a hypothesis which attributes these beneficial effects of post-learning sleep to separable processes of memory reinforcement and memory refinement whereby reinforcement supports one's ability to retrieve a given memory and refinement supports the precision of that memory retrieval in the context of competitive alternatives. It is observed that features of non-REM sleep are involved in a post-learning substantiation of memory representations that benefit memory performance; thus, memory reinforcement is primarily attributed to non-REM sleep. Memory refinement is primarily attributed to REM sleep given evidence of bidirectional synaptic plasticity in REM sleep and findings from studies of selective REM sleep deprivation

Memory for Political Messages: the Role of Inhibition and Prior Attitudes

Abstract Retrieval-induced forgetting (RIF) is a phenomenon wherein repeatedly accessing a portion of information causes decreases in memory for related information that is not practiced (Anderson, Bjork, Bjork, 1994). This study applied the retrieval practice paradigm commonly used in cognitive research to persuasive political statements in order to understand the cognitive implications that selective exposure to political messages may have. This study had a mixed design, with retrieval practice agreement (proattitudinal or counterattitudinal), attitude extremity (neutral, moderate, extreme), gender, and practiced issue (affirmative action or gun control) as between subject variables and item practice status (retrieval practiced, non-practiced/shared stance, non-practiced/shared issue, and non-practiced/different issue) as a within-subjects variable. As it was hypothesized that participants\u27 attitudes might moderate RIF effects, attitude strength and extremity for each issue were assessed as well as potential moderating variables. Participants (n=l24) were presented all sentences in the study phase, were given 3 trials of retrieval practice for 5 sentences from one stance, and then a recognition task determined participants\u27 accuracy and response time in distinguishing all original sentences from lures (inversions of those original sentences). Analysis (controlling for attitude strength and retrieval practice accuracy) failed to reveal any signs of RIF for hit or false alarm rates or in reaction times, but attitude extremity did affect recognition: while there was no difference between unpracticed items for neutral participants, moderate participants had lower hit rates for unpracticed control items relative to unpracticed items from the same issue as the practiced items. Males showed more false alarms for unpracticed/same stance items relative to all other items while females showed fewer false alarms for these items. While there was no clear evidence of RIF, this research may contribute to future studies on this topic

Effects of slow oscillatory transcranial direct current stimulation (so-tDCS) on sleep-dependent memory consolidation

Hintergrund: Es gibt zunehmende Evidenz, dass Schlaf eine aktive Rolle in der Gedächtniskonsolidierung spielt. Insbesondere wird in diesem Zusammenhang die Bedeutung langsamer Oszillationen (< 1 Hz) für die schlafbezogenen Gedächtniskonsolidierungsprozesse diskutiert. In einer wegweisenden Studie, in der eine langsam oszillierende transkranielle Gleichstromstimulation (so-tDCS) appliziert wurde, konnte bei jungen Probanden eine erfolgreiche exogene Manipulation dieser langsamen Oszillationen sowie eine Verbesserung des deklarativen Gedächtnisses beobachtet werden. Spätere Studien, die mit ähnlicher Methodik durchgeführt wurden, zeigten jedoch widersprüchliche Ergebnisse. Die Wirksamkeit dieser neuromodulatorischen Technik wird deshalb in Frage gestellt. Ziel: In dieser Studie wurde untersucht, ob mittels so-tDCS spezifische neurale Oszillationen während des Schlafes moduliert werden können und das deklarative Gedächtnis gesteigert werden kann. Das Ziel war es, die Ergebnisse der Pionierstudie an gesunden jungen Probanden zu replizieren. Dazu wurde ein leicht modifiziertes Stimulationsprotokoll verwendet, welches zuvor an älteren Probanden angewandt wurde. Methoden: In einem doppelblinden, placebo-kontrollierten Laborexperiment mit randomisiertem Crossover-Design wurde der Effekt von bifrontal applizierter anodaler so-tDCS (Frequenz 0,75 Hz) während des Schlafstadium 2 (N2) des Non-REM Schlafes auf die Ergebnisse eines Wortpaar-Assoziationstests und einer Finger-Tapping-Aufgabe an 23 gesunden Probanden (Mittelwert ± Standardabweichung: 23.2 ± 1.9 Jahre; 13 Frauen) überprüft. Stimulationseffekte wurden für Schlafstadien, die Schlafspindeldichte und die EEG-Power analysiert. Weiterhin wurde der Einfluss der so-tDCS auf die deklarative und prozedurale Gedächtniskonsolidierung überprüft. Ergebnisse: Weder auf Verhaltens-, noch auf physiologischer Ebene wurden signifikante Stimulationseffekte beobachtet. Unter beiden Stimulationsbedingungen verbesserte sich die Gedächtnisleistung über Nacht bei der prozeduralen Aufgabe, während sie sich bei der deklarativen Aufgabe verschlechterte. Hatten die Probanden jedoch zusätzliche Lernmöglichkeiten, verringerte dies die Abnahme der deklarativen Gedächtnisleistung. Unabhängig von der Stimulation kam es zu einer Abnahme der schnellen parietalen Spindeldichte von der Baseline (vor Stimulation) zu den stimulationsfreien Intervallen, während bei der langsamen frontalen Spindeldichte kein signifikanter Unterschied auftrat. Schlussfolgerungen: Die vorliegende Studie konnte die Ergebnisse der Pionierstudie nicht reproduzieren. Unsere Ergebnisse stimmen jedoch mit einer früheren Studie überein, die das gleiche Stimulationsprotokoll bei älteren Probanden verwendete. Das Ausmaß der nächtlichen Konsolidierung von deklarativen Gedächtnisinhalten war davon abhängig, ob es eine Möglichkeit zur Wiederholung der Lerninhalte gab. Die Standardisierung des Studienprotokolls und eine Berücksichtigung individueller Variabilität sind essentiell für so-tDCS Studien.Background: There is growing evidence that sleep plays an active role in memory consolidation. Specially, there are indications that slow oscillations (< 1 Hz) might be involved in sleep-dependent memory consolidation processes. Employing slow oscillatory transcranial direct current stimulation (so-tDCS) during slow-wave sleep, a pioneer study reported a successful exogenous manipulation of slow oscillations accompanied by an enhancement of declarative memory in young participants. However, subsequent studies using similar methodologies yielded contradictory results questioning the effectiveness of this neuromodulatory technique. Aim: This study attempted to modulate specific neural oscillations during sleep and boost declarative memory using so-tDCS with the aim to replicate the findings of a seminal study in young healthy adults, using a slightly modified stimulation protocol previously implemented in elderly participants. Methods: The effect of anodal so-tDCS applied bifrontally (frequency 0.75 Hz) during non-rapid eye movement (NREM) stage 2 sleep (N2) was assessed on a word-pair task and a sequential finger tapping task in 23 healthy participants (mean ± Sd: 23.2 ± 1.9 years; 13 women) in a double-blind, placebo controlled, counterbalanced, randomized crossover design. Stimulation effects were analyzed on sleep stages, sleep spindle densities, and EEG power, as well as on declarative and procedural memory performances. Results: No significant stimulation effects were observed neither on the behavioral performance nor at the physiological level. Under both stimulation conditions, overnight retention raised in the procedural task and declined in the declarative task. However, when participants had additional learning opportunities, the decline in declarative memory performance diminished. Regardless of stimulation, fast parietal spindle densities decreased from baseline (prior to stimulation) to stimulation-free intervals, while slow frontal spindle density showed no significant changes. Conclusion: The present study failed to replicate the results of the pioneer study in this field. However, our findings are in line with a previous study that used the same stimulation protocol in elderly participants. Overnight retention performances in declarative memory were dependent on re-encoding opportunities. Finally, it should be noted that protocol standardization and variability control are essential in so-tDCS studies

The contributions of sleep-related consolidation to emotional item and associative memory.

Extant empirical evidence of the past two decades suggests a pivotal role of sleep in system consolidation of episodic memory. Models of active system consolidation (Diekelmann & Born, 2010; Rasch & Born, 2013) propose that periods of restricted sensory processing that are pervasive during slow wave sleep (SWS) provide the opportunity of coordinated reactivations. These reactivations are assumed to result in subsequent redistribution of memory representations from intermediate maintenance in the hippocampus toward long-term storage in neocortical networks. However, newly emerging evidence (Genzel, Spoormaker, Konrad, & Dresler, 2015; Hutchison & Rathore, 2015) indicates that a consolidation process, which is highly distinct from the former framework, unfolds across periods of rapid eye movement (REM) sleep, fostering the selective enhancement of emotional memory retrieval. Critically, the interactions of both processes with regard to emotional associative memory have remained largely unexplored at present. This motivated the objectives of the present thesis, which aimed to generate a more comprehensive understanding of the differential contributions of consolidation processes during SWS and REM sleep to (non-)emotional item and associative memory retention. This was addressed in two consecutive experiments, which examined behavioral performance changes across different intervals of sleep, and aimed to link these to specific oscillatory features of SWS (sleep spindle activity) and REM sleep (right-frontal theta lateralization). In experiment 1 consolidation processes were studied in a split-night-design, which contrasts the effects of early night sleep (entailing high amounts of SWS) with those of late night sleep (which is predominated by REM sleep episodes). In order to dissociate item memory from distinct retrieval of contextual features, participants performed a source memory task that ascertained the accurate recognition of (non-)emotional images, as well as the accurate retrieval of the initial screen location (right or left) during encoding. Analyses revealed a significant consolidation benefit for emotional images with regard to item recognition, irrespective of sleep. Source memory performance was differentially modulated across early and late night sleep as a function of stimulus valence. While early night sleep was associated with a selective retention benefit for neutral source memory, late night sleep yielded a selective benefit to emotional source recognition across sleep. This dissociation was further substantiated on a neurophysiological level, by means of selective correlations between spindle power (SWS) and neutral memory performance in the early sleep group, which was complimented by a selective association between right-frontal theta laterality (REM sleep), and emotional source recognition in the late sleep group. As such, the results of experiment 1 genuinely revealed dissociable processes related to the consolidation of emotional and neutral source memory emerging across sleep. Moreover, this extends prior conceptions (Spoormaker, Czisch, & Holsboer, 2013) of consolidation processes during REM sleep, as these were believed to be confined to item memory reprocessing. Experiment 2 attempted to address the generalizability of these previous findings with regard to the critical timing and duration of these consolidation processes, as well as concerning the effects of perceptual integration processes at the encoding stage. In order to examine performance changes across a restricted sleep interval entailing high proportions of REM sleep, an early morning nap paradigm was employed in which participants were randomly allocated to a wakeful control condition or to a 120-minute nap sleep condition in the early morning hours. As previous effects with regard to REM sleep (experiment 1) may be bound to certain preconditions at encoding (Murray & Kensinger, 2012), specifically to the inherent level of perceptual integration between emotional items and source features, experiment 2 adopted a different approach requiring the active integration of both components at the encoding stage. To this end, item and associative recognition were probed by means of a paired-associates task, which required the accurate retrieval of arbitrary object-scene-associations (entailing emotional or neutral scenes) formed during the encoding phase. Analyses yielded a selective, sleep-related retention benefit in associative recognition for both stimulus categories. However, this benefit in performance was again partially dissociable on a neurophysiological level as evident by selective correlations between spindle density during non-rapid eye movement (NREM) sleep and neutral associative memory performance. These results reinforce the former findings of experiment 1, demonstrating that similar consolidation effects related to SWS and REM sleep can be retained on a behavioral level after a brief interval of sleep during the daytime and in a dissimilar task design, requiring active integration of item and context at encoding. However, the lack of a robust correlation with regard to right-frontal theta lateralization signifies that the circadian modulations and neurophysiological specifics of REM sleep, place certain restrictions on the accurate assessment of related processes in diurnal nap paradigms. In summary, the present thesis constitutes a first systematic approach towards dissociating the contributions of REM sleep and SWS to emotional associative memory consolidation, across two consecutive but dissimilar study designs. The yielded findings originally suggest that consolidation processes during both sleep stages are dissociable, but beyond this, contribute independently to memory retention of emotional and neutral associations. This was also substantiated on a neurophysiological level with regard to selective correlations between oscillatory features of both sleep stages and memory performance. Moreover, in support of previous conceptions (Hutchison & Rathore, 2015), it was genuinely established that REM sleep exhibits the unique capacity to influence associative memory of emotional stimuli. The exact mechanism by which this is accomplished remains to be elucidated in future experiments.Eine Vielzahl empirischer Befunde der letzten zwei Jahrzehnte belegen, dass der Schlaf eine tiefgreifende Rolle in der Gedächtniskonsolidierung zwischen unterschiedlichen Gedächtnissystems einnimmt. Sukzessive verfeinerte Modelle über aktive Vorgänge der „Systemkonsolidierung“ (Diekelmann & Born, 2010; Rasch & Born, 2013) legen nahe, dass Phasen eingeschränkter sensorischer Verarbeitung, die über den Tiefschlaf hinweg dominieren, ein Zeitfenster bieten in dem Gedächtnisspuren im Hippocampus in koordinierter Weise reaktiviert werden können. Diese Reaktivierungen gehen mit einer Integration der jeweiligen Gedächtnisinhalte in neokortikalen Netzwerken einher, die eine langfristige Aufrechterhaltung des Gedächtnisabrufs ermöglichen. Neue Befunde (Genzel et al., 2015; Hutchison & Rathore, 2015) legen allerdings nahe, dass sich ein weiterer Konsolidierungsprozess über den Schlaf hinweg vollzieht, der zu einer selektiven Aufrechterhaltung emotionaler Gedächtnisinhalte beiträgt. Dieser Prozess ist wiederum assoziiert mit dem Auftreten von REM-Schlaf (REM, engl. Rapid Eye Movement) Episoden. Bislang ist jedoch unklar, wie beide Konsolidierungsprozesse über unterschiedliche Schlafstadien hinweg miteinander interagieren in Bezug auf das emotionale Assoziationsgedächtnis. Dies bildete den Ausgangspunkt der vorliegenden Arbeit, die ein umfassenderes Verständnis hinsichtlich der Beiträge unterschiedlicher Konsolidierungsprozesse im Tiefschlaf und REM Schlaf in der Aufrechterhaltung des (nicht-)emotionalen Item- und Assoziationsgedächtnisses anstrebt. Dies wurde in zwei aufeinander aufbauenden Experimenten näher beleuchtet, in denen behaviorale Leistungsveränderungen über unterschiedliche Schlafintervalle untersucht wurden mit dem Ziel diese mit spezifischen oszillatorischen Merkmalen des Tiefschlafs (Schlafspindel Aktivität) und des REM Schlafs (Rechts-frontale Theta Lateralisierung) in Verbindung zu bringen. In Experiment 1 wurden diese Konsolidierungsprozesse in einem „Split-night-design“ untersucht, das die Möglichkeit bietet, frühen Nachtschlaf (mit hoher Tiefschlafdauer) mit spätem Nachtschlaf (der von REM-Schlaf Episoden dominiert wird) zu kontrastieren. Um das Itemgedächtnis von dem distinkten Abruf kontextueller Merkmale dissoziieren zu können, wurde eine Quellengedächtnisaufgabe von den Probanden bearbeitet, in der sowohl das Wiedererkennen (nicht)emotionaler Bilder als auch der Abruf der initialen Bildschirmposition (rechts oder links) in der Lernphase erfasst wurde. Die berichteten Analysen weisen auf einen signifikanten Konsolidierungsvorteil für das Wiedererkennen emotionaler Bilder über die Zeit hinweg hin, der jedoch unabhängig vom Schlaf auftritt. Die Quellengedächtnisleistung wird hingegen differentiell über den frühen und späten Nachtschlaf in Abhängigkeit von der Stimulusvalenz aufrechterhalten. Während früher Nachtschlaf mit einer selektiven Aufrechterhaltung des neutralen Quellengedächtnisses assoziiert war, konnte der späte Nachtschlaf mit einer selektiven Erhaltung des emotionalen Quellengedächtnisses in Verbindung gebracht werden. Diese Dissoziation war darüber hinaus auf neurophysiologischer Ebene nachweisbar anhand selektiver Korrelationen zwischen der Spindelaktivität im Tiefschlaf und der neutralen Gedächtnisleistung über den frühen Nachtschlaf und einer selektiven Korrelation zwischen der rechts-frontalen Theta Lateralisierung im REM Schlaf und der emotionalen Quellengedächtnisleistung über den späten Nachtschlaf. Die Ergebnisse des ersten Experiments eröffnen eine neue Perspektive, indem sie die Existenz zweier dissoziierbarer Prozesse in der Konsolidierung des emotionalen und neutralen Quellengedächtnisses über den Schlaf hinweg nahelegen. Im Zuge dessen erweitern die vorliegenden Ergebnisse vorangegangene Konzepte (Spoormaker et al., 2013) der Gedächtniskonsolidierung im REM Schlaf, die bislang eine eingeschränkte Wirkung auf das Itemgedächtnis prädizierten. Das Ziel von Experiment 2 war es, diese neuen Ergebnisse auf ihre Generalisierbarkeit hin zu prüfen, insbesondere hinsichtlich der kritischen Zeitverlaufs und der Dauer der zugrundliegenden Konsolidierungsprozesse und in Bezug auf die Bedeutung perzeptueller Integrationsprozesse während der Enkodierphase. Um Veränderungen in der Gedächtnisleistung über ein kurzes Schlafintervall mit hohen REM-Schlaf-Anteilen zu untersuchen wurde ein Kurzschlaf Paradigma am frühen Morgen eingesetzt in dem Probanden einer Wachkontrollbedingung oder einer 120-minütigen Tagschlafbedingung am frühen Morgen zugewiesen wurden. Die vorangegangenen Ergebnisse aus Experiment 1 hinsichtlich der Effekte des REM-Schlafs könnten unter Zugrundelegung der Literatur (Murray & Kensinger, 2013) an bestimmte Bedingungen während er Enkodierungsphase gekoppelt sein, speziell an den inhärente Grad der perzeptuellen Integration zwischen emotionalen Items und ihren Quellenmerkmalen. Um dies zu prüfen wurde in Experiment 2 eine andere Herangehensweise mit einer Gedächtnisaufgabe, die eine aktive Integration beider Komponenten während der Enkodierung erforderlich machte, gewählt. Item- und Assoziationsgedächtnis wurden über das Behalten paarweise gelernter Assoziationen zwischen (nicht)emotionalen Bildern und Alltagsobjekten erfasst. Die korrespondierenden Analysen erbrachten einen selektiven, schlafbezogenen Vorteil in der Aufrechterhaltung der assoziativen Gedächtnisleistung über die Zeit hinweg in beiden Stimuluskategorien. Darüber hinaus war dieser Effekt erneut teilweise dissoziierbar auf neurophysiologischer Ebene, was sich in selektiven Korrelationen der Spindeldichte während des non-rapid eye movement (NREM) Schlafs zu der neutralen Assoziationsgedächtnisleistung wiederspiegelte. Diese Ergebnisse untermauern die vorangegangen Befunde aus Experiment 2, indem ähnliche Konsolidierungseffekte des Tiefschlafs und des REM Schlafs über ein kurzes Schlafintervall am frühen Morgen und innerhalb eines Aufgaben-Paradigmas, dass die aktive Integration während der Enkodierungsphase erforderte, auf behavioraler Ebene bestätigt werden konnten. Dennoch verweist das Ausbleiben einer robusten Korrelation zu der rechts-frontalen Theta Lateralisierung im REM-Schlaf darauf, dass zirkadiane Modulationen und neurophysiologische Besonderheiten des REM-Schlafs gewisse Begrenzungen in der akkuraten Erfassung dieser Prozesse innerhalb von Kurzschlaf-Paradigmen während des Tages setzen. Die vorliegende Arbeit stellt eine erste systematische Annäherung an eine Dissoziierung der Beiträge des Tiefschlafs und des REM-Schlafs in der Konsolidierung des emotionalen Assoziationsgedächtnisses dar, die über zwei aufeinander aufbauende aber unterschiedliche Studiendesigns hinweg angestrebt wurde. Die daraus hervorgegangenen Ergebnisse legen erstmals nahe, dass Konsolidierungsprozesse über beide Schlafstadien dissoziierbar sind aber darüber hinaus gehend eigenständig zu einer Aufrechterhaltung der Gedächtnisleistung für neutrale und emotionale Assoziationen beitragen. Dies konnte auch auf neurophysiologischer Ebene über selektive Korrelationen zu oszillatorischen Merkmalen beider Schlafstadien substantiiert werden. Darüber hinaus konnte erstmalig nachgewiesen werden, dass Prozesse während des REM Schlaf über die Kapazität verfügen auf das assoziative Erinnern emotionaler Inhalte einzuwirken in Übereinstimmung zu neueren theoretischen Konzepten (Hutchison & Rathore, 2015). Der genaue Mechanismus über den dies bewirkt wird muss in zukünftigen Experimenten näher beleuchtet werden

The Psychology of Intelligence Analysis: Drivers of Prediction Accuracy in World Politics

This article extends psychological methods and concepts into a domain that is as profoundly consequential as it is poorly understood: intelligence analysis. We report findings from a geopolitical forecasting tournament that assessed the accuracy of more than 150,000 forecasts of 743 participants on 199 events occurring over 2 years. Participants were above average in intelligence and political knowledge relative to the general population. Individual differences in performance emerged, and forecasting skills were surprisingly consistent over time. Key predictors were (a) dispositional variables of cognitive ability, political knowledge, and open-mindedness; (b) situational variables of training in probabilistic reasoning and participation in collaborative teams that shared information and discussed rationales (Mellers, Ungar, et al., 2014); and (c) behavioral variables of deliberation time and frequency of belief updating. We developed a profile of the best forecasters; they were better at inductive reasoning, pattern detection, cognitive flexibility, and open-mindedness. They had greater understanding of geopolitics, training in probabilistic reasoning, and opportunities to succeed in cognitively enriched team environments. Last but not least, they viewed forecasting as a skill that required deliberate practice, sustained effort, and constant monitoring of current affairs

Prior knowledge contribution to declarative learning. A study in amnesia, aging and Alzheimer's disease

L'étude expérimentale de la mémoire humaine a connu deux moments historiques dans les soixante dernières années. 1957 marque la découverte du rôle du lobe temporal interne bilatéral dans l'apprentissage conscient, déclaratif. 1997 marque la découverte de deux systèmes de mémoire déclarative, épisodique et sémantique. Ces découvertes résultent d'études de cas en neuropsychologie. Cette thèse s'inscrit dans la tradition neuropsychologique: sa genèse doit tout à un patient souffrant d'une forme atypique d'amnésie développementale, le patient KA. Son point de départ est une étude de cas approfondie, avec deux résultats surprenants. Malgré une amnésie sévère, KA dispose de connaissances sémantiques exceptionnelles. Par ailleurs, il montre des capacités préservées d'apprentissage explicite, mais uniquement pour des stimuli concrets, pas abstraits. En conséquence, cette thèse a exploré deux pistes de recherche. Premièrement, nous avons caractérisé les processus préservés d'apprentissage déclaratif et l'anatomie cérébrale chez ce patient. Deuxièmement, nous avons étudié le rôle des connaissances préalables dans l'apprentissage: comment ce que l'on sait influence ce dont nous nous souvenons ? Une première série d'expériences montre chez ce patient une atteinte sévère et sélective de l'ensemble du système hippocampique, alors que les structures sous- hippocampiques (cortex entorhinal, périrhinal et parahippocampique) sont préservées. Malgré une amnésie épisodique sévère, nous montrons des connaissances sémantiques supranormales et des aptitudes d'apprentissage explicite rapide. Ces aptitudes sont toutefois restreintes aux stimuli associés à des connaissances préalables. Une seconde série d'expériences explore l'hypothèse selon laquelle les connaissances préalables facilitent l'apprentissage en mémoire déclarative, même dans les situations où le lobe temporal interne est fragilisé, comme dans le vieillissement, ou lésé, comme chez le patient KA ou dans la maladie d'Alzheimer. Nos résultats suggèrent l'existence de processus d'apprentissage rapide en mémoire déclarative, indépendants du système hippocampique et sensibles à la présence de représentations préexistantes. Ces processus semblent affectés par la maladie d'Alzheimer, et ce en lien avec un défaut d'activité des régions sous-hippocampiques antérieures. A l'inverse, les sujets âgés sains peuvent utiliser les connaissances préalables et pourraient ainsi compenser le déclin de la mémoire associative. Ce travail s'accorde avec les modèles postulant une dissociation fonctionnelle au sein du lobe temporal interne pour l'apprentissage déclaratif. Il soutient les propositions neurocognitives et computationnelles récentes, suggérant une voie d'apprentissage néocortical rapide mobilisable dans certaines circonstances. Il met en exergue la dynamique des apprentissages en mémoire déclarative et notamment l'intrication fondamentale entre "savoir" et "se souvenir". Ce que je sais a un impact profond sur ce dont je vais me souvenir. Cette thèse permet d'envisager de nouveaux outils cognitifs pour le diagnostic de la maladie d'Alzheimer. De plus, il semble que des lésions temporales internes auront un impact distinct sur l'apprentissage selon le statut des informations à mémoriser en mémoire à long terme, offrant un regard nouveau sur les effets stimulus-dépendants dans l'amnésie. Une considération approfondie des connaissances préalables associées au contenu de nos expériences, et leur caractérisation détaillée, est requise pour affiner les modèles de la mémoire déclarative. Ces résultats apportent de nouvelles pistes de recherche quant aux circonstances épargnant l'apprentissage, notamment associatif, lors du vieillissement. Plus généralement, ils contribuent à la compréhension des déterminants d'un apprentissage réussi, en mettant l'accent sur les recouvrements entre processus de récupération et d'acquisition. Des applications potentielles en découlent dans le domaine éducatif.The experimental study of human memory has had two historic moments in the last sixty years. 1957 marks the discovery of the role of the medial temporal lobes in conscious learning. 1997 marks the discovery of two systems of declarative memory, namely episodic and semantic memories. These major breakthroughs are owed to clinical case studies in neuropsychology. This thesis follows on from the neuropsychological tradition: its genesis owes everything to a patient suffering from an atypical form of developmental amnesia, the patient KA. The starting point of this work was a thorough neuropsychological study of this patient. Two striking findings shortly arose. First, despite lifelong amnesia, KA had acquired exceptional levels of knowledge about the world. Second, remaining explicit learning abilities were restricted to meaningful, not meaningless, memoranda. As a consequence, we have investigated two research pathways in that thesis. First, we aimed at better characterizing preserved learning abilities and brain structure of the patient KA. Second, our goal was to explore how prior knowledge affects new declarative learning or, put simply, how do we learn what we know? In a first series of behavioural and neuroimaging experiments, we have shown in this patient a severe and selective damage of the whole extended hippocampal system, but preserved subhippocampal structures (entorhinal, perirhinal and parahippocampal cortex). The patient suffers from severe episodic amnesia, but we bring striking evidence for supranormal semantic knowledge as well as normal explicit learning skills. These skills were, however, restricted to familiar stimuli, that is, stimuli carrying pre-experimental knowledge. In a second series of behavioural and neuroimaging experiments, we explored the hypothesis that prior knowledge can facilitate new learning in declarative memory, even in aging or in situations where structures of the medial temporal lobe are or injured, as in amnesia or Alzheimer's disease. Our results suggest the existence of processes allowing fast learning in declarative memory, independently of the hippocampal system, and that are sensitive to the presence of pre-existing representations in long-term memory. Such learning processes appear to be selectively affected by Alzheimer's disease at the pre-dementia stage, in relation to a lack of activation of subhippocampal regions. In contrast, healthy elderly were able to rely on these learning processes to compensate for the decline in associative memory associated with aging. This work lends support to the models postulating a functional dissociation with respect to learning in declarative memory. It indeed strengthens recent neurocognitive and computational accounts that suggest a rapid neocortical learning path under certain circumstances. It highlights the dynamics of learning in declarative memory and in particular the fundamental entanglement between "knowing" and "remembering". What I know profoundly impacts what I will remember. The present thesis points towards new cognitive tools for the diagnosis of Alzheimer's disease. It further brings evidence that medial temporal lesions differentially impact learning depending on the status of the memoranda in long-term memory, which sheds a new light on material-specific effects in amnesia. Our work speaks for a thorough consideration of whether the contents of events have prior representations within long-term memory, and to further better characterize their nature if we are to better understand learning mechanisms. It also brings additional clues for a deeper understanding of how learning and memory can be preserved in aging. More generally, it contributes to a better understanding of the factors determining successful learning, with a focus on how retrieval and acquisition processes overlap during learning. Such findings have potential applications in the educational field

Memory capacity in the hippocampus

Neural assemblies in hippocampus encode positions. During rest, the hippocam- pus replays sequences of neural activity seen during awake behavior. This replay is linked to memory consolidation and mental exploration of the environment. Re- current networks can be used to model the replay of sequential activity. Multiple sequences can be stored in the synaptic connections. To achieve a high mem- ory capacity, recurrent networks require a pattern separation mechanism. Such a mechanism is global remapping, observed in place cell populations. A place cell fires at a particular position of an environment and is silent elsewhere. Multiple place cells usually cover an environment with their firing fields. Small changes in the environment or context of a behavioral task can cause global remapping, i.e. profound changes in place cell firing fields. Global remapping causes some cells to cease firing, other silent cells to gain a place field, and other place cells to move their firing field and change their peak firing rate. The effect is strong enough to make global remapping a viable pattern separation mechanism. We model two mechanisms that improve the memory capacity of recurrent net- works. The effect of inhibition on replay in a recurrent network is modeled using binary neurons and binary synapses. A mean field approximation is used to de- termine the optimal parameters for the inhibitory neuron population. Numerical simulations of the full model were carried out to verify the predictions of the mean field model. A second model analyzes a hypothesized global remapping mecha- nism, in which grid cell firing is used as feed forward input to place cells. Grid cells have multiple firing fields in the same environment, arranged in a hexagonal grid. Grid cells can be used in a model as feed forward inputs to place cells to produce place fields. In these grid-to-place cell models, shifts in the grid cell firing patterns cause remapping in the place cell population. We analyze the capacity of such a system to create sets of separated patterns, i.e. how many different spatial codes can be generated. The limiting factor are the synapses connecting grid cells to place cells. To assess their capacity, we produce different place codes in place and grid cell populations, by shuffling place field positions and shifting grid fields of grid cells. Then we use Hebbian learning to increase the synaptic weights be- tween grid and place cells for each set of grid and place code. The capacity limit is reached when synaptic interference makes it impossible to produce a place code with sufficient spatial acuity from grid cell firing. Additionally, it is desired to also maintain the place fields compact, or sparse if seen from a coding standpoint. Of course, as more environments are stored, the sparseness is lost. Interestingly, place cells lose the sparseness of their firing fields much earlier than their spatial acuity. For the sequence replay model we are able to increase capacity in a simulated recurrent network by including an inhibitory population. We show that even in this more complicated case, capacity is improved. We observe oscillations in the average activity of both excitatory and inhibitory neuron populations. The oscillations get stronger at the capacity limit. In addition, at the capacity limit, rather than observing a sudden failure of replay, we find sequences are replayed transiently for a couple of time steps before failing. Analyzing the remapping model, we find that, as we store more spatial codes in the synapses, first the sparseness of place fields is lost. Only later do we observe a decay in spatial acuity of the code. We found two ways to maintain sparse place fields while achieving a high capacity: inhibition between place cells, and partitioning the place cell population so that learning affects only a small fraction of them in each environment. We present scaling predictions that suggest that hundreds of thousands of spatial codes can be produced by this pattern separation mechanism. The effect inhibition has on the replay model is two-fold. Capacity is increased, and the graceful transition from full replay to failure allows for higher capacities when using short sequences. Additional mechanisms not explored in this model could be at work to concatenate these short sequences, or could perform more complex operations on them. The interplay of excitatory and inhibitory populations gives rise to oscillations, which are strongest at the capacity limit. The oscillation draws a picture of how a memory mechanism can cause hippocampal oscillations as observed in experiments. In the remapping model we showed that sparseness of place cell firing is constraining the capacity of this pattern separation mechanism. Grid codes outperform place codes regarding spatial acuity, as shown in Mathis et al. (2012). Our model shows that the grid-to-place transformation is not harnessing the full spatial information from the grid code in order to maintain sparse place fields. This suggests that the two codes are independent, and communication between the areas might be mostly for synchronization. High spatial acuity seems to be a specialization of the grid code, while the place code is more suitable for memory tasks. In a detailed model of hippocampal replay we show that feedback inhibition can increase the number of sequences that can be replayed. The effect of inhibition on capacity is determined using a meanfield model, and the results are verified with numerical simulations of the full network. Transient replay is found at the capacity limit, accompanied by oscillations that resemble sharp wave ripples in hippocampus. In a second model Hippocampal replay of neuronal activity is linked to memory consolidation and mental exploration. Furthermore, replay is a potential neural correlate of episodic memory. To model hippocampal sequence replay, recurrent neural networks are used. Memory capacity of such networks is of great interest to determine their biological feasibility. And additionally, any mechanism that improves capacity has explanatory power. We investigate two such mechanisms. The first mechanism to improve capacity is global, unspecific feedback inhibition for the recurrent network. In a simplified meanfield model we show that capacity is indeed improved. The second mechanism that increases memory capacity is pattern separation. In the spatial context of hippocampal place cell firing, global remapping is one way to achieve pattern separation. Changes in the environment or context of a task cause global remapping. During global remapping, place cell firing changes in unpredictable ways: cells shift their place fields, or fully cease firing, and formerly silent cells acquire place fields. Global remapping can be triggered by subtle changes in grid cells that give feed-forward inputs to hippocampal place cells. We investigate the capacity of the underlying synaptic connections, defined as the number of different environments that can be represented at a given spatial acuity. We find two essential conditions to achieve a high capacity and sparse place fields: inhibition between place cells, and partitioning the place cell population so that learning affects only a small fraction of them in each environments. We also find that sparsity of place fields is the constraining factor of the model rather than spatial acuity. Since the hippocampal place code is sparse, we conclude that the hippocampus does not fully harness the spatial information available in the grid code. The two codes of space might thus serve different purposes

Acute Exercise and Creativity: Embodied Cognition Approaches

This dissertation manuscript is the culmination of three years of research examining several unique, exercise-induced mechanisms underlying creativity. This collection of work addresses historical and current empirical concepts of creativity in a narrative review, providing recommendations for future research. Several reviews follow this introduction, highlighting the proposed effects of exercise on creativity, putative mechanisms for creativity, and the effects of exercise and embodied manipulations on creative behavior. Multiple experiments utilizing moderate-intensity exercise as a theoretical stimulus for higher-order cognitions were conducted to investigate associations between exercise and creativity, which lead to the final dissertation experiment. The dissertation experiment was the first to provide statistically significant evidence for acute, moderate-intensity treadmill exercise coupled with anagram problem-solving to prime subsequent RAT completion compared to a non-exercise, priming only condition. We emphasize that the additive effects of exercise plus priming may be a viable strategy for enhancing verbal convergent creativity. Future research is warranted to explore a variety of priming effects on the relationship between exercise, embodied interventions, and creativityThis dissertation manuscript is the culmination of three years of research examining several unique, exercise-induced mechanisms underlying creativity. This collection of work addresses historical and current empirical concepts of creativity in a narrative review, providing recommendations for future research. Several reviews follow this introduction, highlighting the proposed effects of exercise on creativity, putative mechanisms for creativity, and the effects of exercise and embodied manipulations on creative behavior. Multiple experiments utilizing moderate-intensity exercise as a theoretical stimulus for higher-order cognitions were conducted to investigate associations between exercise and creativity, which lead to the final dissertation experiment. The dissertation experiment was the first to provide statistically significant evidence for acute, moderate-intensity treadmill exercise coupled with anagram problem-solving to prime subsequent RAT completion compared to a non-exercise, priming only condition. We emphasize that the additive effects of exercise plus priming may be a viable strategy for enhancing verbal convergent creativity. Future research is warranted to explore a variety of priming effects on the relationship between exercise, embodied interventions, and creativit