Дисертації з теми "Neutral emotion"

Selective attention has been studied extensively and it is shown, for example, that individuals with conditions such as anxiety show attention bias to threat-related stimuli. It has been proposed that humans are predisposed or that it is naturally adaptive to selectively attend to emotional stimuli (Lang, 2000). Similarly, LeDoux (1996) and others have proposed limbic brain networks allowing for quick and automatic, but sometimes inaccurate, processing of emotion which bypasses primary cortical areas. Along these lines, automatic attention bias to subliminal image cues in an adapted Posner Covert Attention Task was examined in the current study. A sample of 64 participants was used in each of three separate experiments to examine how individuals were cued subliminally by negative or positive emotional vs. neutral images and the modulation of covert attention by emotion. Due to automatic or motivated attention to emotionally salient stimuli, participants were expected to be facilitated in task performance by negative and positive emotional image cues, relative to neutral cues. Further, state anxiety and depression were expected to impact performance on emotional cueing as well. As expected in Experiment 1, subliminal images produced significant covert attentional cueing and only negative image cues compared to neutral ones produced response time (RT) reduction by valid cueing across both cue-target delay conditions. Further, cueing differences between neutral and negative images were seen only at short delays, supporting differential subliminal processing of emotional cues in attentional paradigms and supporting previous evidence of unconscious fear processing and specialized automatic fear networks. Moreover, in Experiment 2, when delays following subliminal cues were extended further, emotional cues did not differentially modulate covert attention, suggesting that subliminal emotional cueing seems to occur more immediately. Positive subliminal imagery in Experiment 3 was largely unsuccessful in differentially modulating covert attention compared to neutral cues, suggesting that positive information is either not effective in modulating covert attention or occurs over similar immediate time durations as negative cues in Experiment 1. Finally, the presence of self-reported state anxiety and depression affected task performance, especially in Experiment 1 negative for subliminal discrimination of negative vs. neutral image cues. Overall, the current study adds to the research literature which demonstrates that emotional information, especially negative imagery processed at short intervals, can be processed below awareness to modulate attention in a different manner than less salient neutral stimuli and this modulation is further influenced by state anxiety or depressive symptomatology. Implications of these findings and future directions for research are discussed.

Depression is a highly prevalent clinical condition which has been estimated to affect a growing part of the population in western countries. Alongside expenditure on diagnostics and treatment, there is a high economic impact due to lost productivity. Although a range of treatments are available, diagnoses are currently costly and require subjective assessment by a specialist. Moreover, treatment selection can be lengthy and can involve trial and error. To develop better diagnostics, stratification, and treatments for depression, we need a better understanding of the condition across different levels - from neural mechanisms to cognition and behaviour. Computational modelling is an emergent theory-driven approach which can aid linking data across different levels of analysis - from neural mechanisms and computations in the brain, to cognitive algorithms and observable behaviour. Some models integrate diverse findings and make predictions, while others enable inference of clinical measures which are not obvious in raw data. Modelling can lead to better understanding of depression, and in turn to better stratification and treatments. On the other hand, machine learning and classification methods can help detect clinically-relevant patterns in experimental data in a purely data-driven manner. This can lead to development of better screening and diagnostic methods. In the current work, we first review some of the most prominent neurocognitive theories of depression, as well as existing studies which used computational modelling methods. Based on our review, we argue that modelling can provide a rich set of tools for a better understanding of the condition. We then develop two novel computational modelling accounts of depression. In the first account, we propose an explicit mechanistic link between a robust behavioural negative bias effect and some of the widely reported or theorised neural aspects of depression - hyperactive amygdala and inhibited dopamine release. In the second account, we attempt to better explain depressive cognitive deficits and show how they can arise from depression-relevant etiological factors - altered valuation and controllability estimates. Finally, in the third part of this work we attempt to develop a novel system for detecting depressive symptoms based on a combination of face-tracking, eye-tracking and cognitive performance measures. We evaluate the system in a pilot experiment and show that a combination of measures can achieve better results than measures from each domain separately.

This paper describes two experiments, each of which investigated the impact of stress on human episodic memory. All participants watched narrated slide shows containing emotional and neutral information. Experiment 1 demonstrated that pre-learning exposure to a psychological stressor (the Trier Social Stress Test or "TSST"; Kirschbaum, Pirke & Hellhammer, 1993) preserved or enhanced memory for emotional aspects of the slide show, but impaired memory for neutral aspects of the slide show. Moreover, stress exposure disrupted memory for information that was visually and thematically central to the slide show. Memory for peripheral information, on the other hand, was unaffected by stress. Experiment 2 replicated these results and extended them to a similar paradigm, where participants viewed separate emotional and neutral slide shows, and saliva was tested for the stress hormones cortisol and norepinephrine. Similar to the results of Experiment 1, stress disrupted memory for the neutral slide show, but enhanced memory for the emotional slide show. Salivary cortisol levels at retrieval were negatively correlated with memory for the neutral slide show. These results are consistent with theories invoking differential effects of stress on brain systems responsible for encoding and retrieving emotional memories (the amygdala) and non-emotional memories (e.g. the hippocampal formation, frontal cortex), and inconsistent with the view that memories formed under high levels of stress are qualitatively the same as those formed under ordinary emotional circumstances. These data, which are also consistent with results obtained in a number of studies using animals and humans, have implications for the traumatic memory debate and theories regarding human memory.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2003.
Includes bibliographical references.
The cognitive and neural processes underlying memory formation may differ depending on the vividness, or detail, of information encoded. In Chapter 1, a divided attention paradigm was used to examine memory formation when resources are (a) devoted primarily to encoding and (b) directed away from encoding, and toward a secondary task. In condition (b) the memories formed often lacked vividness. The formation of these less detailed memories recruited right inferior prefrontal cortex (PFC) and left parahippocampal gyrus. The left inferior PFC and left anterior hippocampus were additionally recruited in condition (a) when vivid memories could be formed. Investigations of memories' vividness have typically included only neutral information. The studies in Chapter 2 revealed that emotional information is vividly remembered more frequently than information lacking emotional import. This enhancement occurred for words with valence only (i.e., negative words that did not elicit physiological arousal) as well as for arousing ("taboo") words, but was stronger for the arousing words. In Chapter 3 a divided attention paradigm was employed to investigate the contributions of automatic and controlled processing to the recollective enhancement for the emotional words. Automatic processes (unaffected by task manipulation) drove the enhancement for arousing words, whereas controlled processes (disrupted by task manipulation) supported the enhancement for words with valence only. Thus, dissociable cognitive processes contributed to the enhancement for the two types of emotional words. In Chapter 4, fMRI was used to examine whether distinct encoding processes underlie enhanced memory for words with valence only versus words with arousal.
(cont.) Successful encoding of words with valence only was via a PFC-hippocampal network associated with controlled encoding processes (e.g., elaboration and rehearsal), whereas successful encoding of arousing words was mediated by an amygdalar-hippocampal network that may be important for automatic processing of emotional content. In conclusion, distinct neural processes appear to support the ability to form vivid memories as compared to less detailed ones. The specific cognitive and neural processes depended on the emotional nature of the stimuli. Vividly-remembered neutral words, and words with valence only, relied on similar encoding processes. In contrast, dissociable processes mediated successful encoding of vividly-remembered arousing words.
by Elizabeth A. Kensinger.
Ph.D.

When consolidated memories are reactivated, they become labile and have to go through reconsolidation to become stabilized.  This property of memory may potentially be used to reduce the impact of highly negative episodic memories.  Because detailed and vivid negative episodic memories are mediated by high arousal, if arousal is lessened during reconsolidation, then memory accuracy and vividness should diminish.  In this study, I examine this hypothesis.  Participants viewed a stressful, suspenseful movie on Day 1 to develop negative episodic memories.  Then, 24 to 29 hours later, they saw a brief reminder of the stressful movie (or not), and then viewed a neutral (or positive) movie.  Another 24 to 29 hours later, I tested the accuracy, vividness, and anxiety associated with their memory of the stressful movie. Participants who watched the reminder and then the neutral movie showed reduced memory accuracy.  Despite the reduction in memory accuracy, their memory vividness and anxiety associated with the stressful movie did not decrease. The results partly supported my hypothesis.

Syftet med föreliggande studie är att undersöka hur olika typer av känslomässig

priming påverkar bedömningen av neutrala ansikten. I studien undersöks också hur

personlighetsegenskapen neuroticism påverkar denna bedömning, både enskilt och i

kombination med känslomässig priming. 82 försökspersoner deltog i undersökningen.

Primingen sker i form av emotionella ord som är positiva, negativ eller neutrala.

Tidigare studier har visat att neuroticism favoriserar negativa affekter, och hypotesen

i studien var att den negativa primingen ska ha större effekt på individer som ligger

högt på skalan som mäter neuroticism än på de som ligger lågt på skalan. Resultaten

av denna studie visade inga signifikanta huvudeffekter av vare sig priming eller

neuroticism, även signifikanta interaktionseffekt mellan dessa faktorer uteblev. En

förklaring till uteblivna resultat kan vara att neuroticism grupperna inte skilde sig

markant från varandra på just denna variabel och därför inte heller uppvisade några

skillnader i bedömningen av ansikten. En möjlig orsak till uteblivna primingeffekter

kan vara att bedömningsstimulit (ansiktena) visades under så lång tid att

försökspersonerna hann göra en medveten bearbetning av dessa.

碩士
國立中興大學
財務金融學系所
107
My research topic is " The relation between the moment of the Risk Neutral density and investor''s emotion under the dangerous period : Evidence from S&P stock option. In this paper we study information of the Risk Neutral density (RND) implied by the option price. Our research data use the American monthly stock option-S&P during the period from June 1,2000 until December 31,2017 (total of 212 months). We want to use the data to explain the relationship between the moment (standard deviation, Skewness ,and Kurtosis) and emotion of the investors. At the beginnings, we find that the density of the probability would be negative. It is irrational, so we should deal the data. And we found that the strike price''s delta were negative and the curve which was plotted with the strike price and delta didn''t smooth at all. When we deal this trouble, we would find when we solve this questions as soon as possible. Our research used the Consumer confidence index (CCI) and put call ratio as research''s index of emotion. And add the rational variable to understand whether irrational emotion would effect the investors or consumer''s directions. Besides we want to know at the dangerous period the RND''s moment would change by the investor''s direction or not . So our research has three focus: 1.The relation between the investor''s emotion and the RND moment. 2.When we add the rational variable would change the direction or not? 3. At the dangerous period, the result of 1 would change or not.

Human beings constantly deal with an enormous amount of information that cannot be processed at once. Given the limited cognitive resources available for the processing of incoming information, visual selective attention has the role to differentiate between competing stimuli in order to facilitate the processing of stimuli that are relevant for adaptive behaviours. From an evolutionary perspective, stimuli with emotional content, in particular those signalling danger or threat, are very powerful in attracting and holding attention even if they are task-irrelevant. Moreover, emotional stimuli get higher processing priority compared with other competing stimuli and their access to further processing and conscious perception is thought to be automatic, at least when sufficient cognitive resources are available. Therefore, avoiding emotional stimuli, especially those with negative content, requires a conspicuous amount of resources that, if engaged for a prolonged period of time in a highly demanding cognitive task, they can undergo depletion, and eventually lead to the mental fatigue phenomenon. We propose that the amount of resources specifically dedicated to selective attention are also limited, and that they can be depleted specifically, and possibly independently, from the resources available for other cognitive mechanisms. This work was planned in order to directly explore this possibility, assuming that the crucial resources necessary to overcome the impact of irrelevant emotional distractors are also involved in attentional processing, and – more specifically – in the filtering of distracting visual information. We expected that by heavily engaging these inhibitory mechanisms, providing conditions of heavy and persistent distraction, we would observe phenomena suggesting that they were being depleted during the course of the experimental session (i.e. one-hour session). In a series of visual search experiments, young adult participants had to discriminate a target stimulus, while ignoring a task-irrelevant distractor that could be present in a portion of trials. According to the aim of our research, in order to increase, on the one hand, the attentional load and, on the other, the need to filter out distracting information, task-irrelevant stimuli with emotional content were introduced prior to each visual search trial. I then measured performance to evaluate the overall impact of emotional stimuli, revealing that while the onset of all emotional stimuli affected attentional deployment in the subsequent trial, such impact was different according to the valence of the stimuli involved. Analysing the efficiency of distractor filtering processes over the experimental session, I observed changes in performance suggesting that the attentional resources specifically involved during the inhibition of distractors in the visual search task could indeed be depleted. By this new approach, in this series of studies I offered new evidence relative to the depletion of cognitive resources specific associated with selective attention. I demonstrated that these domain-specific resources can be depleted in a relatively short period of time (i.e., one-hour session). Moreover, I highlighted how emotional activation can either enhance or impair cognitive performance depending on the emotional valence of the stimuli involved, with negative emotions leading to detrimental effects and positive emotions leading to restorative effects on cognitive resources. I also provided evidence on the fact that under condition of high load on attentional processing, the active engagement of top-down behavioural control may limit, or even abolish, the detrimental effects of negative emotional stimuli.

In this doctoral dissertation three proposed approaches were evaluated using two databases of different languages, one American-English and one Greek. The proposed approaches were compared to the state-of-the-art models in the phone duration modelling task. The SVR model outperformed all the other individual models evaluated in this dissertation. Their ability to outperform all the other models is mainly based on their advantage of coping in a better way with high-dimensionality feature spaces in respect to the other models used in phone duration modelling, which makes them appropriate even for the case when the amount of the training data would be small respectively to the number of the feature set used. The proposed fusion scheme, taking advantage of the observation that different prediction algorithms perform better in different conditions, when implemented with SVR (SVR-fusion), contributed to the improvement of the phone duration prediction accuracy over that of the best individual model (SVR). Furthermore the SVR-fusion model managed to reduce the outliers in respect to the best individual model (SVR). Moreover, the proposed two-stage scheme using individual phone duration models as feature constructors in the first stage and feature vector extension (FVE) in the second stage, implemented with SVR (SVR-FVE), improved the prediction accuracy over the best individual predictor (SVR), and the SVR-fusion scheme and moreover managed to reduce the outliers in respect to the other two proposed schemes (SVR and SVR-fusion). The SVR two-stage scheme confirms in this way their advantage over all the other algorithms of coping well with high-dimensionality feature sets. The improved accuracy of phone duration modelling contributes to a better control of the prosody, and thus quality of synthetic speech. Furthermore, the first proposed method (SVR) was also evaluated on the phone duration modelling task in emotional speech, outperforming all the state-of-the-art models in all the emotional categories. Finally, perceptual tests were performed evaluating the impact of the proposed phone duration models to synthetic speech. The perceptual test for both the databases confirmed the results of objective tests showing the improvement achieved by the proposed models in the naturalness of synthesized speech.
Η παρούσα διδακτορική διατριβή πραγματεύεται προβλήματα που αφορούν στο χώρο της τεχνολογίας ομιλίας, με στόχο την μοντελοποίηση προσωδίας με χρήση τεχνικών μηχανικής μάθησης στα πλαίσια ουδέτερης και συναισθηματικής συνθετικής ομιλίας. Μελετήθηκαν τρεις καινοτόμες μέθοδοι μοντελοποίησης προσωδίας, οι οποίες αξιολογήθηκαν με αντικειμενικά τεστ και με υποκειμενικά τεστ ποιότητας ομιλίας για την συνεισφορά τους στην βελτίωση της ποιότητα της συνθετικής ομιλίας: Η πρώτη τεχνική μοντελοποίησης διάρκειας φωνημάτων, βασίζεται στην μοντελοποίηση με χρήση Μηχανών Υποστήριξης Διανυσμάτων (Support Vector Regression – SVR). Η μέθοδος αυτή δεν έχει χρησιμοποιηθεί έως σήμερα στην πρόβλεψη διάρκειας φωνημάτων. Η μέθοδος αυτή συγκρίθηκε και ξεπέρασε σε απόδοση όλες τις μεθόδους της επικρατούσας τεχνολογίας (state-of-the-art) στη μοντελοποίηση της διάρκειας φωνημάτων. Η δεύτερη τεχνική, βασίζεται στην μοντελοποίηση διάρκειας φωνημάτων με συνδυαστικό μοντέλο πολλαπλών προβλέψεων. Συγκεκριμένα, οι προβλέψεις διάρκειας φωνημάτων από ένα σύνολο ανεξάρτητων μοντέλων πρόβλεψης διάρκειας φωνημάτων χρησιμοποιούνται ως είσοδος σε ένα μοντέλο μηχανικής μάθησης, το οποίο συνδυάζει τις εξόδους από τα ανεξάρτητα μοντέλα πρόβλεψης και επιτυγχάνει μοντελοποίηση της διάρκειας φωνημάτων με μεγαλύτερη ακρίβεια, μειώνοντας επιπλέον και τα μεγάλα σφάλματα (outliers), δηλαδή τα σφάλματα που βρίσκονται μακριά από το μέσο όρο των σφαλμάτων. Η τρίτη τεχνική, είναι μια μέθοδος μοντελοποίησης διάρκειας φωνημάτων δύο σταδίων με κατασκευή νέων χαρακτηριστικών και επέκταση του διανύσματος χαρακτηριστικών. Συγκεκριμένα, στο πρώτο στάδιο, ένα σύνολο ανεξάρτητων μοντέλων πρόβλεψης διάρκειας φωνημάτων που χρησιμοποιούνται ως παραγωγοί νέων χαρακτηριστικών εμπλουτίζουν το διάνυσμα χαρακτηριστικών. Στο δεύτερο στάδιο, το εμπλουτισμένο διάνυσμα χρησιμοποιείται για να εκπαιδευτεί ένα μοντέλο πρόβλεψης διάρκειας φωνημάτων το οποίο επιτυγχάνει υψηλότερη απόδοση σε σχέση με όλες τις προηγούμενες μεθόδους, και μειώνει τα μεγάλα σφάλματα. Επιπλέον εφαρμόστηκε η πρώτη μέθοδος σε συναισθηματική ομιλία. Το προτεινόμενο SVR μοντέλο επιτυγχάνει την υψηλότερη απόδοση συγκρινόμενο με όλα τα state-of-the-art μοντέλα. Τέλος, πραγματοποιήθηκαν υποκειμενικά τεστ ποιότητας ομιλίας ώστε να αξιολογηθεί η συνεισφορά των τριών προτεινόμενων μεθόδων στη βελτίωση της ποιότητας της συνθετικής ομιλίας. Τα τεστ αυτά επιβεβαίωσαν την αξία των προτεινόμενων μεθόδων και τη συνεισφορά τους στη βελτίωση της ποιότητας στην συνθετική ομιλία.

Dissertação de mestrado integrado em Psicologia
Self-referential information has been shown to have a processing advantage over information relating to others. This effect was termed the self-reference effect (SRE) and has been investigated across various fields of cognitive function, such as visual word processing. Some studies have attempted to identify at which stage of lexical access the SRE occurs, although findings have been mixed. In this study we aimed to observe if self-referential information affects early stages of visual word recognition, with the use of a lexical decision task combined with a priming paradigm. Participants were asked to identify whether the presented stimuli were words or non-words, with target words that could be either positive (e.g., “attractive”), negative (e.g., “useless”) or neutral (e.g., “regular”). To explore the role of self-reference, target words were preceded by a brief prime (50 ms) that could be self-related (“Eu sou”[I am]), other-related (“Ela é”[She is]) or a control prime (“%%%%%”). Results showed a processing advantage of words preceded by self-related primes over other-related primes, demonstrating a SRE. However, post-hoc comparisons revealed that this effect was specific of negative words. Words preceded by control primes resulted in faster responses than other-related primes, suggesting a processing cost for other-referential information, which was especially true for neutral words. Our findings confirm that self-referential information has an impact on early stages of visual word recognition.
Informação autorreferenciada tem sido demonstrada como tendo vantagem de processamento em relação a informação sobre outras pessoas. Este efeito foi chamado de self-reference effect (SRE) e tem sido investigado em várias áreas do funcionamento cognitivo, tal como o processamento de palavras visuais. Alguns estudos tentaram identificar em que fase do acesso lexical acontece o SRE, mas os resultados têm sido mistos. Neste estudo procurámos observar se informação autorreferenciada afeta fases iniciais do reconhecimento de palavras visuais, através de uma tarefa de decisão lexical combinado com um paradigma de priming mascarado. Foi pedido às participantes para identificar se os estímulos apresentados eram palavras ou não palavras, com palavras alvo positivas (e.g., “atrativa”), negativas (e.g., “inútil”) ou neutras (e.g., “regular”). Para explorar o efeito da autorreferencia, as palavras alvo foram precedidas por um prime breve (50 ms) que podia ser self-related (“Eu sou”), other-related (“Ela é”) ou controlo (“%%%%%”). Os resultados mostraram uma vantagem de processamento de palavras precedidas por primes self-related em comparação com primes other-related, demonstrado o SRE. Contudo, comparações post-hoc revelaram que este efeito foi específico para palavras negativas. Palavras precedidas por primes de controlo resultaram em respostas mais rápidas do que primes other-related, o que sugere um custo de processamento para informação referente a outros. Isto foi particularmente evidente para palavras neutras. Estes resultados sugerem que informação autorreferenciada tem impacto em fases iniciais do reconhecimento de palavras visuais.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1989.
Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 212-237).

Dissertação de mestrado integrado em Psicologia
A memória de destino refere-se à capacidade de recordarmos a quem dissemos algo. As suas falhas devem-se ao facto de, ao transmitirmos uma informação, focarmos a nossa atenção em nós próprios e nos processos de transmissão dessa informação e não na pessoa a quem a destinamos. A emocionalidade do material parece torná-lo mais saliente, aumentando a atenção da pessoa para a informação, diminuindo consequentemente os recursos atencionais disponíveis para a associação face-facto. Este estudo pretendeu analisar o efeito da emocionalidade da informação na memória de destino. Quarenta participantes disseram frases neutras (e.g., “a janela é de madeira”), positivas (e.g., “a noiva está deslumbrante”) e negativas (e.g., “o funeral é amanhã”) a faces de desconhecidos. Posteriormente, realizaram dois testes de reconhecimento: um de memória de itens e outro de memória associativa. Os resultados mostraram melhor memória de destino quando as frases são emocionais em comparação com frases neutras. Quanto à memória de itens, verificamos que não existem diferenças no reconhecimento de frases emocionais (positivas e negativas) e frases neutras. Estes resultados contrariam as explicações da memória de destino que se baseiam no foco da atenção: a emocionalidade da informação favorece a memória de destino, mas não influencia a memória de itens.
Destination memory is the capacity to remember to whom we said something. Failures in this type of memory are due to, while transmitting information, attention being focused in ourselves and in the transmission processes rather than on the person to whom it is destined. Emotionality of the material appears to enhance its salience, increasing the person’s attention to the information, and consequently diminishing available attentional resources to the face-fact association. This study intended to analyse the effect of information emotionality in destination memory. Forty participants stated neutral (e.g., “the window is of wooden”), positive (e.g., “the bride is gorgeous”) and negative (e.g., “the funeral is tomorrow”) sentences to unknown faces. Thereafter, two recognition tests were performed by the participants: an item memory test and an associative memory test. Results showed better destination memory for emotional sentences, comparatively to neutral sentences. Regarding item memory, there were found no significant differences in recognition between emotional sentences (positive and negative) and neutral sentences. Current results contradict explanations of destination memory based on the attention focus: emotionality of the information enhances destination memory, but it does not influence item memory.

Il a été suggéré que lorsqu’une trace de mémoire consolidée est rappelée (réactivée), elle devient instable et sujette aux modifications avant de se stabiliser à nouveau en mémoire à long terme. Nous avons récemment démontré que lorsque la réactivation d’un souvenir négatif est couplée à l’exposition à un stress psychosocial, le souvenir de l’évènement négatif est augmenté de façon durable. En se basant sur ces résultats, le but de cette thèse est de préciser le rôle du stress psychologique et physiologique (hormones de stress) sur la modulation de souvenirs réactivés. Plus précisément, la première étude visait à déterminer si le cortisol, hormone de stress majeure, est un joueur clé dans la modulation des souvenirs réactivés. Pour ce faire, nous avons inhibé pharmacologiquement les niveaux de cortisol au moment de la réactivation d’un souvenir contenant des segments neutres et négatifs. Les résultats démontrent que la réactivation du matériel négatif est amoindrie lorsque les niveaux de cortisol sont inhibés, et cet effet est toujours présent quatre jours plus tard. Étant donné que les stimuli utilisés jusqu’à maintenant ont une faible validité écologique, nous avons voulu déterminer si d’autres types de mémoires pouvaient également être modulables lors de leur réactivation. L’objectif de la deuxième étude était donc de déterminer si les mémoires autobiographiques collectives sont modulables par le stress au moment de leur réactivation. Pour ce faire, nous avons exposé les participants à de vrais extraits de journaux, neutres ou négatifs, afin de réactiver les mémoires collectives associées à ces évènements. Par la suite, tous les participants ont été exposés à un stress psychosocial et leur mémoire des extraits a été évaluée la journée suivante. Les résultats démontrent que les femmes ayant lu les nouvelles négatives avaient une réactivité physiologique accrue face au stresseur et une mémoire augmentée de ces mêmes nouvelles le jour suivant. Ce phénomène n’était cependant pas observable chez les hommes. Le but de la troisième étude était de déterminer si les mémoires autobiographiques personnelles sont modulables par le stress au moment de leur réactivation. Nous avons demandé aux participants de se remémorer deux évènements de leur passé, négatifs ou neutres. Par la suite, ils ont été exposés à un stress psychosocial et leur mémoire pour ces mêmes évènements a été évaluée à nouveau la journée suivante. Les résultats démontrent que les mémoires autobiographiques personnelles réactivées ne semblent pas être modulables par l’exposition à un stresseur. Globalement, les résultats de cette thèse démontrent que le cortisol a la capacité de moduler des souvenirs négatifs réactivés, mais que la nature (extrinsèque vs. intrinsèque) et l'intensité des souvenirs réactivés sont des facteurs déterminants pour que ce phénomène prenne place.
It has been suggested that when a consolidated memory trace is recalled (reactivated), it becomes active and sensitive to modifications before stabilizing again in the long-term memory system. We have recently demonstrated that when the reactivation of a negative memory is followed by exposition to a psychosocial stressor, the memory for the negative material is enhanced in a long-lasting manner. Based on these results, the goal of this thesis is to clarify the role of physiological (stress hormones) and psychological stress on the modulation of reactivated memories. More precisely, the first study aimed to determine whether cortisol, a major stress hormone, is a key player in the modulation of reactivated memories. To do so, we have pharmacologically inhibited cortisol levels at the time of reactivating a memory composed of neutral and negative segments. Results showed that the reactivation of the negative material is decreased when cortisol levels are inhibited and this effect is still present four days later. Given that the stimuli used so far have a weak ecological validity, we wanted to determine whether other types of memories could also be modified upon their reactivation. The goal of the second study was to examine whether collective autobiographical memories were sensitive to the effects of stress at the time of reactivation. To do so, we have exposed participants to real newspaper excerpts, either neutral or negative, in order to reactivate the collective memories associated to these events. We have then exposed all the participants to a psychosocial stressor and their memory for the excerpts was assessed the following day. Results showed that women who have read negative news excerpts had a more pronounced physiological reactivity to the stressor and an increased memory for these news the following day. This phenomenon, however, was not observed in men. The goal of the third study was to determine whether personal autobiographical memories were sensitive to the effects of stress at the time of their reactivation. We have asked participants to recall two personal events, either negative or neutral. We then exposed them to a stressor and their memory for these events was tested the following day. The results showed that reactivated personal autobiographical memories were not sensitive to stress. Globally, the results of this thesis show that cortisol has the capacity to modulate reactivated negative memories, but that the nature (extrinsic vs. intrinsic) and the intensity of the memories are determining factors for this phenomenon to occur.