Modulation des souvenirs neutres et émotifs consolidés : rôle du stress et des hormones de stress

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

Sex and gender role differences on stress, depression, and anxiety symptoms in response to the COVID-19 pandemic over time

IntroductionStress, depression, and anxiety symptoms have been reported during the pandemic, with important inter-individual differences. Past cross-sectional studies have found that sex and gender roles may contribute to the modulation of one's vulnerability to develop such symptoms. This longitudinal study aimed to examine the interaction of sex and psychological gender roles on stress, depression, and anxiety symptoms in adults during the COVID-19 pandemic.MethodsFollowing the confinement measures in March 2020 in Montreal, stress, depression, and anxiety symptoms were assessed every 3 months (from June 2020 to March 2021) with the Depression, Anxiety and Stress Scale among 103 females and 50 males. Femininity and masculinity scores were assessed with the Bem Sex Role Inventory before the pandemic and were added as predictors along with time, sex, and the interactions between these variables using linear mixed models.ResultsWe observed similar levels of depressive symptoms between males and females, but higher levels of stress and anxious symptoms in females. No effects of sex and gender roles on depressive symptoms were found. For stress and anxiety, an interaction between time, femininity, and sex was found. At the beginning of the pandemic, females with high femininity had more stress symptoms than males with high femininity, whereas females with low femininity had more anxiety symptoms 1 year after the confinement measures compared to males with low femininity.DiscussionThese findings suggest that sex differences and psychological gender roles contribute to heterogeneous patterns of stress and anxiety symptoms over time in response to the COVID-19 pandemic

Ion stopping in dense plasma target for high energy density physics

The basic physics of nonrelativistic and electromagnetic ion stopping in hot and ionized plasma targets is thoroughly updated. Corresponding projectile-target interactions involve enhanced projectile ionization and coupling with target free electrons leading to significantly larger energy losses in hot targets when contrasted to their cold homologues. Standard stoppping formalism is framed around the most economical extrapolation of high velocity stopping in cold matter. Further elaborations pay attention to target electron coupling and nonlinearities due to enhanced projectile charge state, as well. Scaling rules are then used to optimize the enhanced stopping of MeV/amu ions in plasmas with electron linear densities nel ~ 10 18 -10 20 cm -2 . The synchronous firing of dense and strongly ionized plasmas with the time structure of bunched and energetic multicharged ion beam then allow to probe, for the first time, the long searched enhanced plasma stopping and projectile charge at target exit. Laser ablated plasmas (SPQR1) and dense linear plasma columns (SPQR2) show up as targets of choice in providing accurate and on line measurements of plasma parameters. Corresponding stopping results are of a central significance in asserting the validity of intense ion beam scenarios for driving thermonuclear pellets. Other applications of note feature thorium induced fission, novel ion sources and specific material processing through low energy ion beams. Last but not least, the given ion beam-plasma target interaction physics is likely to pave a way to the production and diagnostics of warm dense matter (WDM)

A transdisciplinary perspective of chronic stress in relation to psychopathology throughout life span development

The allostatic load (AL) model represents an interdisciplinary approach to comprehensively conceptualize and quantify chronic stress in relation to pathologies throughout the life cycle. This article first reviews the AL model, followed by interactions among early adversity, genetics, environmental toxins, as well as distinctions among sex, gender, and sex hormones as integral antecedents of AL. We next explore perspectives on severe mental illness, dementia, and caregiving as unique human models of AL that merit future investigations in the field of developmental psychopathology. A complimenting transdisciplinary perspective is applied throughout, whereby we argue that the AL model goes beyond traditional stress–disease theories toward the advancement of person-centered research and practice that promote not only physical health but also mental healt

Immediate and delayed effects of stress on a reactivitated declarative long-term memory trace

In 1968, a study demonstrated that consolidated memories can be affected again if they are reactivated. Given the importance of the stress hormones glucocorticoids (GCs) on memory consolidation, the goal of the current study was to assess whether GCs had the capacity to affect a reactivated long-term memory and whether neutral and emotional memories were affected differently. At the first session, participants encoded a movie containing neutral and emotional scenes. Two days later, they recalled the story. Half of them were then exposed to a psychosocial stressor. Memory performance was assessed again right after the stressor and five days later. The stressed group recalled less neutral material five days after the stressor compared to controls. Immediately after the stressor, the stressed group recalled more emotional material than controls. Moreover, this enhanced memory trace was maintained across time. This highlights the importance of minimizing exposure to stressful contexts when reactivating emotional memories

Articuler construction des savoirs, pratiques écrites et orales au lycée : le rôle du débat interprétatif délibératif en classe de français

International audienc

Articuler construction des savoirs, pratiques écrites et orales au lycée : le rôle du débat interprétatif délibératif en classe de français

International audienc