Neural mechanisms of reactivation-induced updating that enhance and distort memory

We remember a considerable number of personal experiences because we are frequently reminded of them, a process known as memory reactivation. Although memory reactivation helps to stabilize and update memories, reactivation may also introduce distortions if novel information becomes incorporated with memory. Here we used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms mediating reactivation-induced updating in memory for events experienced during a museum tour. During scanning, participants were shown target photographs to reactivate memories from the museum tour followed by a novel lure photograph from an alternate tour. Later, participants were presented with target and lure photographs and asked to determine whether the photographs showed a stop they visited during the tour. We used a subsequent memory analysis to examine neural recruitment during reactivation that was associated with later true and false memories. We predicted that the quality of reactivation, as determined by online ratings of subjective recollection, would increase subsequent true memories but also facilitate incorporation of the lure photograph, thereby increasing subsequent false memories. The fMRI results revealed that the quality of reactivation modulated subsequent true and false memories via recruitment of left posterior parahippocampal, bilateral retrosplenial, and bilateral posterior inferior parietal cortices. However, the timing of neural recruitment and the way in which memories were reactivated contributed to differences in whether memory reactivation led to distortions or not. These data reveal the neural mechanisms recruited during memory reactivation that modify how memories will be subsequently retrieved, supporting the flexible and dynamic aspects of memory

Réflexions sur un terrain particulier : La vente de garage

S’appuyant sur un terrain mené depuis plus de trois ans dans différentes villes du Québec, cette note de recherche présente les réflexions de Geneviève St-Jacques Thériault sur le phénomène des ventes de garage. Son projet de maîtrise, entamé depuis septembre 2003, vise à comprendre ce que cette activité représente pour les participants, ainsi que les valeurs qui se dégagent de cette pratique. Différents concepts utiles à l’étude de ce phénomène seront abordés : la forme festive et rituelle, l’économie informelle, le jeu et, finalement, les interactions présentes lors de cette activité. Il sera finalement question du marchandage, interaction qui met en place des préoccupations rituelles, économiques et ludiques.Based on fieldwork conducted over the last three years in several cities across Québec, this research note presents the ideas of Geneviève St-Jacques Thériault regarding the garage sale phenomenon. Her Master’s degree project, begun in September 2003, aims to understand what the activity represents for participants and the values that arise from this practice. A number of useful concepts that are part of this study will be discussed: the festive and ritual aspect, the informal economy, the “game”, and the interactions that are part of the activity. It is, in the end, all about the art of haggling, which is an interaction that incorporates ritual, economic and leisure concerns

Information capacity of the Hopfield model

The information capacity of general forms of memory is formalized. The number of bits of information that can be stored in the Hopfield model of associative memory is estimated. It is found that the asymptotic information capacity of a Hopfield network of N neurons is of the order N^3b. The number of arbitrary state vectors that can be made stable in a Hopfield network of N neurons is proved to be bounded above by N

Shifting visual perspective during memory retrieval reduces the accuracy of subsequent memories

Memories for events can be retrieved from visual perspectives that were never experienced, reflecting the dynamic and reconstructive nature of memories. Characteristics of memories can be altered when shifting from an own eyes perspective, the way most events are initially experienced, to an observer perspective, in which one sees oneself in the memory. Moreover, recent evidence has linked these retrieval-related effects of visual perspective to subsequent changes in memories. Here we examine how shifting visual perspective influences the accuracy of subsequent memories for complex events encoded in the lab. Participants performed a series of mini-events that were experienced from their own eyes, and were later asked to retrieve memories for these events while maintaining the own eyes perspective or shifting to an alternative observer perspective. We then examined how shifting perspective during retrieval modified memories by influencing the accuracy of recall on a final memory test. Across two experiments, we found that shifting visual perspective reduced the accuracy of subsequent memories and that reductions in vividness when shifting visual perspective during retrieval predicted these changes in the accuracy of memories. Our findings suggest that shifting from an own eyes to an observer perspective influences the accuracy of long-term memories

Attraction et rétention des immigrants récents hors Montréal : une analyse longitudinale par cohorte d’arrivée au Québec (1992, 1996, 2000 et 2004)

Cette étude s’intéresse à l’évolution de la capacité du Québec hors Montréal à attirer et retenir les immigrants depuis l’introduction d’un axe de régionalisation dans la politique québécoise d’immigration au début des années 1990. À partir d’une exploitation longitudinale du Fichier d’inscription des personnes assurées de la Régie de l’assurance maladie du Québec, nous avons reconstruit jusqu’en 2007 les trajectoires résidentielles de quatre cohortes d’immigrants admises au Québec entre 1992 et 2004. Nos résultats montrent que la présence d’immigrants hors Montréal est davantage tributaire du choix du premier lieu de résidence que de la migration secondaire interne. Tant la répartition initiale que les échanges migratoires subséquents ont toutefois connu des changements profitables au Québec hors Montréal qui reçoit une part accrue des nouveaux immigrants et qui est devenu plus attractif auprès des immigrants de Montréal. Les résultats précisent aussi qu’à l’extérieur de Montréal, ce sont les principaux centres urbains (Québec, Gatineau et Sherbrooke) qui exercent la plus forte attraction, mais que des agglomérations de taille plus réduite ont considérablement amélioré leur bilan.This article examines the evolution of the capacity of the areas of Québec outside Montréal to attract and retain immigrants since initiatives for regionalization became part of Québec’s immigration policy at the beginning of the 1990s. Through the longitudinal use of FIPA, the insured persons registration file of the Régie de l’assurance maladie du Québec, we reconstructed up until 2007 the residential trajectories of four immigrant cohorts admitted to Québec between 1992 and 2004. Our findings show that the presence of immigrants outside Montréal depends more on the choice of first place of residence than on internal secondary migration. However, both initial distribution and subsequent migratory exchanges with Montréal profited the rest of Québec, which welcomed a higher share of new immigrants and became more attractive to Montréal immigrants. The findings also show that outside Montréal it is the main urban centres (Québec, Gatineau and Sherbrooke) that are exerting the strongest pull on immigrants but that smaller urban areas have improved their situations considerably

Notion, objectifs, possibilités

Après avoir défini la notion de politique de salaires, l'auteur tente d'en expliquer les objectifs et d'identifier les moyens à employer pour la rendre efficace. Mais, en fait, on parle beaucoup de politique de salaires mais que fait-on concrètement à ce sujet