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Selon Tulving, la mémoire épisodique regroupe l’ensemble des événements que nous avons personnellement expérimentés, et nous offre la possibilité de faire un voyage mental dans le passé, ou dans le futur, rien qu’en y repensant. Les troubles de la mémoire épisodique font parties des troubles neuropsychologiques qui sont les plus fréquemment rencontrés et ceux-ci ont de lourdes conséquences sur le quotidien des individus. Il semble donc nécessaire que les professionnels possèdent des épreuves qui permettent de mesurer ce système de mémoire de manière adéquate. Cependant, les épreuves neuropsychologiques classiques évaluant cette mémoire, telles que les listes de mots, ne correspondent pas entièrement aux difficultés que les patients peuvent rencontrer dans leur vie quotidienne (Chaytor & Schmitter-Edgecombe, 2003). Afin de contrer cette limite de validité écologique, nous avons créé une épreuve en réalité virtuelle. Cette recherche a pour objectif d’utiliser les avantages de la réalité virtuelle afin de proposer une évaluation écologique de la mémoire épisodique.

Episodic memory --- Virtual Reality --- Mémoire épisodique --- Réalité virtuelle --- Sciences sociales & comportementales, psychologie > Traitement & psychologie clinique

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The CA3 hippocampal region receives information from the entorhinal cortex either directly from the perforant path or indirectly from the dentate gyrus via the mossy fibers (MFs). According to their specific targets (principal/mossy cells or interneurons), MFs terminate with large boutons or small filopodial extensions, respectively. MF-CA3 synapses are characterized by a low probability of release and pronounced frequency-dependent facilitation. In addition MF terminals are endowed with mGluRs that regulate their own release. We will describe the intrinsic membrane properties of pyramidal cells, which can sometimes fire in bursts, together with the geometry of their dendritic arborization. The single layer of pyramidal cells is quite distinct from the six-layered neocortical arrangement. The resulting aligned dendrites provides the substrate for laminated excitatory inputs. They also underlie a precise, diversity of inhibitory control which we will also describe in detail. The CA3 region has an especially rich internal connectivity, with recurrent excitatory and inhibitory loops. In recent years both in vivo and in vitro studies have allowed to better understand functional properties of the CA3 auto-associative network and its role in information processing. This circuit is implicated in encoding spatial representations and episodic memories. It generates physiological population synchronies, including gamma, theta and sharp-waves that are presumed to associate firing in selected assemblies of cells in different behavioral conditions. The CA3 region is susceptible to neurodegeneration during aging and after stresses such as infection or injury. Loss of some CA3 neurones has striking effects on mossy fiber inputs and can facilitate the generation of pathologic synchrony within the CA3 micro-circuit. The aim of this special topic is to bring together experts on the cellular and molecular mechanisms regulating the wiring properties of the CA3 hippocampal microcircuit in both physiological and pathological conditions, synaptic plasticity, behavior and cognition. We will particularly emphasize the dual glutamatergic and GABAergic phenotype of MF-CA3 synapses at early developmental stages and the steps that regulate the integration of newly generated neurons into the adult dentate gyrus-CA3 circuit.

Hippocampus (Brain) --- Hippocampus (Brain) --- Neurobiology. --- Neurosciences. --- episodic memory --- mossy fibers --- Associative network --- spatial representation --- CA3 subfield --- Hippocampus --- Theta Rhythm --- Physiology. --- episodic memory --- mossy fibers --- Associative network --- spatial representation --- CA3 subfield --- Hippocampus --- Theta Rhythm

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The CA3 hippocampal region receives information from the entorhinal cortex either directly from the perforant path or indirectly from the dentate gyrus via the mossy fibers (MFs). According to their specific targets (principal/mossy cells or interneurons), MFs terminate with large boutons or small filopodial extensions, respectively. MF-CA3 synapses are characterized by a low probability of release and pronounced frequency-dependent facilitation. In addition MF terminals are endowed with mGluRs that regulate their own release. We will describe the intrinsic membrane properties of pyramidal cells, which can sometimes fire in bursts, together with the geometry of their dendritic arborization. The single layer of pyramidal cells is quite distinct from the six-layered neocortical arrangement. The resulting aligned dendrites provides the substrate for laminated excitatory inputs. They also underlie a precise, diversity of inhibitory control which we will also describe in detail. The CA3 region has an especially rich internal connectivity, with recurrent excitatory and inhibitory loops. In recent years both in vivo and in vitro studies have allowed to better understand functional properties of the CA3 auto-associative network and its role in information processing. This circuit is implicated in encoding spatial representations and episodic memories. It generates physiological population synchronies, including gamma, theta and sharp-waves that are presumed to associate firing in selected assemblies of cells in different behavioral conditions. The CA3 region is susceptible to neurodegeneration during aging and after stresses such as infection or injury. Loss of some CA3 neurones has striking effects on mossy fiber inputs and can facilitate the generation of pathologic synchrony within the CA3 micro-circuit. The aim of this special topic is to bring together experts on the cellular and molecular mechanisms regulating the wiring properties of the CA3 hippocampal microcircuit in both physiological and pathological conditions, synaptic plasticity, behavior and cognition. We will particularly emphasize the dual glutamatergic and GABAergic phenotype of MF-CA3 synapses at early developmental stages and the steps that regulate the integration of newly generated neurons into the adult dentate gyrus-CA3 circuit.

Hippocampus (Brain) --- Hippocampus (Brain) --- Neurobiology. --- Neurosciences. --- Physiology. --- episodic memory --- mossy fibers --- Associative network --- spatial representation --- CA3 subfield --- Hippocampus --- Theta Rhythm

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Researchers working in many fields of psychology and neuroscience are interested in the temporal structure of experience, as well as the experience of time, at scales of a few milliseconds up to a few seconds as well as days, months, years, and beyond. This Research Topic supposes that broadly speaking, the field of “time psychology” can be organized by distinguishing between “perceptual” and “conceptual” time-scales. Dealing with conceptual time: “mental time travel,” also called mental simulation, self-projection, episodic-semantic memory, prospection/foresight, allows humans (and perhaps other animals) to imagine and plan events and experiences in their personal futures, based in large part on memories of their personal pasts, as well as general knowledge. Moreover, contents of human language and thought are fundamentally organized by a temporal dimension, enmeshed with it so thoroughly that it is usually expressible only through spatial metaphors. But what might such notions have to do with experienced durations of events lasting milliseconds up to a few seconds, during the so-called “present moment” of perception-action cycle time? This Research Topic is organized around the general premise that, by considering how mental time travel might “scale down” to time perception (and vice-versa, no less), progress and integrative synthesis within- and across- scientific domains might be facilitated. Bipolar configurations of future- and past-orientations of the self may be repeated in parallel across conceptual and perceptual time-scales, subsumed by a general “Janus-like” feed forward feedback system for goal-pursuit. As an example, it is notable that the duality of “prospection”and semantic-episodic memory operating at conceptual time-scales has an analogue inperception-action cycle time, namely the interplay of anticipatory attention and working memory.

Time perception --- Neurosciences --- Psychological aspects. --- Research. --- episodic memory --- Time Perception --- Consciousness --- working memory --- Attention --- mind wandering --- prospection --- mental time travel

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Les études sur l’utilisation de la réalité virtuelle (RV) pour augmenter la validité écologique des tâches de mémoire épisodique sont de plus en plus fréquentes dans la littérature scientifique. Cet outil permettrait de mesurer les deux versants de la validité écologique, à savoir la vérisimilitude et la véridicalité. L’objectif de ce mémoire est donc de rendre compte de l’intérêt d’utiliser une évaluation de la mémoire épisodique basée sur la RV pour prendre en considération ces deux concepts et ainsi de tenir compte du fonctionnement des patients dans la vie quotidienne. En effet, nous allons tenter de dépasser dans ce travail, une limite des tests classiques de mémoire que les neuropsychologues utilisent couramment.
D’une part, nous avons fait l’hypothèse d’une meilleure vérisimilitude de la tâche de mémoire se basant sur le RV par rapport à une tâche de mémoire traditionnelle. Nous avons mesuré le sentiment de présence et d’immersion, l’absence de cybermalaises ainsi que, secondairement, la validité théorique et les fonctions exécutives. D’autre part, nous faisions l’hypothèse d’une meilleure véridicalité.
Pour réaliser cette étude, 13 sujets cliniques appariés à 13 sujets contrôles ont été recrutés. Une tâche mnésique en RV avec un ordinateur et un joystick, une auto-évaluation des plaintes et des tests neuropsychologiques ont été administrés durant deux séances.
Les résultats provenant de cette recherche ont montré une bonne validité convergente et discriminante de la tâche mnésique en RV. Cependant, un manque de vérisimilitude et un manque de véridicalité ont pu être mis en évidence, ne permettant pas de répondre à notre hypothèse d’une meilleure validité écologique en RV. Hypothétiquement, ces résultats pourraient provenir d’un manque de sentiment de présence et d’immersion, de difficultés exécutives et/ou de familiarisation, d’une absence d’une meilleure validité théorique pour la tâche en RV, du choix de certaines évaluations et, finalement, d’un manque de sujets au sein de cette étude.
En conclusion, nous voyons un intérêt certains de l’utilisation d’une évaluation plus écologique de la mémoire épisodique grâce à la RV. Néanmoins, de nombreux paramètres devraient être pris en compte. Une réplication de cette étude, avec davantage de participants, serait donc nécessaire pour tenter de répondre à l’hypothèse de la validité écologique.

Mémoire épisodique --- Réalité virtuelle --- Evaluation --- Episodic memory --- Virtual reality --- Assessment --- Sciences sociales & comportementales, psychologie > Psychologie cognitive & théorique