Relational memory refers to memory for arbitrary associations among components of experience, and is thought to be critically dependent on the hippocampus. Previous studies suggested that age-related differences in relational memory were consistent with a protracted developmental trajectory of hippocampus. Recently, eye tracking studies conducted in infants have concluded that eye movement detection could provide one indirect index of relational memory and hippocampal function in infants as young as 6 months. While the eye-based memory expression has been detected in adults on relational memory tasks, this effect has been less studied across development, and the few studies that have been conducted have suggested discontinuity in eye-movement behaviors across age. The purpose of the current study is to examine the development of relational memory in middle childhood (7-8 years of age) by utilizing a face-scene binding paradigm. Behavioral results revealed that adults showed higher identification accuracy than children when recalling matching faces based on scene cues. The eye movement data indicated that adults showed stronger and more rapid looking preference to matching face during correct test trials, and the proportion of viewing time towards matching face was significantly greater than children on incorrect trials (while performance was below chance in both age groups). Therefore, eye movements do index relational memory and correct responses but show rapid onset only in adults. We discuss these results in the context of the neural systems that may support eye movement behavior across the lifespan and conclude that more work is required to determine the nature and strength of these effects prior to adopting eye-movements as a continuous measure of relational memory across development.

By using eye movement monitoring (EMM) techniques, investigators have been able to examine the processes that support relational memory as they occur online. However, EMM studies have only focused on memory for spatial relations, producing a lack of EMM evidence for temporal relations. Thus, in the present study, participants performed a recognition memory task with stimuli that varied in their spatial and temporal relations. They were presented with a sequence of objects in a unique spatial configuration, and were instructed to either detect changes in the spatial or temporal relations between study and test presentations. The results provide novel EMM evidence for an interaction between spatial and temporal memory, and the obligatory effects of relational memory processes on eye movement behaviours. Moreover, the current study was also able to test predictions from the temporal context model (Howard & Kahana, 2002), and found evidence for a temporal contiguity effect.

Theories of age-related memory decline debate whether the problem lies at the level of encoding or consciously accessing information at the level of retrieval. Deficits at encoding may be due to the inability to bind relations among objects. The present research implements eye movement monitoring into an associative memory task to explore age-related memory at encoding and retrieval. Eye movements of older and younger adults are compared. Three solitary items were presented during the study phase, and test responses were whether the spatial relation of these objects to one another was intact or manipulated when subsequently presented all together. Observed differences at the level of encoding in addition to the level of retrieval clarifies that there is not a deficit in consciously accessing encoded representations. Further, differences in relational binding at the level of encoding were observed, which supports the association deficit theory of memory and aging.

By using eye movement monitoring (EMM) techniques, investigators have been able to examine the processes that support relational memory as they occur online. However, EMM studies have only focused on memory for spatial relations, producing a lack of EMM evidence for temporal relations. Thus, in the present study, participants performed a recognition memory task with stimuli that varied in their spatial and temporal relations. They were presented with a sequence of objects in a unique spatial configuration, and were instructed to either detect changes in the spatial or temporal relations between study and test presentations. The results provide novel EMM evidence for an interaction between spatial and temporal memory, and the obligatory effects of relational memory processes on eye movement behaviours. Moreover, the current study was also able to test predictions from the temporal context model (Howard & Kahana, 2002), and found evidence for a temporal contiguity effect.

Theories of age-related memory decline debate whether the problem lies at the level of encoding or consciously accessing information at the level of retrieval. Deficits at encoding may be due to the inability to bind relations among objects. The present research implements eye movement monitoring into an associative memory task to explore age-related memory at encoding and retrieval. Eye movements of older and younger adults are compared. Three solitary items were presented during the study phase, and test responses were whether the spatial relation of these objects to one another was intact or manipulated when subsequently presented all together. Observed differences at the level of encoding in addition to the level of retrieval clarifies that there is not a deficit in consciously accessing encoded representations. Further, differences in relational binding at the level of encoding were observed, which supports the association deficit theory of memory and aging.

Semantic memory includes vocabulary and word meanings, conceptual information, and general facts about the world (Tulving, 1972). According to the standard view of semantic memory in cognitive neuroscience, the hippocampus is necessary to first acquire new semantic information (Gabrieli, Cohen, & Corkin, 1988), but these representations are then consolidated in the neocortex and become independent of the hippocampus with time (McClelland, McNaughton, & O'Reilly, 1995). Remote semantic memory is considered independent of the hippocampus, and the hippocampus is not thought to play a critical role in the processing and use of such representations. The current work challenges the notion that previously acquired semantic knowledge, and its use during communication, is independent of the hippocampus. A group of patients with bilateral hippocampal damage and severe impairments in declarative memory were tested. Intact naming and word-definition matching performance in amnesia, has led to the notion that remote semantic memory is intact in patients with hippocampal amnesia. Motivated by perspectives of word learning as a protracted process where additional features and senses of a word are added over time, and by recent discoveries about the time course of hippocampal contributions to on-line relational processing, reconsolidation, and the flexible integration of information, we revisit the notion that remote semantic memory is intact in amnesia. Using measures of semantic richness and vocabulary depth from psycholinguistics and first and second language-learning studies, we examined how much information is associated with previously acquired, highly familiar words in hippocampal amnesic patients. Relative to healthy demographically matched comparison participants and a group of brain-damaged comparison participants, the patients with hippocampal amnesia performed significantly worse on both productive and receptive measures of vocabulary depth and semantic richness. In the healthy brain, semantic memory appears to get richer and deeper with time. Healthy participants of all ages were tested on these measures and strong correlations are seen with age as older healthy adults displayed richer semantic knowledge than the younger adults. The patient data provides a mechanism: hippocampal relational binding supports the deepening and enrichment of knowledge over time. These findings suggest that remote semantic memory is impoverished in patients with hippocampal amnesia and that the hippocampus supports the maintenance and updating of semantic memory beyond its initial acquisition. The use of lexical and semantic knowledge during discourse was also examined. Amnesic patients displayed significantly lower levels of lexical diversity in the speech they produced, and showed a strong trend toward producing language with reduced levels of semantic detail suggesting that patients cannot use their semantic representations as richly during communication. These results add to a growing body of work detailing a role for the hippocampus in language processing more generally. By documenting a role for the hippocampus in maintaining, updating, and using semantic knowledge, this work informs theories of semantic memory and it's neural bases, advances knowledge of the role of the hippocampus in supporting human behavior, and brings more sensitive measures to the neuroscientific study of semantic memory.

Research shows that emotional items are associated with enhanced processing and memory. However, emotional memories are composed of not only memory for the specific emotion-eliciting item, but also other items associated with it, as well as memory for how these items are related. The current thesis utilized verbal report, eye movement monitoring and magnetoencephalography in order to examine how emotions may influence online processing and memory for associated information. It was found that while emotions influenced attention to both the emotion-eliciting item and associated information during the encoding stage, this was not related to subsequent memory performance as indexed by verbal report. It was also found that while emotions impaired detailed memory for associated information, it did not affect the ease or speed at which those memories could be accessed. In using MEG, it was found that emotions may modulate not only how participants’ view associated information, but it may also modulate the type of representation formed. Together, findings from the current work suggests that: (1) emotions influence online processing and memory for associated information; (2) emotions modulate memory for associated information via routes other than overt attention; (3) encoding and retrieval may occur in stages; and (4) memory exerts early influences on processing. The current work shows that emotions modulate online processing of associated neutral information in a top-down manner, independent of differences in its physical properties. Work from this thesis encourages a reconceptualization of emotion, memory and perception and how they relate to one and another. Rather than viewing them as independent modular processes, they may, in fact, be more widely distributed in the brain and interact more closely than previously described. This may be evolutionarily adaptive allowing us to quickly and efficiently form memories for emotional events/scenes that can later guide perception and behaviour.

Research shows that emotional items are associated with enhanced processing and memory. However, emotional memories are composed of not only memory for the specific emotion-eliciting item, but also other items associated with it, as well as memory for how these items are related. The current thesis utilized verbal report, eye movement monitoring and magnetoencephalography in order to examine how emotions may influence online processing and memory for associated information. It was found that while emotions influenced attention to both the emotion-eliciting item and associated information during the encoding stage, this was not related to subsequent memory performance as indexed by verbal report. It was also found that while emotions impaired detailed memory for associated information, it did not affect the ease or speed at which those memories could be accessed. In using MEG, it was found that emotions may modulate not only how participants’ view associated information, but it may also modulate the type of representation formed. Together, findings from the current work suggests that: (1) emotions influence online processing and memory for associated information; (2) emotions modulate memory for associated information via routes other than overt attention; (3) encoding and retrieval may occur in stages; and (4) memory exerts early influences on processing. The current work shows that emotions modulate online processing of associated neutral information in a top-down manner, independent of differences in its physical properties. Work from this thesis encourages a reconceptualization of emotion, memory and perception and how they relate to one and another. Rather than viewing them as independent modular processes, they may, in fact, be more widely distributed in the brain and interact more closely than previously described. This may be evolutionarily adaptive allowing us to quickly and efficiently form memories for emotional events/scenes that can later guide perception and behaviour.

Une mémoire émotionnelle normale se base sur la sélection de stimuli prédictifs d’un événement important pour l’individu. Cependant, ce processus de sélection peut être compromis en situation de forte intensité émotionnelle. En particulier, la sélection d’un élément saillant non nécessairement prédictif, associée à une amnésie de type déclaratif pour les éléments contextuels, caractérise les altérations mnésiques de l’état de stress post-traumatique (ESPT). Les données de la littérature suggèrent que l’action de glucocorticoïdes dans l’hippocampe serait l’une des causes possibles du développement de troubles mnésiques de type ESPT. Nos travaux ont porté sur les conditions dans lesquelles les glucocorticoïdes dans l’hippocampe peuvent altérer les fonctions mnésiques chez la souris.En utilisant des procédures de conditionnement classique aversif, nous montrons que l’injection post-apprentissage de corticostérone dans l’hippocampe dorsal, en situation de forte intensité émotionnelle, conduit (1) à une sélection incorrecte du stimulus saillant non prédictif du choc électrique au détriment des éléments contextuels (2) et à des dysfonctionnements d’activité neuronale au sein du circuit hippocampo-amygdalien (expression de c-Fos). De façon intéressante, par une action sur le même type de récepteurs (aux glucocorticoïdes, GR), l’injection de corticostérone dans l’hippocampe ventral conduit également à un processus incorrect de sélection du stimulus prédictif mais en faveur des éléments contextuels. Enfin, un apprentissage en labyrinthe radiaire révèle que l’injection de corticostérone dans l’hippocampe dorsal altère spécifiquement la mémoire relationnelle, analogue de la mémoire déclarative humaine, uniquement chez les animaux ayant été au préalable exposés à un stress.L’ensemble de nos données révèlent qu’un excès de glucocorticoïdes dans l’hippocampe contribue (1) à des déficits de mémoires émotionnelle et relationnelle, (2) à la sélection inadaptée de stimuli non prédictifs d’un événement aversif (3) reposant sur des dysfonctionnements du circuit hippocampo-amygdalien, le tout, correspondant à des altérations mnésiques de type ESPT. / Normal emotional memory is based on the selection of cues predicting threatening events. However, exposure to extreme threatening situation can compromise the selection of the correct cues. In particular, selection of a salient not necessarily predictive cue, associated with declarative amnesia for peritraumatic contextual cues, characterizes the memory disturbances of posttraumatic stress disorder (PTSD). Accumulating evidence suggest that action of glucocorticoids into the hippocampus could be a potential mechanism for PTSD-related memory disturbances. Hence, we studied the conditions for which glucocorticoids into the hippocampus can alter memory functions in mice.Using Pavlovian fear conditioning, we showed that post-training infusion of glucocorticoids in the dorsal hippocampus, in stressful situation, resulted in (1) selection of a salient non predictive cue instead of contextual cues and in (2) dysfunctions of neural activity of the hippocampal-amygdalar circuit (c-Fos expression). Interestingly, via action on the same receptor subtype (glucocorticoid receptors, GR), infusion of glucocorticoids in the ventral hippocampus also resulted in incorrect selection of predictive cue but in favor of contextual cues. Finally, using radial-maze task, we showed that infusion of glucocorticoids in the dorsal hippocampus specifically impaired relational declarative-like memory, only in mice previously exposed to stress.Altogether, our findings reveal that excess glucocorticoids in the hippocampus contributes to (1) deficits in emotional and relational memories, (2) incorrect selection of predictive cues (3) based to dysfunctions of the hippocampal-amygdalar circuit, all, corresponding to PTSD-related memory disturbances.

La recherche des dernières décennies nous a offert une compréhension détaillée des processus par lesquels les aires visuelles du cerveau reconstituent les signaux physiques de l’environnement pour en générer des représentations. Cependant, la proposition selon laquelle la perception serait également le produit d’inférences et attentes, qui nous permettraient d’interpréter plus exactement les informations entrantes à l’aide d’expériences passées, est récurrente dans l’histoire des neurosciences cognitives. Le predictive coding (PC), qui est actuellement un modèle influent de la perception, propose qu’un des rôles principaux du cerveau est de prédire les informations entrantes. L’apprentissage visuel serait ainsi orienté en fonction d’informations n’ayant pas été correctement prédites ou d’erreurs de prédiction. Le PC est associé depuis quelques années par le phénomène de suppression neuronale (SN), où la réduction graduelle de l’activité cérébrale associée au traitement répété d’un stimulus, représenterait la réduction des erreurs de prédiction. Cette thèse propose premièrement que bien que la SN puisse être le reflet d’un processus assimilable au PC, celle-ci ne le représente possiblement qu’en partie. Une mesure additionnelle reflétant la correction ou l’ajustement des prédictions déclenché par l’erreur de prédiction serait alors nécessaire. Dans un premier temps, une revue critique des principaux courants de la recherche sur l’apprentissage est présentée sous la forme d’un chapitre de livre du domaine plus large du développement des capacités d’apprentissage. Celle-ci permet de préciser les aspects fondamentaux de l’habituation, la SN et la capacité à associer des éléments en mémoire, ainsi que l’importance de caractériser ces phénomènes aussi pleinement que possible par l’utilisation de nouvelles mesures, ce qui motive les études expérimentales présentées subséquemment. Par la suite, une première étude visant à identifier une mesure complémentaire à celle de la SN reflétant un processus d’ajustement de prédictions est présentée. Cette mesure, nommée entropie multi-échelles (EME), offre une estimation de la quantité d’information d’un signal électroencéphalographique (EEG) et de la capacité de traitement des réseaux neuronaux sous-jacents. La première hypothèse de cette étude était donc que la SN serait accompagnée d’une augmentation de l’EME au-dessus de la région occipito-temporale lors d’un apprentissage de visages. Puisque les phénomènes reflétés par la SN et l’EME s’appuieraient sur la contribution de régions distantes dont le cortex préfrontal dorsolatéral, la deuxième hypothèse était que ces mesures seraient altérées par une modulation exogène de l’activité de cette région préfrontale par stimulation électrique transcrânienne à courant direct (SETCD). Les résultats ont montré que le signal EEG présentait à la fois une SN et une augmentation de l’EME avec l’apprentissage. De plus, la modulation préfrontale par SETCD a entraîné des variations de l’EME de la région occipito-temporale, sans toutefois avoir un impact sur la mesure de SN. La première étude suggère ainsi que la SN et l’EME reflètent des mécanismes cérébraux impliqués dans l’apprentissage visuel et compatibles au modèle de PC. Dans la deuxième étude, l’hypothèse d’une association entre les mesures de SN et d’EME a été reprise, cette fois dans le contexte d’un apprentissage visuel relationnel, étant donné le potentiel que représente les connaissances d’associations passées entre items pour la génération de prédictions. Dans ce contexte, des effets de SN et d’augmentation d’EME ont été obtenus à nouveau et étaient associées à la réussite de l’encodage d’associations de visages-paysages. Un deuxième aspect de cette étude visait à investiguer la présence d’effets semblables chez de jeunes enfants sains, étant donné plusieurs études suggérant que le PC et la mémoire relationnelle soient fonctionnels dans la première année de vie. Cependant, étant donné l’absence d’effets dans ce groupe, les résultats de la deuxième étude suggèrent que la présence du PC tôt dans le développement s’appuie possiblement sur d’autres ressources que la mémoire relationnelle. Les études de cette thèse sont une première démonstration du potentiel que représentent les mesures de SN et d’EME dans la compréhension des mécanismes qui sous-tendent la perception et l’apprentissage visuel. / Research over the last decades has offered detailed knowledge of the processes by which visual areas use physical signals from the environment to represent it accurately. However, the proposition that perception also relies on inferences and predictions based on past experience to allow more efficiency in the interpretation of incoming signals has been recurrent throughout the history of cognitive neuroscience. In recent years, the predictive coding (PC) model, which proposes that the brain acts as a predictor of incoming information, has been influential in this field. Learning is therefore driven by prediction error and encoding is essentially restricted to unpredicted inputs, thus allowing adjustments to predictions. PC has been associated with repetition suppression (RS), whereby the gradual reduction in brain responses associated with the repeated processing of a stimulus is thought to represent prediction error reduction. This thesis proposes that although RS may be attributable to a PC process, it may not represent it fully. To do so would necessitate the use of an additional measure reflecting prediction adjustments carried out as a consequence of prediction error. A critical review of the principal currents in the cerebral mechanisms underlying learning is presented first. This review underlines the fundamental aspects of habituation, RS and the ability to associate elements to one another in memory and the importance of characterizing these phenomena fully using new measures of learning, which motivates the experimental studies presented next. Then, a study aimed at identifying a measure complementary to RS and reflecting a prediction adjustment process is presented. This measure, named multiscale entropy (MSE), offers an estimation of the information content of an electroencephalogram (EEG), and of the underlying neural networks. The first study’s main hypothesis was that RS would be accompanied with an increase in MSE over occipito-temporal areas during learning of faces. As the processes reflected by these measures would rely on distal contributions including the dorsolateral prefrontal cortex (DLPFC), the second hypothesis was that exogenous modulation of this region using transcranial direct current stimulation (tDCS) would alter RS and MSE effects found over occipito-temporal cortex. As predicted by hypotheses, EEG signal showed both RS and MSE increase from the first presentation of a face to the second over occipito-temporal sites. Additionally, prefrontal tDCS modulated brain signal complexity over right occipito-temporal cortex during learning, but did not influence RS over the same region. The first study therefore suggests that RS and MSE reflect mechanisms involved in learning of visual stimuli that appear compatible with the PC account of perception and learning. In the second study the hypothesis of an association between RS and MSE increase was investigated again, this time in the context of a visual relational memory task, given the high potential past associations of items represent for prediction generation. In this context, RS and MSE increase effects were replicated in study trials leading to correct associations of face-landscape pairings. The second study also investigated the presence of similar effects in a sample of young healthy children, given that recent studies have found evidence of both PC mechanisms and relational memory ability emerging in the first year of life. However, given the lack of effects in this sample of participants, we suggest that while PC mechanisms may emerge early, relational memory may contribute later in the course of development. Together, the studies presented in this thesis represent the first demonstration of the potential the combined use of measures of RS and signal complexity represent in further understanding the cerebral underpinnings of visual perception and learning.