Converging cognitive and neuroimaging evidence reveals that episodic memory and episodic future thinking (EFT) share component processes. Much less is known about the relationship between EFT and working memory (WM) processes. We hypothesized that WM capacity might provide a crucial componential cognitive role during EFT by supporting the translation of information from discrete episodic memories into a novel future event. We tested this hypothesis in two studies. In Study 1, we collected functional magnetic resonance imaging data during a dual-task interference paradigm that varied WM load and processing demands during EFT. Events imagined while actively maintaining bound item-location representations were less vivid than those imagined during low WM load control trials. Measures of functional and effective connectivity indicated that this behavioral effect corresponded with reduced coupling between the dorsomedial prefrontal cortex and right temporoparietal junction. Events imagined while simultaneously manipulating items in WM took longer to construct than events imagined during control trials and were associated with less functional coupling between the right hippocampus and posterior visuospatial regions. In Study 2, participants completed a similar WM dual-task while simultaneously recalling past events or imagining future events during scalp-recorded encephalography (EEG). As in Study 1, future events imagined while maintaining item-location representations were less vivid than control trials. This effect was specific to future events and corresponded to reduced theta reactivity over bilateral temporoparietal sites. Relative to episodic memory, EFT was associated with alpha synchronization over frontal and parietal sites as well as greater theta-gamma phase amplitude coupling in the right dorsolateral prefrontal cortex. In contrast, episodic memory was associated with greater cross-frequency coupling between frontal theta and occipital gamma oscillations. These results provide novel empirical support for previous theoretical accounts suggesting that WM capacity provides the cognitive workspace necessary to temporarily store and recombine details from discrete episodes into a future event representation. / PHD

Leader prototypes are our expectations for attributes a leader should possess, and these prototypes guide our perceptions and judgments of others with regard to leadership. This dissertation uses a connectionist perspective of leadership to investigate differences in perceptions and judgments of male and female leaders, and provides the first empirical test of Hogue and Lord's (2007) model for gender bias in leadership. In Study 1, leader prototypes are investigated as the mediating process through which perceptions of male and female leaders differ. Furthermore, leader and perceiver gender as investigated as contextual and person factors which impact the accessibility of leader prototypes, thus consequently impacting perceptions and judgments of leaders. The use of leader prototypes in remembering a leader's past behaviors reflects the use of a semantic memory system, where the leader behaviors recalled are influenced by our expectations of the leader, rather than whether the leader actually demonstrated those behaviors. Thus, masculine leadership behaviors demonstrated by a female leader may be discounted, and the leader behaviors recalled may be influenced by gender roles. Study 2 investigates an episodic memory intervention to increase the memory accuracy of leader behaviors as a means to reduce biases in judgments of female leaders. Overall, Study 1 results suggest that activation of agentic attributes; specifically tyranny and masculinity are impacted by leader gender, such that the accessibility of those attributes was higher for male leaders. Contrary to predictions, female leaders did not result in greater accessibility of communal attributes in the leader prototype. No impact of perceiver gender was seen on this mediation process. Subsequently, accessibility of these attributes impacts participants' perceptions and judgments of leadership. Study 2 results indicate behavior recognition accuracy of communal behaviors drives participants' negative perceptions and judgments of the female leader. Limitations and directions for future research are discussed. / Ph. D.

Transfer-appropriate processing (TAP) proposes that retrieval success is based on the match between processing at encoding and retrieval. We propose that the processing described by TAP determines the contextual cues that are encoded with an event. At retrieval, the presence or absence of contextual cues matching the encoding cues will influence success. To implement these principles as a strategy to improve memory, the nature of future retrieval processing or cues must be known during encoding. As this is unlikely in real-world memory function, we propose that increased encoding variability – increasing the range of encoded cues – increases the likelihood of TAP when the retrieval scenario is unknown. The larger the set of encoded cues, the more likely those cues will recur during retrieval and therefore achieve TAP. Preliminary research in our lab (Diana, unpublished data) has found that increased encoding variability improves memory for item information in a novel retrieval context. To test whether this benefit to memory is due to the increased likelihood of TAP, the current experiment compared the effects of encoding variability under conditions that emphasize TAP to conditions that reduce TAP. We found main effects of encoding variability and TAP, but no interaction between the two. Planned comparisons between high and low variability encoding contexts within matching and non-matching retrieval contexts did not produce a significant difference between high and low variability when encoding-retrieval processing matched. We conclude that further studies are necessary to determine whether encoding variability has mechanisms that benefit memory beyond TAP. / M.S. / It is well accepted within the episodic memory literature that successful memory retrieval is often driven by context cues. Specifically, the cues that are stored with the memory of the event. To develop a better understanding of how episodic memory works, we must understand how manipulating context cues changes memory performance. One way to investigate the effects of context manipulation is using encoding variability, which refers to the amount of variability (i.e., change) in context cues from one repetition of an item or event, to the next. Preliminary research in our lab (Diana, unpublished data) has found that increased encoding variability improves memory retrieval in a novel context, but it is unclear why this is the case. We proposed that the mental processing described by transfer-appropriate processing (TAP) – a principle stating that memory retrieval success is determined by the match, or overlap, between the mental processing at encoding (i.e., memory formation) and memory retrieval – determines the contextual cues that are stored with the memory at encoding. We hypothesized that encoding variability works even when TAP has already been achieved by matching the processing and cues at encoding to those at retrieval. Alternatively, we hypothesized that encoding variability works by specifically achieving TAP, so that encoding variability is only helpful when the encoding and retrieval contexts do not match. Results indicated partial support for the alternative hypothesis, suggesting that encoding variability works by achieving TAP. However, these results were not sufficiently conclusive, and it is likely that there are other mechanisms that allow for encoding variability to improve memory. This study establishes the groundwork for future work examining encoding variability and its effects on memory.

This thesis aims to explore the two dominant functional roles of the hippocampal formation, in the relational encoding of episodic memory and the neural representation of allocentric space, using a combination of pharmaceutical manipulations and single-unit recording techniques in rodents. The first part of this thesis focuses on episodic-like memory, defined by the original episodic memory triad: ‘what-where-when’ (Tulving 1972), which enables the behavioural aspects of episodic memory to be tested in non-human animals. Permanent neurotoxic lesions of the hippocampus and it’s subregions were induced to assess their role in a putative episodic-like memory task developed by Eacott and Norman (2004). In view of the difficulties encountered in successfully demonstrating the temporal component of episodic-like memory in rats, this task tested integrated memory for ‘what-where-which’, where the temporal component (when) was replaced with another event specifier: context (on ‘which’ occasion). Disruption of the hippocampal circuitry led to a specific impairment in the integration of all three event components, whereas the associative recognition of any combination of these features in isolation was left intact. These results confirm the hippocampal dependence of this episodic-like memory task and further reveals the necessity of both CA3 and CA1, hypothetically due to the underlying autoassociative role of CA3 with CA1 functioning as the vital output pathway for this associated information and/or as a mismatch detector. There has been much debate over the inclusion of the temporal component and sceptics may argue that any such interpretations of task-dependence on episodic-like memory processing are invalid considering the requirement for temporal processing is absent. Due to the proposal that a temporal framework necessarily provides the foundation on which episodic memories are built, the second chapter focuses on the development of a suitable protocol in which integrated memory for the original ‘what-where-when’ episodic memory triad can be reliably tested. The other main function attributed to the hippocampus was brought to light by the fascinating revelation that it’s neurons selectively fire in different regions of an environment, termed ‘place cells’ (O’Keefe and Dostrovsky 1971). From the numerous publications resulting from this discovery it has emerged that place cells not only respond to the spatial features of the environment but are also sensitive to a multitude of non-spatial features. These characteristics support the logical assumption that the primary firing patterns of the hippocampus should underlie it’s main purported roles, leading to speculations that they reflect episodic memory processes. The second part of this thesis aims to examine the relationship between hippocampal cells and behaviour by extending the work of Ainge et al. (2007a), in which a subset of hippocampal place cells were found to encode both current and intended destination in a double Y-maze ‘win-stay’ task. The development of these ‘goal-sensitive’ cells were initially investigated during the learning phase of this task. An exciting pattern of results showed a strong positive correlation between the emergence of goal-sensitive firing and behavioural performance on the task, tempting speculations that these firing patterns may underlie spatial learning and future planning, necessary to support performance. To ensure these firing patterns were not a mere reflection of greater experience on the maze, a second study was conducted in which the task demands changed over set periods of days. A significant increase in the proportion of cells demonstrating goal-sensitive firing was revealed when the protocol shifted to incorporate the spatial memory demands of the ‘win-stay’ task, with all other parameters of the protocol remaining constant. These results support the theory that goal-sensitive firing patterns are specifically related to the learning and memory demands of the spatial task, not a result of increased exploration of the maze. The last of this series of studies assessed hippocampal-dependence of this task and revealed that bilateral hippocampal lesions induced an impairment in spatial ‘win-stay’ performance. Collectively, these experiments demonstrate that goal-sensitive firing of hippocampal cells emerge in line with behavioural performance in a hippocampal-dependent task and the emergence of these firing patterns are specific to the learning and memory demands of a spatial ‘win-stay’ protocol. The functional role of the hippocampus in allocentric spatial processing may thus underpin it’s function in episodic memory and potentially in the imagining and planning of future events, whereby the hippocampus provides a ‘space’ in which retrieved information can be integrated in a coherent context to support the fluent and flexible use of information. This hippocampal function would necessarily require visual information to be accessed, concerning the arrangement of landmarks and cues within the environment, in association with information regarding internal orientation and direction and this leads to the question assessed in the final part of this thesis of where this integration occurs. Based on anatomical evidence and the current literature, the postsubiculum, an input structure to the hippocampus, emerged as a potential site for the convergence of sensory cues into the internally generated head direction cell and place cell networks to enable hippocampal-dependent spatial processing. Thus, the effects of temporary pharmacological blockade of AMPARs and NMDARs in the postsubiculum were assessed on the encoding of spatial memory in an object recognition paradigm. The impairment revealed in the ability to recognise novel object-place configurations demonstrates a key role for NMDAR-dependent plasticity within the postsubiculum itself in the formation of allocentric spatial memory. In summary, the experimental results reported in this thesis further elucidate the critical role the hippocampal formation plays in spatial and episodic memory by combining evidence from cellular physiology and neuroanatomy to the behaving animal and extends these findings to discuss a more general role for the hippocampus in imagining both past and future events, in order to successfully navigate, learn and enable past experience to influence our intended future plans and decisions.

It is well established that older adults show a deficit in episodic memory. The associative deficit hypothesis (ADH) (Naveh-Benjamin, 2000) suggests that an age-related reduced ability to create links between units of information is a major contributor to the episodic deficit. It has been a robust finding that older adults show a disproportionate decline in associative memory relative to item memory when compared to young adults. Previous researchers have investigated the role of the frontal lobes (FL) by studying the effect of reduced attentional resources in the associative deficit. However, they have not found that divided attention in young adults produces the disproportionate associative decline seen in aging and it is thought that some cognitive process other than the allocation of attentional resources may contribute to the associative deficit. The present study intended to use a divided attention (DA) task that also engages medial temporal brain regions (MTL) in order to tax additional parts of the network involved in creating associations and provide indirect support for the role of the MTL in the associative deficit. However, the associative memory deficit in older adults was not replicated due to unique poor associative memory performance of some young adults in the study. Analyses excluding these participants show support for the role of the MTL in the associative deficit. However, the young poor performers may provide support for the role of FL function in the associative deficit and show that poor associative memory may not be limited to the older adult cohort.

Evidence suggests that when memories are reactivated they become labile and can be updated or even erased. Reactivation induces plasticity in memory representations, rendering them fragile, much as they were after initial acquisition. When a memory has been reactivated it must be re-stabilized, which requires reconsolidation. A recent set of studies established the phenomenon of memory reconsolidation for episodic memory (Hupbach et al., 2007, 2008, 2011). That reconsolidation effects apply to explicit memory, which requires conscious recollection, has far reaching implications. In the Hupbach et al. studies the ability of subtle reminders to trigger reconsolidation was investigated; these reminders consisted of the same spatial context, the same experimenter and a reminder question. Given we live in a predictable world, episodes are not random occurrences of events in time and space, but instead consist of statistical and semantic regularities. This leaves open the question of whether semantic relations and statistical regularities between episodes can trigger a reactivation of episodic memory. If so, how would this affect the status of the reactivated memory? This dissertation explored the role of semantic relatedness between the elements of different episodes in memory reactivation and subsequent updating. We focused particularly on categorical and contextual aspects of semantic relations. A series of experiments considered different kinds of semantic relations between elements of episodes, providing evidence of memory reactivation and updating as a consequence of basic level category relations between items in two separate episodes. We also tested the predictions of the Temporal Context Model (TCM) (Sederberg et al., 2011) for our experimental paradigm and show that the current TCM model is not able to account for all the effects of semantic relatedness in the reconsolidation paradigm. Finally, we explore an alternative approach that seeks to explain memory reconsolidation as Bayesian Inference. Our results provide support for this Bayesian framework, showing the potential of it for exploring different aspects of memory organization.

<p>Involuntary episodic memories are memories that come into consciousness without preceding retrieval effort. These memories are commonplace and are relevant to multiple mental disorders. However, they are vastly understudied. We use a novel paradigm to elicit involuntary memories in the laboratory so that we can study their neural basis. In session one, an encoding session, sounds are presented with picture pairs or alone. In session two, in the scanner, sounds-picture pairs and unpaired sounds are reencoded. Immediately following, participants are split into two groups: a voluntary and an involuntary group. Both groups perform a sound localization task in which they hear the sounds and indicate the side from which they are coming. The voluntary group additionally tries to remember the pictures that were paired with the sounds. Looking at neural activity, we find a main effect of condition (paired vs. unpaired sounds) showing similar activity in both groups for voluntary and involuntary memories in regions typically associated with retrieval. There is also a main effect of group (voluntary vs. involuntary) in the dorsolateral prefrontal cortex, a region typically associated with cognitive control. Turning to connectivity similarities and differences between groups again, there is a main effect of condition showing paired > unpaired sounds are associated with a recollection network. In addition, three group differences were found: (1) increased connectivity between the pulvinar nucleus of the thalamus and the recollection network for the voluntary group, (2) a higher association between the voluntary group and a network that includes regions typically found in frontoparietal and cingulo-opercular networks, and (3) shorter path length for about half of the nodes in these networks for the voluntary group. Finally, we use the same paradigm to compare involuntary memories in people with posttraumatic stress disorder (PTSD) to trauma-controls. This study also included the addition of emotional pictures. There were two main findings. (1) A similar pattern of activity was found for paired > unpaired sounds for both groups but this activity was delayed in the PTSD group. (2) A similar pattern of activity was found for high > low emotion stimuli but it occurred early in the PTSD group compared to the control group. Our results suggest that involuntary and voluntary memories share the same neural representation but that voluntary memories are associated with additional cognitive control processes. They also suggest that disorders associated with cognitive deficits, like PTSD, can affect the processing of involuntary memories.</p> / Dissertation

The role of the primate frontopolar cortex (FPC) has been investigated using human neuroimaging, lesion and disruption techniques. The results of these investigations have led to a variety of theories regarding the function of this region. It has been linked to the formation of task sets, the performance of multiple tasks, reasoning, context-specific memory (including episodic memory, prospective memory and source memory), attention to internally or externally generated information, mentalising and decision-making. It has not previously been possible to study this area using animal lesion techniques. Here, behavioural experiments conducted using non-human primates (rhesus macaque monkeys) who have received lesions to the frontal pole investigate the contribution of this region to context-specific memory, decision-making and social cognition. Functional magnetic resonance imaging (fMRI) is used to investigate changes in functional network connectivity which occur after lesions to this region. A long-lasting impairment is observed in contextual memory judgements (specifically, how recently a stimulus was encountered) after lesions to the frontal pole. An analysis of the influence of the outcomes of previous choices on behaviour on an analogue to the Wisconsin Card Sorting Test (WCST) indicate that monkeys with lesions to area 10 may be less influenced by the outcomes of an extended history of rewards than control animals. Long-lasting widespread disruption to functional networks after lesions to this region indicate that indirect anatomical connections from this region to posterior areas play a crucial role in the normal functioning of posterior networks.

The goal of this work is to design a model of episodic memory for virtual agents capable of creating false memories and implement its prototype. The model architecture is inspired by present day knowledge about human episodic memory. Core structures in our model are the chronobags storing details of experienced episodes, and the schemabag storing the general scripts for all experienced events. The episodes are stored in the form of AND-OR trees and it is possible to derive missing details from the stored scripts during recall. We followed the work of Burkert and implemented a prototype of designed memory model in Java using the Pogamut 3 Framework. The model is parameterizable and it is evaluated in several experiments. In these experiments we looked on the trends in correct and incorrect recalls over time and we simulated the experiment demonstrating existence of room schemata. We compared the results produced by our model with the data from psychological researches and we showed that our model can produce false memories similar to false memories recollected by humans.

L’objectif de cette thèse visait à rechercher une explication à l’altération de la mémoire épisodique observée dans les épilepsies partielles pharmaco-résistantes (EPPR). Nous avons inscrit notre contribution explicative dans une double perspective métacognitive et motivationnelle, en émettant l’hypothèse que l’altération mnésique pourrait être due à une altération des processus métacognitifs ou/et à des croyances motivationnelles dysfonctionnelles. Un protocole expérimental, basé sur une tâche de mémorisation de paires de mots, a été utilisé afin de tester l’intégrité des processus métacognitifs en mettant en relation un jugement d’auto-contrôle (jugement d’apprentissage, JOL) et deux mesures d’autorégulation (choix des items et temps alloué à leur apprentissage). L’évaluation de croyances motivationnelles a été effectuée grâce à des questionnaires concourants à la tâche. La présence d’une altération de la mémoire épisodique est confirmée dans l’ensemble des sous-groupes testés [épilepsie du lobe temporal (ELT), d’épilepsie du lobe frontal (ELF) et ELT après chirurgie]. La faible performance mnésique observée chez les sujets souffrant d’épilepsie ne peut pas être expliquée par une altération des jugements d’auto-contrôle (JOL). En effet, les sujets souffrant d’ELT ou d’ELF savent correctement auto-évaluer leur rappel futur. En revanche, l’altération mnésique pourrait s’expliquer par une altération du processus d’auto-régulation, car la stratégie de sélection des paires, observée chez les épileptiques, s’effectue indépendamment de la difficulté objective des paires, des jugements d’auto-contrôle, ou du rappel précédant, contrairement à ce qui est observé chez les sujets sains. Par ailleurs, l’analyse des croyances motivationnelles montre que la valeur du sentiment d’auto-efficacité (SAE) au cours d’une tâche de mémoire est faible chez les épileptiques temporaux qu’ils soient opérés ou non et plus cette estimation est faible plus la performance mnésique est altérée. L’absence de mise en œuvre d’activités d’auto-régulation adaptées pourraient donc être, en partie, due à la présence d’un SAE faible. En effet, ce sentiment joue un rôle médiateur dans l’engagement dans les tâches : si son niveau est bas il est susceptible de produire une diminution des efforts, un manque de persévérance et un abandon de la tâche, et de ce fait d’affecter négativement la performance. Compte tenu de ces résultats, un programme visant à favoriser les performances mnésiques dans l’épilepsie ne devrait pas se centrer prioritairement sur la rééducation des processus métacognitifs mais plutôt sur le renforcement positif du SAE. / This thesis aimed at explaining the impairment of episodic memory observed in partial drug-resistant epilepsies. We intended to determine to what extent these difficulties could be related to metamemory impairment and/or to dysfunctional self-beliefs. We employed an experimental design based on a paired-associated learning task in order to test the integrity of monitoring and control processes. These processes were assessed on the basis of judgment of learning (JOLs), item selection and study-time allocation. Also, motivational self-beliefs (self-efficacy and causal attributions) were assessed by questionnaires based on the memory task. Results revealed a clear deficit of episodic memory in all groups of patients compared with controls [temporal lobe epilepsy (TLE), frontal lobe epilepsy (FLE) and TLE after surgery]. Memory impairment cannot be explained by a deficit in the monitoring process: TLE and FLE patients are able to accurately predict their future recall. By contrast, the deficit of memory might be due to an impairment of control processes: contrary to what we observed among healthy group, item selection strategy used by epileptic patients is not linked to the item objective difficulty, to judgments of learning, nor to the initial recall. Also, in the case of TLE (before and after surgery), the analysis of self-beliefs evidences low self-efficacy estimations during the memory task ; the lower the evaluation, the more impaired is the performance of recall. Thus, the lack of well adapted activities of control may be due to this feeling. Self-efficacy belief can act as a mediator in the carrying out of learning activities: if its level is low, it may well induce a decrease of efforts, a lack of perseverance and the giving up of the task. Given these results a program aiming at improving the memory performance in epilepsy should not be focused in priority on the reeducation of metacognitive processes but rather on a positive reinforcement of self-efficacy beliefs.