Comparative research on event memory has typically focused on the binding of spatial and temporal information in memory, but much less is known about how animals remember information about the source of their memories (i.e., whether the event is something they performed themselves or whether they observed it). The purpose of the present study was to examine how rhesus monkeys (n = 8) and 3- to 4- year-old children (n = 20) remember this information along with other relevant event features (object identity, spatial location, temporal properties and contextual features) in working memory. In Experiment 1, rhesus monkeys completed five different delayed matching-to-sample tasks to assess independent encoding of these five event components. In Experiment 2, the monkeys either performed or observed an event and then had to respond to a randomly selected pair of memory tests used in the previous experiment. In Experiment 3, children were presented with the same memory task, but were given a brief demonstration to learn how to perform the task. Both children and monkeys responded to these tests using photos and shapes (for the identity and spatial tests) and icons (for the temporal, agency and context tests). The monkeys demonstrated significantly above-chance performance on the identity, spatial, temporal and agency tasks. The children were above chance on the one component the monkeys had difficulty with (context), but conversely demonstrated difficulty on the temporal memory test. There was evidence of feature integration in both monkeys and children. Specifically, the children were significantly more likely to respond correctly to the second memory test if they had also been correct on the first memory test. Two of five rhesus monkeys also showed this effect, indicating that for these individuals, the features were integrated in working memory. Implications of this research are discussed in relation to self-awareness and episodic memory research in children and nonhuman species.

Memory impairments are common in individuals with temporal lobe epilepsy (TLE). This is understandable given that temporal lobe brain structures involved in TLE play a central role in encoding memories. It is widely accepted that individuals whose seizure focus is in the left temporal lobe (LTLE) tend to have verbal memory impairments, whereas individuals whose seizure focus is in the right temporal lobe (RTLE) tend to have visuospatial memory impairments. However, evidence of functional subdivisions within the left and right temporal lobes in both the animal and human literature suggest that more specific subtypes of memory impairment may exist in TLE based on differences in seizure foci. The aim of this study was to identify more specific subtypes of memory-impairments in patients with intractable TLE using several measures of memory functioning and cluster analysis. Identification of more specific memory subtypes in TLE could have prognostic significance for patients and contribute to our knowledge about the organization of memory systems of the human brain. Four memory subtypes were identified in this sample: 1) patients with mild to moderate figural memory deficits; 2) patients with moderate to severe figural memory deficits, mild facial recognition deficits, and mild attention/concentration deficits; 3) patients with severe figural memory deficits and mild verbal episodic memory deficits; and 4) patients with no episodic or semantic memory deficits. Unexpectedly, the subtypes found did not exhibit the expected pattern of verbal memory impairments with left temporal lobe damage/dysfunction or visuospatial memory impairments with right temporal lobe damage/dysfunction. However, consistent with the literature, there was a trend towards some clusters with better verbal memory having higher left hippocampal volumes; and a trend towards one cluster with facial recognition deficits having lower anterior temporal lobe volumes. Small sample sizes in this study limited the ability to clearly validate many of the cluster differences, particularly differences in brain volumes. Nevertheless, the results of this study support the hypothesis that subtypes of memory impairment do exist in patients with TLE. With larger sample sizes, it is plausible that additional subtypes may be found, or the characteristics of the subtypes found may become clearer.

Several lines of evidence from rapid serial visual presentation, attentional blink, and dual-task interference phenomena propose that human beings have a significant limitation on the short-term consolidation process. Short-term consolidation is transferring early representations to more durable forms of memory. Although previous research has shown that masks presented after targets interrupt the consolidation process of information, there is not enough evidence for the role of attention in consolidation for episodic memory. One electrophysiological and five behavioral experiments were conducted to investigate the effects of attention and stimulus onset asynchrony (SOA) between targets and masks on episodic memory. Masks were presented after targets with varying SOAs. The participants in the divided attention condition but not the ones in the full attention condition performed the attention-demanding secondary task after the presentation of the masks. The results showed that reducing SOA between targets and masks caused an impairment in memory performance for divided attention but not for full attention, providing evidence for the necessity of attention for the short-term consolidation process. Electrophysiological results demonstrated that this impairment did not result from perceptual processes.

This thesis investigates the effect of normal ageing on the strategies adopted during episodic memory retrieval, using a combination of neuropsychological profiling and neuroimaging data measured during performance on a source memory exclusion task. The exclusion task is a type of source memory task where participants distinguish between targets (studied items from one source e.g. female voice), non-targets (studied items from another source e.g. male voice) and new items. Unlike a source memory task where three separate buttons are pressed for each item at test, in the exclusion task one button is pressed for targets and a second for non-target and new items. As this task is more complex than a normal source memory paradigm and also allows participants to perform the task in more than one way, it places high emphasis on the use of strategies to facilitate retrieval and is therefore ideal for investigating strategic retrieval. Previous source memory studies have shown that while older adults are reasonably good at recognising whether items are old or new, they show marked impairments at remembering the source in which items were presented at study. Dual process theories propose that the age-related decline in source memory occurs because recollection becomes impaired with ageing whereas familiarity remains relatively spared. The results reported in this thesis support dual process theory. Experiment 2a showed that, behaviourally, as expected, the young outperformed the elderly. Event-related potentials (ERPs), recorded while a source memory exclusion test was performed, revealed that both young and older adults showed bilateral frontal and left parietal old/new effects, thought to index familiarity and recollection respectively. Importantly, the magnitude of the left parietal effect was significantly reduced in the older adults. The ERP findings also suggested that dual process theories represent an oversimplification of episodic memory decline with age. In Experiment 1a, three temporally and topographically distinct late frontal old/new effects were present in the younger adults: a bilateral anterior frontal effect (450-900ms post stimulus), a right prefrontal effect (900-1300ms) and a right frontal effect (1300-2000ms). Significant positive correlations between the magnitude of these effects and performance on neuropsychological tests of executive functioning in Experiment 1b, revealed that the bilateral anterior frontal effect was related to working memory, strategy use and planning; the right prefrontal effect was related to working memory and planning while the right frontal effect was related to planning. By contrast, the older adults in Experiment 2a only produced the right frontal effect, which correlated with planning across all three time windows in Experiment 2c. Post-retrieval monitoring in older adults therefore appeared to be qualitatively different than their younger counterparts. Performance on the neuropsychological tests in Experiment 2b, revealed that the older adults’ working memory and strategy use was impaired compared to the young, whereas planning was relatively intact, suggesting that age-related differences in post retrieval processing may be due to reduced executive functioning in older adults. Identifying distinct late frontal effects and demonstrating a relationship between these effects and specific executive functions is a novel finding. The presence of a left parietal target greater than non-target difference in the young adults from Experiment 1a and 2a was interpreted as the young reducing recollection of irrelevant non-target information. The modulation did not differ in magnitude for targets and non-targets in the elderly adults from Experiment 2a, suggesting they were less able to reduce activation of goal irrelevant non-target information. The results in the young adults from Experiment 1a also highlight the importance of considering the context of source information on the processes engaged at retrieval. The bilateral frontal effect was significant for the retrieval of the intrinsic context (source information inherent to the studied item), but not the extrinsic context (source information not inherent to the studied item). This finding was interpreted within a unitisation framework, where the intrinsic context became unitised with the item and enhanced familiarity based remembering. The findings also highlight that in order to fully understand post retrieval processing in both young and old adults, focus should move away from examining quantitative differences in the right frontal effect over long time periods and instead identify qualitatively distinct late frontal effects that may reflect the engagement of various executive functions over time.

Episodic memory is processed by the extended hippocampal system, and pathology or injury to individual components of this system can result in deficits in spatial learning and memory (Aggleton & Brown, 1999). Extensive research regarding spatial memory has been carried out on the anterior thalamic nuclei, a component of the extended hippocampal system, but the contribution of the laterodorsal thalamic nuclei, an adjacent structure with similar neural connections, is less clear. The purpose of the present study was to compare the effects of selective anterior thalamic nuclei lesions (AT) with selective laterodorsal thalamic nuclei lesions (LD) in a novel land-based spatial reference memory task. This assessed the use of proximal and distal visual cues on the propensity to use allocentric or egocentric navigation strategies to locate a specific place in space, as well as the temporal evolution of these navigation strategies. AT lesion impairments were observed in the acquisition trials in both proximal and distal cue conditions. LD lesion rats were unimpaired in the acquisition trials in both visual cue conditions. Across the probe trials, lesion effects were not observed when tested for general navigation, egocentric or allocentric strategies, and there was no clear improvement in performance over the four weeks of probe trials. However, performance was consistently poorer for all groups when proximal cues facilitated navigation compared to distal cues. Performance differences related to cue proximity may reflect the influence of motion parallax, the perceived displacement rate of visual cues. The absence of lesion effects across probes were thought to be due to the preferential use of cued navigation, which was reliant on a single salient beacon, and the lack of integration between cued and place navigation, which was reliant on the formation of a spatial representation.

Comparative research on event memory has typically focused on the binding of spatial and temporal information in memory, but much less is known about how animals remember information about the source of their memories (i.e., whether the event is something they performed themselves or whether they observed it). The purpose of the present study was to examine how rhesus monkeys (n = 8) and 3- to 4- year-old children (n = 20) remember this information along with other relevant event features (object identity, spatial location, temporal properties and contextual features) in working memory. In Experiment 1, rhesus monkeys completed five different delayed matching-to-sample tasks to assess independent encoding of these five event components. In Experiment 2, the monkeys either performed or observed an event and then had to respond to a randomly selected pair of memory tests used in the previous experiment. In Experiment 3, children were presented with the same memory task, but were given a brief demonstration to learn how to perform the task. Both children and monkeys responded to these tests using photos and shapes (for the identity and spatial tests) and icons (for the temporal, agency and context tests). The monkeys demonstrated significantly above-chance performance on the identity, spatial, temporal and agency tasks. The children were above chance on the one component the monkeys had difficulty with (context), but conversely demonstrated difficulty on the temporal memory test. There was evidence of feature integration in both monkeys and children. Specifically, the children were significantly more likely to respond correctly to the second memory test if they had also been correct on the first memory test. Two of five rhesus monkeys also showed this effect, indicating that for these individuals, the features were integrated in working memory. Implications of this research are discussed in relation to self-awareness and episodic memory research in children and nonhuman species.

Episodic memory is a key feature in learning. One must remember past events to act upon a present situation. Episodic memory has been reported to be impaired in individuals with schizophrenia. In order to have an intact episodic memory the contextual features (context) must be bound to the content of the event; this mechanism is referred to as contextual binding. It is proposed that binding errors during the encoding process are responsible for episodic memory impairments in schizophrenia. Since the hippocampal formation is considered to be the central element for contextual binding, it is hypothesized that the synaptic disorganization described in this condition results in such a deficit. Moreover, the hippocampus mediates and influences other cognitive processes such as learning and executive functioning. Hence, a contextual binding deficit can have important consequences on cognition, behaviour and emotions. The object of this dissertation was to investigate the neurofunctioning, neuroanatomy and neurofunctional connectivity of the hippocampus while performing a task that utilized contextual binding mechanisms. Since spatial relational processing is part of contextual binding and is rooted in the hippocampal regions, visuospatial navigation, more precisely a wayfinding task, was used as a probe to activate the hippocampus and its associated regions in a group of patients with schizophrenia and matched healthy controls. The following dissertation presents three original research papers contributing to our understanding of the contextual binding and hippocampal deficits in schizophrenia. The first paper investigates the neurofunctioning of the hippocampus with a wayfinding task. The second paper investigates the hippocampal structural abnormality in schizophrenia and how it relates to performance during the wayfinding task. The third paper explores effective connectivity of the hippocampus with other brain regions involved in navigation in schizophrenia with a particular interest in the prefrontal cortex. These three studies demonstrate significant neurofunctional, neuroanatomical, and neurofunctional connectivity deficits in the hippocampus of the patients with schizophrenia compared to a healthy control population. Results of all three papers are further discussed in terms of research and clinical implications.

Recently in robotics, substantial efforts have been invested on critical applications such as military, nursing, and search-and-rescue. These applications are critical in a sense that the robots may directly deal with human lives in life-or-death situations, and they are therefore required to make highly intelligent decisions as rapidly as possible. The intelligence we are looking for in this type of situations is proactiveness: the ability to anticipate as well as improvise. Anticipation here means that the robot can assess the current situation, predict the future consequence of the situation, and execute an action to have desired outcome based on the determined assessment and prediction. On the other hand, improvisation is performed when the consequence of the situation is not fully known. In other words, it is the ability to deal with a novel situation based on knowledge or skill being acquired before. In this presentation, we introduce a biologically inspired computational model of proactive intelligent behavior for robots. Integrating multiple levels of machine learning techniques such as temporal difference learning, instance-based learning, and partially observable Markov decision process, aggregated episodic memories are processed in order to accomplish anticipation as well as improvisation. How this model can be implemented within a software architectural framework and integrated into a physically realized robotic system is also explained. The experimental results using a real robot and high fidelity 3D simulators are then presented in order to help us understand how extended experience of a robot influences its ability to behave proactively.

Aging research on item- and associative-recognition memory has demonstrated that older adults are deficient in forming associations between two unrelated stimuli. Although older adult performance on tests of item-recognition is similar to younger adult performance, older adults perform worse than younger adults on tests of associative memory (Naveh-Benjamin, Hussain, Guez, & Bar-On, 2003). In addition to the idea that younger adult performance on associative-recognition tests is superior to that of older adults, research has shown that reward cues can enhance motivated learning and item memory performance of younger adults. In an fMRI study that examined the influence of reward anticipation on episodic memory formation, Adcock and colleagues (2006) examined memory performance in response to reward cues that preceded single stimuli and found that young adult participants remembered more stimuli associated with high value reward cues than those associated with low value reward cues. The aim of the current study was to examine whether reward cues that precede a stimulus pair might enhance an association between two stimuli and influence younger and older adult performance on tests of item- and associative-recognition. Our study confirms the idea that while older adult memory for individual items is intact, older adult memory for associations is impaired (Naveh-Benjamin et al., 2003). The results supported the idea that younger and older adult item-recognition is better for high versus low reward cues, but the reward cues had no influence on the associative-recognition of either age group. Therefore, the age-related associative deficit was not improved by reward cues that preceded each stimulus pair.

Abstract This study examined memory functioning from a female perspective, with the aim of determining factors that might impact performance and render the accuracy of memory measurement, particularly with advancing age, problematic. Factors investigated, among others, were the role of attention and/or engagement with the memory tasks administered, state affect (i.e., positive and negative arousal) at time of testing, subjective memory appraisal, particularly in the domain of perceived memory self-efficacy (MSE), and the use of hormone replacement therapy (HRT) by older post-menopausal women. Two experimental computer-based tests of episodic memory, Paired Associates (PA) and Serial Recall (SR), were administered to 181 female participants aged 18 to 86 years. The tasks were designed to emphasise components that make episodic memory especially difficult, and minimise the use of strategies that might assist recall. Thus, they varied the requirement for recall as opposed to recognition, the need to form an association between a pair of unrelated words, and the need to discriminate the most recent list from earlier list(s). Other measures used included a demographic survey administered to participants individually in an interview format, and a number of variables examined in this study derived from responses to items contained in this survey. The research battery also included psychometric measures of transient affective states, psychological well-being, alertness, in addition to measures of global cognitive status and metamemory (i.e., subjective memory appraisal). The overall aim was to examine a range of factors that might influence episodic memory performance in cognitively intact healthy women, and thus render the interpretation of age-related changes to memory functioning problematic. For analyses participants were assigned to three groups - young, middle-aged and older. There were 60 young adults aged 18 to 29 years, 60 middle-aged adults aged 49 to 60 years, and 61 older adults aged 61 to 86 years. Each participant was tested individually in a single session lasting approximately 3 ½ hours, with younger participants requiring less time to complete assessments. Order of test administration and instructions were standardised across the entire sample. Inferential statistics included correlation, t-test statistic, and analysis of variance (ANOVA) with Tukey post-hoc comparisons. Hierarchical multiple regression analyses were conducted to determine key correlates of memory performance outcomes. No significant differences between the cohorts were found in mean years of education. However, episodic memory recall differed significantly by age group. As expected, young adults recalled significantly more words in the memory tasks than their older counterparts, and middle-aged adults outperformed adults in the oldest cohort. Moreover, older adults’ performance deficits were more pronounced in the tasks requiring that they make an association between a pair of unrelated words. Across all cases, transient mood states were significantly related to memory scores; however, individuals in the oldest cohort were particularly vulnerable to mood fluctuations. This cohort experienced a significantly greater decline in positive affect and a significant greater increase in negative affect while undergoing memory testing, highlighting their greater vulnerability to stressors inherent in a memory testing situation. Although scores on the measure of attention were near ceiling, indicative of participants’ level of effort, motivation, and engagement with the memory tasks, the measure of attention discriminated between older and younger adults’ results, and was a key predictor of memory performance. Noteworthy is that attention scores significantly contributed to performance variability in younger and older adults but not in middle-aged adults. Across all cases, age, education, and attention were the key contributing factors to variability in memory scores. Although four lifestyle factors: (1) subjective sleep appraisal, (2) body mass index (BMI), (3) physical activity, and (4) caffeine intake were significantly associated with performance in the memory tasks, once the effects of these key variables were removed, lifestyle factor did not uniquely contribute to performance variability. Moreover, no association was found between hormone replacement therapy (HRT) and episodic memory performance across the broader sample. However, in a small subgroup of older women (n = 15, M age = 66 years), long-term users of this treatment, HRT had a significant effect on memory performance and was indicative of better recall on the memory tasks. The effect of subjective memory appraisal, MSE included, on objective performance outcomes was examined. The results showed that memory self-evaluations were not a significant contributing factor to episodic memory performance, confirming that memory self-appraisal is a poor predictor of actual memory performance, and thus does not pose a challenge to the measurement of age-related changes to memory abilities. Although there were commonalities, factors influencing memory performance differed by age cohort. For example, in young adults, positive mood, a perception of sleeping well, subjective health, and attention were significantly related to performance on the memory tasks. However, once the effect of attention was removed in the regression analysis, no other variable was predictive of episodic memory functioning in this cohort. In contrast, the single significant predictor of memory performance in middle-aged individuals was education, and neither attention, nor positive mood, or physical activity had a significant effect on this cohort’s performance. Similarly, having more years of formal education benefited older adults’ episodic memory functioning. However, high scores on global cognitive functioning and on the tasks measuring attention were equally important to episodic memory recall in this age group. In sum, the significant contribution of age to memory variability attested to the utility of the memory measures in detecting age-related changes to episodic memory functioning, which were independent of deficits in attention or level of education. Moreover, the effect of several factors (e.g., transient mood, lifestyle) on memory scores was explained by an effect on attention, and this has clear implication for the proper evaluation of long-term changes to memory functioning. Limitations of the study and suggestion for future research are discussed.