While episodic and spatial memory both depend on the hippocampus, opposite gender differences in these functions suggest they are partly separate, with different neural underpinnings. The anterior and posterior hippocampus differ  in structure and whole-brain connectivity, and studies point to the posterior hippocampus being more involved in spatial memory while the anterior hippocampus’ role in episodic memory is less clear. This thesis aims to explore the role of the anterior and posterior hippocampus, and associated brain regions, in episodic and spatial memory. Paper I studied gender differences in hippocampal activation underlying differences in spatial memory performance. Better performance in men was accompanied by greater right-lateralization of hippocampal activation compared to women. Paper II investigated regions of gray matter that covaried in volume with the anterior and posterior hippocampus, and whether these covariance patterns depended on gender and were related to behavior. The anterior and posterior hippocampus showed different patterns of covariance, with the anterior hippocampus covariance pattern observed in women and the posterior hippocampus covariance pattern primarily in men. Paper III considered whether the location of hippocampal recruitment in episodic memory depends on memory content. Verbal stimuli were associated with more anterior, and left-lateralized, encoding activations than pictorial stimuli, which in turn were associated with more posterior and bilateral encoding activations. This was not observed during retrieval. Paper IV investigated whether resting-state connectivity associated with the anterior and posterior hippocampus predicts episodic and spatial memory performance, respectively. Resting-state connectivity associated with the anterior, not posterior, hippocampus predicted episodic memory performance, while resting-state connectivity associated with the posterior, not anterior, hippocampus predicted spatial memory performance. This thesis lends further support to differences in function and structure between the anterior and posterior hippocampus suggesting that these two sub–segments play different roles in episodic and spatial memory. Further, it suggests that gender differences in anterior and posterior hippocampus function underlies gender differences in episodic and spatial memory, respectively. Considering the anterior and posterior hippocampus, as well as men and women, separately, is hence important when studying the effect of age and pathology on the hippocampus and associated memory functions.

Successful recognition memory decisions depend on mnemonic and decision making processes that are computed by multiple, distributed brain areas. However, little is known about what computations these areas perform or how these areas are connected. Here, I collected behavioral and functional magnetic resonance imaging data from humans during the performance of an old-new recognition memory task with retrospective confidence judgments. Across runs, choice bias was successfully manipulated by providing rewards for correct responses that were either symmetric (equal reward for hits and correct rejections) or asymmetric (one response worth more than the other). Successful recognition memory was associated with activation in anterior prefrontal, parahippocampal, posterior cingulate, and parietal cortex. Resting state functional connectivity demonstrated that these brain areas are organized into two distinct networks. The first network includes parahippocampal cortex and angular gyrus. The second network includes lateral prefrontal cortex and intraparietal sulcus. The hippocampal-cortical network was most active during old vs. new decisions, did not differentiate hits from false alarms, and was differentially active during low confidence old and new judgments. In contrast, while the frontoparietal network was robustly activated by hits, it was not activated during either false alarms or low confidence old judgments. Thus, these two distinct networks can be distinguished by their relative connectivity to the medial temporal lobe vs. lateral prefrontal cortex and their responses during uncertain old judgments and errors. The choice bias manipulation had opposing effects on the parietal components of these networks, which further suggests these networks make distinct contributions to mnemonic decision making. / Psychology

Dual-process models propose that two processes support recognition memory; familiarity, a general sense that something has been previously encountered; and recollection, the retrieval of details concerning the context in which a previous encounter occurred. Event-related potential (ERP) studies of recognition memory have identified a set of old/new effects that are thought to reflect these processes: the 300-500ms bilateral-frontal effect, thought to reflect familiarity and the 500-800ms left-parietal effect, thought to reflect recollection. Whilst the exact functional role of these effects remains unclear, they are widely viewed as reliable indices of retrieval. The ERP literature reviewed in this thesis suggests that the characteristics of these recognition effects vary with task specific details and individual participant differences, suggesting that the recognition effects purported to index retrieval may be conditional on both task and participant. This thesis examined the influence of individual differences on behavioural measures of recognition and the neural correlates of recognition memory, focusing on factors of stimulus material, task performance and participant genotype. Clear evidence of stimulus differences were found, with pictures eliciting more anteriorly distributed effects than words, and a late onsetting frontopolar old/new effect that was unique for voices. Furthermore, the pattern of ERP activity associated with successful recognition of faces appeared to vary as a function of general face recognition ability, with participants poorer at remembering faces exhibiting a 300-500ms old/new effect not present for those good at remembering faces. The data also suggested that activity over right-frontal electrodes, evident in some previous studies, may be participant specific and could reflect additional retrieval support processes. Contrary to expectations, behavioural task performance was not found to significantly modulate the ‘typical’ recognition memory effects. However, a number of genetic polymorphisms were found to significantly influence both behavioural scores and the pattern of ERP activity associated with recognition memory. These results therefore suggest that inherent participant differences influence the neural correlates of recognition memory, in a way that variations in task performance do not. Overall, the results from this thesis therefore suggest that the ‘typical’ bilateral-frontal and left-parietal effects thought to index retrieval are not universal. Furthermore the results suggest that the specific processes engaged during retrieval (as indexed by variations in ERP activity) may be dependent on specific task requirements, stimulus material and the genetic makeup of the individual.

No description available.

This thesis presents research designed to explore the role of physiological and psychological factors in mediating the effects of victimisation upon eyewitness memory. A tripartite model of arousal and memory is proposed encompassing physiological, psychological and motivational mechanisms. In order to investigate the potential role of these mechanisms, three laboratory based studies and one archival study are presented. The results of the laboratory studies suggest that physiological arousal may not influence eyewitness memory. In contrast, whilst direct support for an influence of psychological arousal is not provided, the possibility that psychological arousal may be an important factor cannot readily be dismissed. From a methodological perspective, contrary to existing laboratory-based research concerning visually-induced arousal, the results of the laboratory studies suggest that personal involvement may be an important factor influencing memory. Furthermore, the third laboratory study found that, differences in memory for emotional and neutral material may be a function of inherent differences between the material rather than an influence of arousal. Finally, in order to compare and contrast laboratory based research with the performance of real witnesses, a field based study utilising closed-circuit television to assess eyewitness accuracy for action details was conducted. In line with Studies One and Two, victims and bystanders were not found to differ in their memory performance. This study provides direct support for existing field and archival research suggesting that real victims and bystanders tend to be highly accurate in their eyewitness accounts. Taken together, the results of the research presented in this thesis suggest that whilst physiological arousal may not be an important factor influencing eyewitness memory, psychological and motivational influences may be important when witnesses are personally involved with the target incident.

Introdução: O aprendizado intencional/incidental pode influenciar a memória. A persistência deste efeito avaliado ao longo do tempo foi pouco estudada até o momento. Objetivos: Avaliar a persistência da memória comparando as aprendizagens intencional e incidental. Métodos: A amostra (120 sujeitos funcionalmente independentes, com idade variando de 18 a 81 anos), foi subdividida em dois grupos (experimental - condição ‘intenção de aprender’ - e controle). Uma abordagem ecológica foi utilizada para a avaliação do aprendizado incidental. As avaliações foram realizadas dois e sete dias após a codificação. Resultados: A intenção de aprender e a aquisição incidental (a partir de experiências de vida diária) melhoraram a recuperação da memória no dia dois, mas não sete dias após a codificação. Conclusão: Estes achados sugerem que o estado motivacional (espontâneo ou induzido) que modula o sistema da atenção deve ser importante para a melhora na recuperação das informações aprendidas. / Background: The intentional/incidental learning can influence memory. The persistence of this effect assessed over time has been little studied up to date. Objectives: To evaluate the persistence of memory comparing intentional and incidental learning conditions. Method: The sample (120 functionally independent subjects, age ranging from 18 to 81 years old), was subdivided into two groups (experimental - intention to learn condition - and control). An ecological approach was applied for the incidental learning condition. The assessments were performed two and seven days after the encoding. Results: The intention to learn and the incidental acquisition (from daily life experiences) improved performance two but not seven days after the encoding. Conclusions: These findings suggest that motivational state (spontaneous or induced) which module the system of attention may be important for the improvement in the retrieval of the information learned.

Introdução: O aprendizado intencional/incidental pode influenciar a memória. A persistência deste efeito avaliado ao longo do tempo foi pouco estudada até o momento. Objetivos: Avaliar a persistência da memória comparando as aprendizagens intencional e incidental. Métodos: A amostra (120 sujeitos funcionalmente independentes, com idade variando de 18 a 81 anos), foi subdividida em dois grupos (experimental - condição ‘intenção de aprender’ - e controle). Uma abordagem ecológica foi utilizada para a avaliação do aprendizado incidental. As avaliações foram realizadas dois e sete dias após a codificação. Resultados: A intenção de aprender e a aquisição incidental (a partir de experiências de vida diária) melhoraram a recuperação da memória no dia dois, mas não sete dias após a codificação. Conclusão: Estes achados sugerem que o estado motivacional (espontâneo ou induzido) que modula o sistema da atenção deve ser importante para a melhora na recuperação das informações aprendidas. / Background: The intentional/incidental learning can influence memory. The persistence of this effect assessed over time has been little studied up to date. Objectives: To evaluate the persistence of memory comparing intentional and incidental learning conditions. Method: The sample (120 functionally independent subjects, age ranging from 18 to 81 years old), was subdivided into two groups (experimental - intention to learn condition - and control). An ecological approach was applied for the incidental learning condition. The assessments were performed two and seven days after the encoding. Results: The intention to learn and the incidental acquisition (from daily life experiences) improved performance two but not seven days after the encoding. Conclusions: These findings suggest that motivational state (spontaneous or induced) which module the system of attention may be important for the improvement in the retrieval of the information learned.

O lobo temporal mesial (LTM) é essencial para tarefas de memória e possui muitas conexões com diferentes áreas do cérebro. Pacientes com epilepsia do LTM, refratários ao tratamento medicamentoso, são candidatos à cirurgia para remoção do foco das crises. Portanto, antes da cirurgia, é essencial avaliar eventuais riscos de declínio das funções de memória, por meio de uma série de testes clínicos. Recentemente, abriu-se a possibilidade de estudar certos aspectos do funcionamento cerebral, de modo não invasivo, utilizando Imagens funcionais por Ressonância Magnética (fMRI). O objetivo deste trabalho foi desenvolver métodos que possibilitem a aplicação de protocolos de memória em estudos de fMRI, com vistas a pacientes com epilepsia. Para a manutenção da atenção durante os estudos de fMRI foi confeccionado um dispositivo infravermelho para registrar as respostas obtidas. Além disso, foi desenvolvido um programa (VOI Analyser) para a otimização das análises dos exames de fMRI. Tanto o dispositivo infravermelho como o programa foram amplamente utilizados em vários projetos de pesquisa permitindo o estudo de tarefas complexas. Neste estudo, a tarefa visava identificar as redes funcionais que participam do processo de codificação e recuperação de memória episódica utilizando tarefas visuais de identificação de cenas complexas. Foram estudados nesse estudo 12 voluntários assintomáticos e 7 pacientes com epilepsia do LTM. O estudo de grupo evidenciou o envolvimento de estruturas do LTM. A tarefa demonstrou ter um nível de dificuldade alta, em especial para pacientes, baseando-se na avaliação do tempo de resposta e nível de acertos. Além do estudo dos grupos, foi realizada uma análise por região de interesse (ROI), com ênfase no complexo amídala-hipocampo. Em seguida, o foco do estudo foi voltado para a assimetria hemisférica funcional, por meio do cálculo do índice de lateralização (IL). Além de rever os resultados obtidos pelo IL convencional, resultados preliminares levaram à proposta de um segundo índice corrigido, considerando a quantidade de voxels e a assimetria das ROI. A utilização do índice corrigido tornou a análise mais estável por diminuir a dependência do limiar estatístico considerado. A seguir, foi realizada uma subdivisão do hipocampo em porção anterior, central e posterior a qual indicou uma maior participação da região posterior na tarefa de codificação e da anterior na tarefa de recuperação, tanto entre os voluntários como em pacientes. / Medial temporal lobe (MTL) is essential for memory tasks and has many connections with different areas of the brain. Patients with MTL epilepsy refractory to medical treatment are candidates for surgery to remove the epileptiform tissue. Therefore, before surgery, it is essential to assess the risk of memory function decrease caused by the procedure, through a series of clinical trials. Recently, there is the possibility of studying certain aspects of brain functioning by using a non-invasive technique: functional Magnetic Resonance Imaging (fMRI). The aim of this work was to implement memory protocols in fMRI studies of epilepsy patients. For attention maintenance during the fMRI study an infrared device was built, in order to record the response times. In addition, a software was developed (VOI Analyser) to optimize the analysis of the fMRI examinations. Both have been widely used in several research projects enabling the study of complex tasks. In this study, the task was intended to identify the functional networks involved in the process of encoding and retrieving of episodic memory using a visual task involving complex scenes. 19 subjects were studied: 12 controls and 7 patients with refractory epilepsy. Group study showed the involvement of structures in MTL. The task has demonstrated a high level of difficulty, especially for patients, based on the analysis of response times and correct hits. In addition to the study of groups, an individual analysis was performed by region of interest (ROI), with emphasis on amigdala-hippocampus complex. Then, functional hemispheric asymmetry was studied, by means of the lateralization index (LI). In addition to the computation of conventional LI, an alternative LI was proposed, which considers voxels occupancy and ROI asymmetry. The use of such modified index tuned the analysis more stable by decreasing the dependence on considered statistical threshold. Moreover, LI was also computed on 3 portions of the hippocampus: anterior, middle and posterior. The results indicated a greater involvement of the posterior portion on the encoding task and anterior one in the recovery task, both for volunteers and patients.

There is a body of research on the effect of physical activity oncognition in the old adult population. Less research areconducted on adolescents. The aim for this study is to find out ifadolescents long-term memory is affected by physical activity.144 pupils were asked to rate their physical activity each week.Thereafter their long- term memory was tested through tests onepisodic- and semantic memory. The results showed that thosewho are physically active more than 4 hours had a better scoreon part of the semantic test but no effect was found in theepisodic test. This result indicates that physical activity not onlyaffects working memory, as was shown by previous research butalso has an effect in parts of the semantic long-term memory.

Perceived social discrimination, a salient chronic psychosocial stressor, has an adverse effect on physical and mental health. Cumulative stress compromises adaptive physiologic processes and triggers changes in hypothalamic-pituitary-adrenocortical (HPA) axis functioning. The hippocampus is critical for episodic memory and mediates the HPA stress response. Animal models have demonstrated increased vulnerability of the hippocampus to stress-induced morphological alterations and dysfunction. Previous research has shown that greater psychosocial stress is related to poorer episodic memory performance in older adults. Diffusion-weighted imaging (DWI) studies strongly support the role of the uncinate fasciculus (UF) in episodic memory. Furthermore, psychosocial stress has been associated with white matter (WM) microstructural abnormalities in the UF. Although the effect of chronic psychosocial stress is well established, the effects of social discrimination on WM integrity and episodic memory are not well understood. In this study, we tested the hypothesis that greater perceived social discrimination in older adults is associated with poorer episodic memory performance and structural abnormalities of the UF tract. Twenty-eight participants (63.8 – 73 years, 57.1% female, 42.9% African American) reported experiences of discrimination (EoD) and perceived stress (PSS) and were assessed for episodic memory. High angular resolution diffusion imaging (HARDI) scans were analyzed with probabilistic tractography to examine associations of UF diffusion metrics with EoD scores and episodic memory performance. Spearman’s rank correlation determined a significant positive association between EoD and PSS scores (rs(28) = 0.45, p = 0.017), suggesting perceived discrimination is a chronic stressor and may be a social determinant of health. However, contrary to our expectations, neither EoD nor PSS were significantly related to episodic memory performance and UF diffusion metrics. Future longitudinal research to examine associations between perceived discrimination, episodic memory and WM microstructure in a large cohort is warranted.