Successful episodic recollection occurs when an event properly binds with its context. Source misattribution demonstrates incorrect binding of a memory with its contextual information. By contrast, false memories are memories of events that did not occur. Although theoretically they should not be bound with contextual information, often, false memories are accompanied by contextual information. This phenomenon is known as content borrowing. This thesis project examined the differences between the two contextual memory errors. The DRM paradigm was used to induce both source misattributions and content borrowing. This allowed the neural differences between the two to be directly tested. No differences were found between source misattribution and content borrowing. However, false memories with content borrowing showed different neural activations from true memory with correct source, true memory with incorrect source, and correct rejection. This suggests that false memories and source misattributions may represent similar errors in memory that rely on gist memory traces. / Master of Science

<p>Women outperform men in face recognition and are especially good at recognizing other females’ faces. This may be caused by a larger female interest in faces. The aims of this study were to investigate if women were more interested in female faces and if depth of friendship was related to face recognition. Forty-one women and 16 men completed two face recognition tasks: one in which the faces shown earlier had been presented one at a time, and one where they had been shown two and two. The Network of Relationships Inventory was used to assess depth of friendships. As hypothesized, but not statistically significant, women tended to recognize more female faces when faces were presented two and two. No relationships were found between depth of friendships and face recognition. The results gave some support for the previously untested hypothesis that interest has importance in women’s recognition of female faces.</p>

There is a long history of research on the effects of reward motivation on memory, but there are still questions concerning how such motivational variables affect memory. In a study that examined the influence of reward anticipation on episodic memory, Adcock, Thangavel, Whitfield-Gabireli, Knutson, and Gabrieli (2006) found that memory was better for scenes preceded by high value reward cues than low value cues (see also Cushman, 2012; Spaniol, Schain, & Bowen, 2013). More recently, Castel, Murayama, Friedman, McGillivray, & Link (2013) observed that anticipation of reward influences selective attention to “to be remembered” (TBR) words and the memories that are formed in both younger (YA) and older adults (OA). Finally, in an examination of reward-motivated memory for both word items and pairs, Mutter, Luttrell, & Steen (2013) found that high reward enhanced associative memory for word pairs for both YA and OA. The theoretical explanation for this finding attributed word pair stimuli as promoting and high reward motivation as selectively enhancing relational encoding strategies for both OA and YA, producing reward effects for associative recognition performance only. The present study conceptually replicated the methodology from Mutter, Luttrell, and Steen (2013) in an examination of how reward motivation at study affects non-verbal single item recognition and dual item recognition for picture pair stimuli. It was expected that high reward will induce both YA and OA to engage in more extensive encoding of TBR information, but that, due to age-related associative deficits (e.g., Naveh – Benjamin, Hussain, Guez, & Bar-On, 2003), the type of encoded representations would differ for the two groups. YA would perform better than OA on the types of recognition that require memory for relational information (i.e., associative and context recognition), but YA and OA would perform equally well on the types of recognition that require memory for item-specific information (i.e., pair and no context recognition). As compared to the word pair stimuli used by Mutter and colleagues (2013), it was expected that picture pair stimuli would alternatively promote item-specific encoding strategies for both OA and YA and high reward would selectively enhance single item recognition performance.

The goal of this work is to create a generator that provides a corpora of input episodes in the specified format, which can be used as an input to test episodic memory models. More specifically, the methods used should ensure the scope to be in years up to a possible lifetime of a typical human agent. It also attempts to verify this on an actual episodic memory model, and test if the generated data has high enough quality to be used for testing psychological paradigms on memory models.

In the present study, we conducted an event-related potentials (ERP) study to examine episodic and semantic memory. We focused on two well-known patterns: the semantic N400 and the old/new fN400. Some researchers have argued that they reflect the same neuropsychological response (Voss & Federmeier, 2011). Others have suggested that they have distinct spatial-temporal signatures and reflect different psychological processes (Bridger, Bader, Kriukova, Unger, & Mecklinger, 2012). In the present study, we analyzed data using the basic N400/fN400 paradigm. We expect to find similar results to Bridger et al. (2012) in that the N400 and fN400 to be reliably different in topography and function.

Thesis advisor: Elizabeth A. Kensinger / Individuals' short- and long-term goals can influence the constructive nature of autobiographical memory recall. The overarching aim of this dissertation was to examine how emotion regulation goals in particular might modulate autobiographical recall at both a behavioral and neural level. In Chapter 1, a new behavioral task instructed individuals to cognitively reappraise the emotions associated with negative and positive events. Results revealed that such emotion regulation goals influence the emotional and other subjective experiences associated with recall, such that up-regulation instructions were linked to greater reported levels of emotional intensity, sensory detail, and recollection (e.g., reliving), and vice-versa for down-regulation instructions. In Chapter 2, functional magnetic resonance imaging (fMRI) was used as participants were instructed to decrease, increase, or maintain the emotions associated with negative autobiographical events. Decreasing emotional intensity primarily engaged neural activity in regions previously implicated in cognitive control (e.g., dorsal and ventral lateral prefrontal cortex), emotion generation and processing (e.g., amygdala, insula), and visual imagery (e.g., precuneus) during an early phase of recall as participants searched for and retrieved events. In contrast, increasing emotional intensity engaged similar regions as individuals prepared to recall negative events (i.e., before a memory cue was presented) and again as they later elaborated upon the details of the events they had recalled. In Chapter 3, individual differences in habitual use of cognitive reappraisal were measured and their relation to neural activity during autobiographical recall was examined. Results revealed that, even when not explicitly instructed to reappraise, habitual use of reappraisal was broadly associated with neural activity in cognitive control regions (e.g., dorsal and ventral lateral prefrontal cortex, dorsal anterior cingulate cortex) as well as emotion processing regions (e.g., amygdala, insula) across memories that varied in their emotionality and specificity. Taken together, these results suggest that short- and long-term emotion regulation goals can influence the construction of autobiographical memories on both behavioral and neural levels. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.

Thesis (Ph.D.)--Boston University / Research in rodents and computational modeling work suggest a critical role for the hippocampus in representing overlapping memories. This thesis tested predictions that the hippocampus is important in humans for remembering overlapping spatial events, and that flexible navigation of spatial routes is supported by key prefrontal and striatal structures operating in conjunction with the hippocampus. The three experiments described in this dissertation used functional magnetic resonance imaging (fMRI) in healthy young people to examine brain activity during context-dependent navigation of virtual maze environments. Experiment 1 tested whether humans recruit the hippocampus and orbitofrontal cortex to successfully retrieve well-learned overlapping spatial routes. Participants navigated familiar virtual maze environments during fMRI scanning. Brain activity for flexible retrieval of overlapping spatial memories was contrasted with activity for retrieval of distinct non-overlapping memories. Results demonstrate the hippocampus is more strongly recruited for planning and retrieval of overlapping routes than non-overlapping routes, and the orbitofrontal cortex is recruited specifically for context-dependent navigational decisions. Experiment 2 examined whether the hippocampus, orbitofrontal cortex, and striatum interact cooperatively to support flexible navigation of overlapping routes. Using a functional connectivity analysis of fMRI data, we compared interactions between these structures during virtual navigation of overlapping and non-overlapping mazes. Results demonstrate the hippocampus interacts with the caudate more strongly for navigating overlapping than non-overlapping routes. Both structures cooperate with the orbitofrontal cortex specifically during context-dependent decision points, suggesting the orbitofrontal cortex mediates translation of contextual information into the flexible selection of behavior. Experiment 3 examined whether the hippocampus and caudate contribute to forming context-dependent memories. fMRI activity for learning new virtual mazes which overlap with familiar routes was compared with activity for learning completely distinct routes. Results demonstrate both the hippocampus and caudate are preferentially recruited for learning mazes which overlap with existing route memories. Furthermore, both areas update their responses to familiar route memories which become context-dependent, suggesting complementary roles in both learning and updating overlapping representations. Together, these studies demonstrate that navigational decisions based on overlapping representations rely on a network incorporating hippocampal function with the evaluation and selection of behavior in the prefrontal cortex and striatum.

The capacity for memory is one of the most profound features of the mammalian brain, and the proper encoding and retrieval of information are the processes that form the basis of learning. The goal of this thesis is to further our understanding of the network-level mechanisms supporting learning and memory in the mammalian brain. The hippocampus has been long recognized to play a central role in learning and memory. Although being one of the most extensively studied structures in the brain, the precise circuit mechanisms underlying its function remain elusive. Principal cells in the hippocampus form complex representations of an animal's environment, but in stark contrast to the interneuron population -- and despite the apparent need for functional segregation -- these cells are largely considered a homogeneous population of coding units. Much work, however, has indicated that principal cells throughout the hippocampus, from the input node of the dentate gyrus to the output node of area CA1, differ developmentally, genetically, anatomically, and functionally. By employing in vivo two-photon calcium imaging in awake, behaving mice, we attempted to characterize the role of dened subpopulations of neurons in memory-related behaviors. In the first part of this thesis, we focus on the dentate gyrus input node of the hippocampus. Chapter 2 compares the functional properties of adult-born and mature granule cells. Chapter 3 expands on this work by comparing granule cells with mossy cells, another glutamatergic but relatively understudied cell type. The second part of this thesis focuses on the hippocampal output node, area CA1. In chapter 4, we characterize an inhibitory microcircuit that differentially targets the sublayers of area CA1. And in chapter 5, we directly compare the contributions of these sublayers to episodic and semantic memory.

Recognizing and understanding where and when events occurred is essential for normal learning and memory of life experiences. Disruptions in the normal processing of spatial and episodic memories can have devastating consequences; in particular, this is one component of the debilitating cognitive deficits of schizophrenia. We are just now beginning to understand the molecular changes in schizophrenia, but still very little is known about how neural circuit are disrupted that lead to behavioral and cognitive dysfunction. In my thesis I will attempt to address two primary questions; how does hippocampal circuitry support spatial-episodic memories, and what goes wrong when these circuits and memories are impaired? First, how precisely do hippocampal circuits support spatial and episodic learning? In 1885 Hermann Ebbinghaus published the first results of a quantitative study of the psychology of memory, showing the predictable forgetting of items over time. Since then, psychologists and cognitive scientists have investigated, described, and defined the precise nature of memory and the behaviors it drives. We eventually realized that memory is not a unitary function of the brain, but that it is dissociable at it’s broadest level into explicit, recollectable memories and the implicit memory of learned skills and abilities. We have now identified networks of brain regions that are essential for these functions. The first functional imaging of the human brain further advanced out understanding of the particular brain regions active during memory tasks and technological advances have allowed us to generate higher resolution functional maps of the brain. Moving to rodent models, we are now getting closer to the memory engram, the set of changes that occur in the brain that store an object, event, or association for future recall. In some particular instances, such as spatial and episodic memories, we already have a very good understanding. But, which particular cells store this information and how does that memory come to be? In my primary thesis project, I will show that the stabilization of firing patterns in principal cells in hippocampal area CA1 supports learning of a spatial reward task. More specifically, as task demands shift pyramidal cells in CA1 specifically encode the reward zone by firing when the mouse is at the correct location. Finally, by modeling the shift of pyramidal cell activity throughout learning, I show the way in which the population of cells shift their firing activity to encode the reward zone. Second, what goes wrong in the normal processing of information that leads to disrupted memory storage and recall? Deficits in spatial and episodic memory are two of the primary cognitive dysfunctions in schizophrenia. While, hallucinations and delusions are perhaps the most widely recognized, they are in part treatable with antipsychotics, while the cognitive and memory deficits are not as well understood, untreatable, and the greatest barrier to rehabilitation. Cognitive deficits observed in schizophrenia patients are, at their core, neuronal circuit disruptions, spanning multiple brain regions and cognitive domains. What can we learn about the circuits underlying these behavioral symptoms? What goes wrong in the brain that is driving these disruptions? I focused on one particular well-characterized brain region (the hippocampus) by recording the activity of hippocampal area CA1 principal cells in an etiologically-validated mouse model of schizophrenia while the mice are actively engaged in a spatial learning task. I identified specific features of the place cell population that are disrupted and predict behavioral deficits - the day-to-day firing stability of the neuronal population and the lack of over-representation of the reward zone. Overall, my work used head-fixed two-photon functional imaging of awake mice to chronically record the activity of distinct components of the hippocampal memory system: long-range inhibitory projections from the entorhinal cortex to hippocampal area CA1, adult-born granule cells in the dentate gyrus, and large heterogeneous populations of CA1 principal cells. I recorded activity during hippocampal-dependent learning and memory tasks in both schizophrenia-mutant and wildtype mice in order to directly probe hippocampal circuits involved in spatial learning. These experiments provided new evidence of the underlying cellular substrates of both healthy and diseased spatial memory processing.

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.