Previous research has investigated intentional retrieval of contextual information and contextual influences on object identification and word recognition, yet few studies have systematically investigated context effects in episodic memory for objects. To address this issue, unique objects on a white background or embedded in a visually rich context were presented to participants. At test, the object was presented either in the original or a different context. Chapter 2 demonstrated that a context shift decrement (CSD)--decreased recognition performance when context is changed between encoding and retrieval--was observed. In four studies with young adults, the CSD was not attenuated by encoding or retrieval manipulations. Chapter 3 revealed that the CSD was resistant to aging and neuropsychological status. Importantly, older adults classified as high MTL performed better on the recognition task than those classified as low MTL, and as well as young adults, supporting the successful aging hypothesis. Chapter 4 focused on elucidating the neural correlates of the CSD using functional Magnetic Resonance Imaging. Right PHG activation during encoding was associated with subsequent recognition of objects in the context change condition. This same region was activated during recognition, suggesting it may automatically reinstate visual contextual information. Overall, the CSD is attributed to the automatic and obligatory binding of object and context information in episodic memory that results in an integrated representation, mediated by the hippocampal complex.

Thesis advisor: Scott D. Slotnick / Episodic memory is a constructive process in which a system of sensory and control processes works to transport one’s conscious mind through time–in essence, recreating a previous perceptual experience. For instance, sensory-specific activity that was associated with an original encoding experience is reinstated during retrieval–almost as if the sensory regions are processing the stimulus again, albeit this activation is smaller in spatial extent. This process of sensory-specific reinstatement occurs across all sensory modalities (e.g., Gottfried et al., 2004; Nyberg et al., 2001; Vaidya et al., 2002; Wheeler et al., 2000). That is, retrieval of a visually encoded stimulus (e.g., a picture of a dog) reinstates activity in the visual cortex, while retrieval of an aurally encoded stimulus (e.g., a barking dog) reinstates activity in the auditory cortex. In Chapter 1 and Chapter 2, I demonstrate the specificity of such sensory reinstatement during true memory for visual features and investigate the role of such sensory regions during the construction of false memory for visual features. In addition to sensory processes, our conscious experience of memory also relies on control regions. At the center of this memory control network sits a key memory structure, the hippocampus, as well as other important control regions such as the dorsolateral prefrontal cortex and the parietal cortex. Furthermore, the parahippocampal cortex appears to play a critical role in memory; however, the exact role of this region has been debated (Aminoff, Kverga, & Bar, 2013). In Chapter 3, I investigate the functional role of the parahippocampal cortex during true memory and false memory, and provide evidence that the parahippocampal cortex mediates general contextual processing.

No description available.

Déficits cognitivos e alterações cerebrais estruturais são comumente encontrados em idosos deprimidos. Este estudo teve como objetivos comparar o volume de regiões de interesse, hipocampo e giro para-hipocampal, de idosos com transtornos depressivos e sem transtornos depressivos utilizando a técnica de morfometria baseada no voxel, investigando se há correlação entre o volume dessas regiões e os escores dos testes cognitivos. Neste estudo, as diferenças clínicas, demográficas e de volume de substância cerebral total foram avaliadas por meio de exames de ressonância magnética estrutural em 48 idosos com transtornos depressivos e 31 controles. Os dados contínuos dos grupos de indivíduos foram comparados pelo teste t de Student ou pelo teste de Mann-Whitney, e a análise das freqüências de categorias foi feita utilizando-se o teste exato de Fisher ou o teste do qui quadrado com correção de continuidade. A comparação dos escores nos testes cognitivos dos dois grupos foi feita por meio da análise de covariância, pois os grupos eram diferentes quanto à escolaridade. A correlação entre o volume de cada estrutura e os escores nos testes cognitivos, para cada grupo estudado, foi feita utilizando-se o programa \"Statistical Parametric Mapping\" e o coeficiente de correlação de Pearson. Pacientes e controles eram similares quanto ao volume cerebral total e quanto às regiões de interesse, mas os pacientes apresentaram desempenho inferior em testes de avaliação da memória, das funções executivas e da velocidade de processamento. No grupo de idosos com transtornos depressivos, foi verificada correlação entre teste de memória episódica verbal e volume do hipocampo esquerdo (p = 0,023) e giro para-hipocampal direito (p = 0,044) e esquerdo (p = 0,007). Nesse grupo, também foi verificada correlação entre giro para-hipocampal esquerdo, teste de memória episódica visual (p = 0,039) e evocação tardia em teste de aprendizagem visuo-verbal (p = 0,040). No grupo de idosos sem transtornos depressivos, foi observada correlação entre desempenho no teste Mini-exame do Estado Mental e hipocampo direito (p = 0,010), e total de evocação em teste de aprendizagem visuo-verbal e giro para-hipocampal direito (p = 0,10) e esquerdo (p = 0,015). Este estudo contou com algumas limitações, como: grupos heterogêneos quanto à escolaridade; pacientes deprimidos, em sua maioria, com sintomas leves e moderados; falta de dados referentes ao tempo total de doença dos pacientes com história de episódios depressivos prévios ou quadros de depressão crônica; e o fato de a maioria dos idosos do grupo controle já ter participado de grupos para a terceira idade. Os resultados corroboraram que idosos deprimidos apresentam alterações de memória, e que essas alterações se correlacionam com alterações estruturais, dado que pode auxiliar a compreensão da fisiopatologia da depressão em idosos. / Cognitive deficits and structural brain alterations are usually found in depressed elderly. The objective of this study was to compare the volume of the regions of interest, hippocampus and parahippocampal gyrus, of elderly with and without depressive disorders using the voxel-based morphometry technique, investigating whether there is a correlation between the volume of these regions and the scores on these cognitive tests. In this study, the clinical and demographic differences, as well as the difference in the volume of the total brain matter were assessed using structural magnetic resonance imaging in 48 elderly people with depressive disorders and 31 controls. The continuous data of the groups of subjects were compared using the Student\'s t test or the Mann-Whitney test; and the analysis of category frequency was performed using the Fisher\'s Exact Test or the Chi-square test with Continuity Correction. The comparison of the scores on the cognitive tests of both groups was carried out using the Analysis of Covariance, since the groups were different in terms of level of education. The correlation between the volume of each structure and the scores on the cognitive tests for each group studied was made using the Statistical Parametric Mapping program and Pearson\'s Correlation Coefficient. Patients and controls were similar regarding the total brain volume and also with respect to the regions of interest; however, the patients presented lower performance on the tests that assessed memory, executive functions and processing speed. In the group of elderly subjects with depressive disorder, there was a correlation between the verbal episodic memory test and the volume of the left hippocampus (p = 0.023); right (p = 0.044) and left (p = 0.007) parahippocampal gyrus. In this group, there was also a correlation between the left parahippocampal gyrus, the visual episodic memory (p = 0.039) and the delayed naming in the visual-verbal learning test (p = 0.040). In the group of elderly without depressive disorders, there was a correlation between the performance on the Mini Mental State Examination and the right hippocampus (p = 0.010), and the total naming on the visual-verbal learning test and the right (p = 0.10) and left (p = 0.015) parahippocampal gyrus. This study had some limitations such as groups with different levels of education, most depressed patients had mild to moderate symptoms, lack of data regarding the total length of the disease in patients with previous history of depressive episodes or chronic depression, and most elderly of the control group had participated in elderly support groups. The results demonstrate that the elderly with depressive disorders have memory deficits and that these deficits are correlated to structural brain alterations. Such finding might help to understand the pathophysiology of depression in the elderly.

Déficits cognitivos e alterações cerebrais estruturais são comumente encontrados em idosos deprimidos. Este estudo teve como objetivos comparar o volume de regiões de interesse, hipocampo e giro para-hipocampal, de idosos com transtornos depressivos e sem transtornos depressivos utilizando a técnica de morfometria baseada no voxel, investigando se há correlação entre o volume dessas regiões e os escores dos testes cognitivos. Neste estudo, as diferenças clínicas, demográficas e de volume de substância cerebral total foram avaliadas por meio de exames de ressonância magnética estrutural em 48 idosos com transtornos depressivos e 31 controles. Os dados contínuos dos grupos de indivíduos foram comparados pelo teste t de Student ou pelo teste de Mann-Whitney, e a análise das freqüências de categorias foi feita utilizando-se o teste exato de Fisher ou o teste do qui quadrado com correção de continuidade. A comparação dos escores nos testes cognitivos dos dois grupos foi feita por meio da análise de covariância, pois os grupos eram diferentes quanto à escolaridade. A correlação entre o volume de cada estrutura e os escores nos testes cognitivos, para cada grupo estudado, foi feita utilizando-se o programa \"Statistical Parametric Mapping\" e o coeficiente de correlação de Pearson. Pacientes e controles eram similares quanto ao volume cerebral total e quanto às regiões de interesse, mas os pacientes apresentaram desempenho inferior em testes de avaliação da memória, das funções executivas e da velocidade de processamento. No grupo de idosos com transtornos depressivos, foi verificada correlação entre teste de memória episódica verbal e volume do hipocampo esquerdo (p = 0,023) e giro para-hipocampal direito (p = 0,044) e esquerdo (p = 0,007). Nesse grupo, também foi verificada correlação entre giro para-hipocampal esquerdo, teste de memória episódica visual (p = 0,039) e evocação tardia em teste de aprendizagem visuo-verbal (p = 0,040). No grupo de idosos sem transtornos depressivos, foi observada correlação entre desempenho no teste Mini-exame do Estado Mental e hipocampo direito (p = 0,010), e total de evocação em teste de aprendizagem visuo-verbal e giro para-hipocampal direito (p = 0,10) e esquerdo (p = 0,015). Este estudo contou com algumas limitações, como: grupos heterogêneos quanto à escolaridade; pacientes deprimidos, em sua maioria, com sintomas leves e moderados; falta de dados referentes ao tempo total de doença dos pacientes com história de episódios depressivos prévios ou quadros de depressão crônica; e o fato de a maioria dos idosos do grupo controle já ter participado de grupos para a terceira idade. Os resultados corroboraram que idosos deprimidos apresentam alterações de memória, e que essas alterações se correlacionam com alterações estruturais, dado que pode auxiliar a compreensão da fisiopatologia da depressão em idosos. / Cognitive deficits and structural brain alterations are usually found in depressed elderly. The objective of this study was to compare the volume of the regions of interest, hippocampus and parahippocampal gyrus, of elderly with and without depressive disorders using the voxel-based morphometry technique, investigating whether there is a correlation between the volume of these regions and the scores on these cognitive tests. In this study, the clinical and demographic differences, as well as the difference in the volume of the total brain matter were assessed using structural magnetic resonance imaging in 48 elderly people with depressive disorders and 31 controls. The continuous data of the groups of subjects were compared using the Student\'s t test or the Mann-Whitney test; and the analysis of category frequency was performed using the Fisher\'s Exact Test or the Chi-square test with Continuity Correction. The comparison of the scores on the cognitive tests of both groups was carried out using the Analysis of Covariance, since the groups were different in terms of level of education. The correlation between the volume of each structure and the scores on the cognitive tests for each group studied was made using the Statistical Parametric Mapping program and Pearson\'s Correlation Coefficient. Patients and controls were similar regarding the total brain volume and also with respect to the regions of interest; however, the patients presented lower performance on the tests that assessed memory, executive functions and processing speed. In the group of elderly subjects with depressive disorder, there was a correlation between the verbal episodic memory test and the volume of the left hippocampus (p = 0.023); right (p = 0.044) and left (p = 0.007) parahippocampal gyrus. In this group, there was also a correlation between the left parahippocampal gyrus, the visual episodic memory (p = 0.039) and the delayed naming in the visual-verbal learning test (p = 0.040). In the group of elderly without depressive disorders, there was a correlation between the performance on the Mini Mental State Examination and the right hippocampus (p = 0.010), and the total naming on the visual-verbal learning test and the right (p = 0.10) and left (p = 0.015) parahippocampal gyrus. This study had some limitations such as groups with different levels of education, most depressed patients had mild to moderate symptoms, lack of data regarding the total length of the disease in patients with previous history of depressive episodes or chronic depression, and most elderly of the control group had participated in elderly support groups. The results demonstrate that the elderly with depressive disorders have memory deficits and that these deficits are correlated to structural brain alterations. Such finding might help to understand the pathophysiology of depression in the elderly.

Synchronized oscillations of ensembles of neurons in the brain underlie human cognition and behaviors. Neuronal network oscillations can be described by the physics of coupled dynamical systems. This dissertation examines the dynamic network activities in two distinct neurocognitive networks, the salience network (SN) and the ventral temporal cortex-dorsolateral prefrontal cortex (VTC-DLPFC) network, during perceptual decision-making (PDM). The key nodes of the SN include the right anterior insula (rAI), left anterior insula (lAI), and dorsal anterior cingulate cortex (dACC) in the brain. When and how a sensory signal enters and organizes within the SN before reaching the central executive network including the prefrontal cortex has been a mystery. Second, prior studies also report that perception of visual objects (face and house) involves a network of the VTC—the fusiform face area (FFA) and para-hippocampal place area (PPA)—and the DLPFC. How sensory information enters and organizes within the VTC-DLPFC network is not well understood, in milliseconds time-scale of human’s perception and decision-making. We used clear and noisy face/house image categorization tasks and scalp electroencephalography (EEG) recordings to study the dynamics of these networks. We demonstrated that beta (13–30 Hz) oscillation bound the SN, became most active around 100 ms after the stimulus onset, the rAI acted as a main outflow hub within the SN, and the SN activities were negatively correlated with the difficult tasks. We also uncovered that the VTC-DLPFC network activities were mediated by beta (13-30 Hz) and gamma (30-100 Hz) oscillations. Beta activities were enhanced in the time frame 125-250 ms after stimulus onset, the VTC acted as main outflow hub, and network activities were negatively correlated with the difficult tasks. In contrast, gamma activities were elevated in the time frame 0-125 ms, the DLPFC acted as a main outflow hub, and network activities—specifically the FFA-PPA pair—were positively correlated with the difficult tasks. These findings significantly enhance our understanding of how sensory information enters and organizes within the SN and the VTC-DLPFC network, respectively in PDM.

Recollection, the process by which an item provokes the retrieval of associated information stored in the brain, is a key component of recognition memory. It is explored in this thesis through the use of a paradigm designed to allow the neural correlates of amount recalled to be identified through parametric fMRI analysis. A series of experiments were carried out during the development and optimisation of this paradigm in order to ensure that the various demands of this analysis were met. Subsequently this paradigm was applied during an fMRI experiment which provided data from both the encoding and retrieval stages of recollection.Whilst the development work was chiefly concerned with producing a suitable task design for the parametric fMRI analysis, these experiments provided some interesting results in their own right. The task design, which required participants to associate multiple item types within a story context, showed that there are significant differences in the frequency with which different stimuli are recollected. Participants were found to be particularly poor at recollecting faces whilst words were also shown to be recollected less frequently than either object or animal picture stimuli. A possible explanation for these differences may be related to the picture superiority effect although eye-tracking data collected from these experiments demonstrates large differences in viewing behaviour between different target stimulus types which is not correlated with later recall success. The amount of time participants spend engaging with the highly contextual scene item does predict later recall success.The fMRI analysis (Chapter 5) carried out during the encoding and retrieval stages of recollection found a variety of regions exhibiting a positive linear relationship with recollection at both these stages. This result provides support for the cortical reinstatement hypothesis of recollection despite the fact that the hippocampus only showed parametric modulation of activity during retrieval. It is proposed that parahippocampal activity during encoding and retrieval supports the recollection of contextual information whilst the same pattern of activity in parietal regions related to recollection may reflect the reinstatement of the global image of the story created during the encoding task.

No description available.

Os transtornos afetivos são altamente prevalentes dentre os transtornos mentais, principalmente Transtorno Afetivo Bipolar (TAB) e Depressão Maior Unipolar (DMU), apresentando altas taxas de morbi-mortalidade. Estudos prévios de Ressonância Magnética (RM) têm identificado anormalidades estruturais cerebrais em indivíduos com TAB e DMU quando comparados a controles normais. Entretanto, nenhum destes estudos foi realizado a partir da comparação direta entre pacientes com DMU e TAB de início recente, nem comparou separadamente tais grupos com amostras representativas de controles assintomáticos provenientes de mesma região geográfica. No presente estudo, definimos a priori que regiões do circuito córtico-límbico-talâmico-estriatal estariam alteradas quando comparados indivíduos com TAB, DMU e controles normais diretamente entre si, em amostra de pacientes com quadros graves de sintomatologia psicótica e pareada com controles normais selecionados na mesma área geográfica dos pacientes. Foram selecionados 46 pacientes (20 com DMU e 26 com TAB) que tiveram contato pela primeira vez com serviço de saúde mental após início de sintomas psicóticos e 62 controles normais. Tanto pacientes quanto controles foram submetidos à RM em aparelho de 1,5 Tesla. Os diagnósticos foram baseados no DSM-IV e confirmados após 1 ano da realização da RM. As imagens foram analisadas pelo método automatizado de processamento denominado morfometria baseada no voxel (voxel-based morphometry). A comparação entre os grupos mostrou redução significativa de substância cinzenta regional em pacientes com DMU comparados aos controles (p<0,05, corrigido para comparações múltiplas) em duas regiões cerebrais selecionadas a priori: córtex pré-frontal dorsolateral (CPFDL) bilateralmente e giro parahipocampal posterior esquerdo. Na comparação direta entre pacientes com DMU e TAB encontramos uma redução de substância cinzenta de CPFDL direito em pacientes com DMU, como tendência a significância estatística (p<0,10, corrigido para comparações múltiplas). Nossos achados mostram que anormalidades volumétricas de CPFDL e região temporal medial estão presentes em pacientes com DMU em primeiro episódio psicótico, mas não em pacientes com TAB com gravidade de sintomas semelhante. / Affective disorders are highly prevalent mental disorders, mainly Major Depressive Disorder (MDD) and Bipolar Disorder (BD), with high morbidity and mortality rates. Previous morphometric magnetic resonance imaging (MRI) studies have identified brain volumetric abnormalities in samples of subjects suffering from MDD or BD. However, none of these have conducted direct brain volume comparisons between patients with recent-onset MDD and BD, nor contrasted them separately against representative groups of asymptomatic controls recruited from exactly the same environment. In the present study, we defined a priori that brain regions involved in cortico-limbic-thalamic-striatal circuits would present volume abnormalities when comparing subjects with MDD and BD with psychotic features, in their first contact with the health care system in Brazil, and a control sample of next-door asymptomatic neighbors. Forty-six patients (20 MDD and 26 BD) and 62 controls were examined with MRI, using an equipment of 1.5 Tesla. Diagnoses were based on DSM-IV, and confirmed one year after scanning. Image processing was conducted using voxel-based morphometry methods. Between-group comparisons showed significant regional gray matter deficits in MDD subjects relative to controls (p<0.05, corrected for multiple comparisons), involving two brain regions where abnormalities in mood disorder patients had been predicted a priori: the dorsolateral prefrontal cortex (DLPFC) bilaterally and the left posterior parahippocampal gyrus. In the direct comparison between MDD and BD patients, the right-sided finding of decreased DLPFC gray matter in the former group retained trend levels of significance (p<0.10 corrected). Our findings indicate that significant structural abnormalities of the DLPFC and medial temporal region are present in patients with MDD in their first episode with psychotic features, but not in BD subjects with symptoms of similar severity.

Os transtornos afetivos são altamente prevalentes dentre os transtornos mentais, principalmente Transtorno Afetivo Bipolar (TAB) e Depressão Maior Unipolar (DMU), apresentando altas taxas de morbi-mortalidade. Estudos prévios de Ressonância Magnética (RM) têm identificado anormalidades estruturais cerebrais em indivíduos com TAB e DMU quando comparados a controles normais. Entretanto, nenhum destes estudos foi realizado a partir da comparação direta entre pacientes com DMU e TAB de início recente, nem comparou separadamente tais grupos com amostras representativas de controles assintomáticos provenientes de mesma região geográfica. No presente estudo, definimos a priori que regiões do circuito córtico-límbico-talâmico-estriatal estariam alteradas quando comparados indivíduos com TAB, DMU e controles normais diretamente entre si, em amostra de pacientes com quadros graves de sintomatologia psicótica e pareada com controles normais selecionados na mesma área geográfica dos pacientes. Foram selecionados 46 pacientes (20 com DMU e 26 com TAB) que tiveram contato pela primeira vez com serviço de saúde mental após início de sintomas psicóticos e 62 controles normais. Tanto pacientes quanto controles foram submetidos à RM em aparelho de 1,5 Tesla. Os diagnósticos foram baseados no DSM-IV e confirmados após 1 ano da realização da RM. As imagens foram analisadas pelo método automatizado de processamento denominado morfometria baseada no voxel (voxel-based morphometry). A comparação entre os grupos mostrou redução significativa de substância cinzenta regional em pacientes com DMU comparados aos controles (p<0,05, corrigido para comparações múltiplas) em duas regiões cerebrais selecionadas a priori: córtex pré-frontal dorsolateral (CPFDL) bilateralmente e giro parahipocampal posterior esquerdo. Na comparação direta entre pacientes com DMU e TAB encontramos uma redução de substância cinzenta de CPFDL direito em pacientes com DMU, como tendência a significância estatística (p<0,10, corrigido para comparações múltiplas). Nossos achados mostram que anormalidades volumétricas de CPFDL e região temporal medial estão presentes em pacientes com DMU em primeiro episódio psicótico, mas não em pacientes com TAB com gravidade de sintomas semelhante. / Affective disorders are highly prevalent mental disorders, mainly Major Depressive Disorder (MDD) and Bipolar Disorder (BD), with high morbidity and mortality rates. Previous morphometric magnetic resonance imaging (MRI) studies have identified brain volumetric abnormalities in samples of subjects suffering from MDD or BD. However, none of these have conducted direct brain volume comparisons between patients with recent-onset MDD and BD, nor contrasted them separately against representative groups of asymptomatic controls recruited from exactly the same environment. In the present study, we defined a priori that brain regions involved in cortico-limbic-thalamic-striatal circuits would present volume abnormalities when comparing subjects with MDD and BD with psychotic features, in their first contact with the health care system in Brazil, and a control sample of next-door asymptomatic neighbors. Forty-six patients (20 MDD and 26 BD) and 62 controls were examined with MRI, using an equipment of 1.5 Tesla. Diagnoses were based on DSM-IV, and confirmed one year after scanning. Image processing was conducted using voxel-based morphometry methods. Between-group comparisons showed significant regional gray matter deficits in MDD subjects relative to controls (p<0.05, corrected for multiple comparisons), involving two brain regions where abnormalities in mood disorder patients had been predicted a priori: the dorsolateral prefrontal cortex (DLPFC) bilaterally and the left posterior parahippocampal gyrus. In the direct comparison between MDD and BD patients, the right-sided finding of decreased DLPFC gray matter in the former group retained trend levels of significance (p<0.10 corrected). Our findings indicate that significant structural abnormalities of the DLPFC and medial temporal region are present in patients with MDD in their first episode with psychotic features, but not in BD subjects with symptoms of similar severity.