Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Abnormal connectivity of the intrinsic anticorrelated networks, the task-negative network (TNN) and task-positive network (TPN), is implicated in schizophrenia. Comparisons between schizophrenic patients and their unaffected siblings offer an opportunity to further understand illness susceptibility and pathophysiology. We hypothesized that schizophrenic patients would demonstrate hyperconnectivity in the intrinsic networks and that similar, but less pronounced, hyperconnectivity would be evident in the networks of the unaffected siblings. Resting-state functional magnetic resonance images were obtained from schizophrenic patients (n=25), their unaffected siblings (n=25), and healthy controls (n=25). The posterior cingulate cortex/precuneus (PCC/PCu) and right dorsolateral prefrontal cortex (DLPFC) were used as seed regions to identify the TNN and TPN. Interregional connectivity strengths were analyzed using overlapped intrinsic networks composed of regions common to the intrinsic networks of the three subject groups. In the TNN, schizophrenic patients alone demonstrated hyperconnectivity between the PCC/PCu and left inferior temporal gyrus and between the ventral medial prefrontal cortex and the right lateral parietal cortex. Both schizophrenic patients and their unaffected siblings showed increased connectivity in the TNN between the bilateral inferior temporal gyri. In the TPN, schizophrenic patients showed hyperconnectivity between the left DLPFC and right inferior frontal gyrus relative to unaffected siblings, though this trend only approached statistical significance in comparison to healthy controls. Resting-state hyperconnectivity of the intrinsic networks may underlie the pathophysiology of schizophrenia by disrupting network coordination. Similar, though milder, hyperconnectivity in unaffected siblings of schizophrenic patients may contribute to their cognitive deficits and increased risk to develop schizophrenia.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Orientador: Fernando Cendes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-22T17:03:57Z (GMT). No. of bitstreams: 1 Coan_AnaCarolina_D.pdf: 6791315 bytes, checksum: 88120ea79f2fe1f4f6c17ed50c0e32d1 (MD5) Previous issue date: 2013 / Resumo: Introdução: A epilepsia de lobo temporal mesial (ELTM) não é uma doença única, mas um conjunto de diferentes síndromes com etiologias diversas, que têm uma apresentação clínica e eletroencefalográfica comum. A compreensão dos diferentes tipos de ELTM é fundamental para o desenvolvimento de terapêuticas adequadas e individualizadas. Objetivo: Avaliar e comparar a ocorrência de alterações estruturais e funcionais na ELTM com (ELTM-EH) e sem (ELTM-NL) sinais de esclerose hipocampal (EH) nas imagens de ressonância magnética (RM) e relacionar essas alterações com a resposta ao tratamento. Métodos: Pacientes com diagnóstico de ELTM, e sem lesões estruturais exceto por sinais de EH, foram avaliados através de dados clínicos e por exames de RM de 3Tesla estruturais e funcionais. Os pacientes foram classificados em ELTM com (ELTM-EH) ou sem (ELTM-NL) sinais de EH através da quantificação de volume e sinal do hipocampo. Quantificação do volume da amígdala também foi realizada. Análise de volume da substância cinzenta (SC) cerebral foi realizada através da técnica de Morfometria Baseada em Voxel (VBM). Análise de alterações funcionais relacionadas às descargas epilépticas interictais (DEIs) foi realizada com o uso concomitante de EEG e RM funcional (EEG-RMf). Resultados: A quantificação de volume e sinal hipocampal nos exames de RM de 203 pacientes com ELTM aumentou em 28% a sensibilidade de detecção de sinas de EH em comparação com a análise visual. Subgrupos de pacientes com ELTM-EH e ELTM-NL e hipertrofia de amígdala foram observados. Após exclusão de pacientes com a lateralidade do foco epiléptico indefinida, 172 pacientes (122 ELTM-EH e 50 ELTM-NL) foram avaliados clinicamente e pela técnica de VBM. O grupo ELTM-NL apresentou idade de início de crises mais elevada e menor duração da epilepsia, além de antecedente familiar de epilepsia mais frequente do que ELTM-EH. ELTM-EH e ELTM-NL apresentaram atrofia de SC difusa, incluindo tálamos e córtex sensório motor bilaterais. Diferentemente do grupo ELTM-EH, os pacientes com ELTM-NL não apresentaram atrofia em regiões temporais e apresentaram atrofia pronunciada em córtex órbito-frontal ipsilateral ao foco epiléptico. A subdivisão dos grupos de acordo com a resposta à droga antiepiléptica (DAE) revelou atrofia de SC difusa em ELTM-EH benignos e refratários, a pesar do segundo grupo apresentar atrofia mais pronunciada principalmente em áreas sem conexões diretas com o hipocampo. Diferentemente, atrofia de SC foi observada apenas nos pacientes com ELTM-NL e crises refratárias. As redes neuronais funcionais relacionadas com as DEIs deferiram entre os grupos ELTM-EH e ELTM-NL e foram distintas das redes estruturais detectadas pelo VBM. Nos exames funcionais, em ambos os grupos, supressão da atividade em áreas da Default Mode Network foi observada concomitantemente às DEIs e esse padrão foi relacionado a melhor prognóstico cirúrgico em pacientes com crises refratárias. Conclusão: Alterações estruturais e funcionais são distintas em ELTM-EH e ELTM-NL. Diferentes redes neuronais estão relacionadas ao prognóstico clínico e cirúrgico na ELTM. Conhecimento detalhado das redes neuronais envolvidas nos diversos tipos de ELTM e da interação dinâmica entre elas deve contribuir para o aprimoramento do tratamento desses pacientes / Abstract: Introduction: Mesial temporal lobe epilepsy (MTLE) is not a single disease but a group of different diseases with distinct etiologies that share common clinical and EEG characteristics. Understanding the different types of MTLE is fundamental to the development of more appropriate and individualized therapies for ictal phenomena and comorbidities of each patient. Objective: To evaluate and compare the occurrence of structural and functional abnormalities of MTLE with (MTLE-HS) and without (MTLE-NL) signs of hippocampal sclerosis (HS) in magnetic resonance imaging (MRI) and to correlate these abnormalities with the response to treatment. Methods: Patients diagnosed with MTLE defined by clinical and electroencephalographic, and without structural lesions except for signs of HS were evaluated with clinical data and structural and functional 3T MRIs. Patients were classified as MTLE with (MTLE-HS) or without (TLE-NL) signs of HS by quantifying and hippocampal volume and signal. Amygdala volume quantification was also performed. Analysis of volume of brain gray matter (GM) of both groups was performed using the technique of voxel-based morphometry (VBM). Analysis of functional changes related to interictal epileptic discharges (IED) in both groups was performed with concomitant use of EEG and functional MRI (EEG-fMRI). Results: The quantification of volume and hippocampal signal in MRI scans of 203 patients with MTLE increased in 28% the sensitivity of detecting signs of HS compared with the visual analysis. Subgroups of patients with MTLE-HS and MTLE-NL and amygdala hypertrophy were observed. After exclusion of patients with undefined or bilateral epileptic focus, a group of 172 patients (122 ELTM-HS and 50 ELTM-NL) were evaluated with VBM technique. Patients with MTLE-NL had higher age of epilepsy onset and shorter duration of epilepsy as well as more frequent family history of epilepsy than patients with MTLE-HS. MTLE-HS and MTLE-NL showed diffuse GM atrophy, including bilateral sensorimotor cortex and thalamus. Different from MTLE-HS group, patients with MTLE-NL showed no atrophy in mesial and neocortical temporal regions and had pronounced atrophy in the orbito-frontal cortex ipsilateral to the epileptic focus. The subdivision of the groups according to the response to antiepileptic drug (AED) revealed diffuse GM atrophy in both benign and refractory and MTLE-HS, despite the second group exhibit more pronounced atrophy specially in areas with no direct connections with the hippocampus. Differently, GM atrophy was observed only in patients with MTLE-NL and refractory seizures. The functional neuronal networks related to IED were different in MTLE-HS and MTLE-NL groups and were distinct from the structural networks detected by VBM technique. Functional analysis revealed in both groups suppression of activity in brain areas compatible with the Default Mode Network (DMN) concomitantly with IED and this pattern was related to better surgical outcome in patients with AED resistant seizures. Conclusion: Structural and functional networks abnormalities are distinct in MTLE-HS and MTLE-NL. Different neural networks are related to surgical and clinical prognosis in MTLE. Detailed knowledge of the neural networks involved in various types of MTLE and the dynamic interaction between them might contribute to improving the treatment of seizures and comorbidities in these patients / Doutorado / Neurociencias / Doutora em Fisiopatologia Médica

Resting-state functional magnetic resonance imaging (rs-fMRI) is a non-invasive neuroimaging technique that utilizes spontaneous low-frequency fluctuations of blood-oxygenation-level dependent (BOLD) signals to examine resting-state functional connectivity in the brain. In the past two decades, this technique has been increasingly utilized to investigate properties of large-scale functional neural networks as well as their alterations in various cognitive and disease states. However, much less is known about large-scale functional neural networks of the rodent brain, particularly in the awake state. Therefore, we attempted to unveil local and global functional connectivity in awake rat through a combination of seed-based analysis, independent component analysis and graph-theory analysis. In the current studies, we revealed elementary local networks and their global organization in the awake rat brain. We further systematically compared the functional neural networks in awake and anesthetized states, revealing that the rat brain was locally reorganized while maintaining global topological properties from awake to anesthetized states. Furthermore, specific neural circuitries of the rat brain were examined using resting-state fMRI. First anticorrelated functional connectivity between infralimbic cortex and amygdala were found to be evident with different preprocessing methods (global signal regression, regression of ventricular and white matter signal and no signal regression). Secondly the thalamocortical connectivity was mapped for individual thalamic groups, revealing group-specific functional cortical connections that were generally consistent with known anatomical connections in rat. In conclusion, large-scale neural networks can be robustly and reliably studied using rs-fMRI in awake rat, and with this technique we established a baseline of local and global neural networks in the awake rat brain as well as their alterations in the anesthetized condition.

Understanding how memory is formed requires looking beyond the genes involved to the neural circuitry and temporal aspects of memory. In this dissertation I have focused my investigation on Dorsal Paired Medial (DPM) neurons, two modulatory neurons essential for memory in Drosophila. DPM neurons highly express the amnesiac (amn) gene, which encodes for a putative pre-pro-neuropeptide. amn function in DPM neurons is required for memory. Here I provide evidence that DPM neurons are cholinergic and that acetylcholine (ACh) and AMN act as co-transmitters essential for DPM function. In order to investigate the temporal requirements of DPM output I blocked transmitter release during discrete intervals in the memory process using shibirets1 and tested flies for shock and sugar-reinforced memory. These experiments demonstrated that stable memory requires persistent transmitter release from DPM neurons. Furthermore these results suggest AMN and DPM neurons act as general stabilizers of mushroom body dependent memory. To further investigate the neural circuitry underlying DPM function I disrupted DPM projections onto the mushroom body lobes by ectopically expressing DScam17-2::GFP in DPM neurons. Flies with DPM neurons that predominantly project to the mushroom body α´/β´ lobes exhibit normal memory, and blocking transmitter release from the mushroom body prime lobes neurons themselves abolishes memory indicating DPM neuron-mushroom body α´/β´ neuron interaction that are critical for memory. Taken together, the experimental evidence presented here are used to provide a rudimentary model of the neural circuitry involved in memory stability, where DPM neurons form a recurrent feedback loop with the mushroom body α´/β´ lobe neurons and act to stabilize odorspecific conditioned memories at Kenyon cell synapses.

Retinal ganglion cell (RGC) axon arbors within the optic tectum are refined in development through a dynamic process of activity-dependent remodeling. The synaptic adhesion molecule N-cadherin is a candidate for mediating selective stabilization and elaboration of RGC axons due to its localization to perisynaptic sites and its modifiability by neural activity. RGCs of Xenopus tadpoles were co-transfected with plasmids encoding a dominant negative N-cadherin (N-cadDeltaE) and eGFP or eYFP. Using two-photon in vivo time-lapse imaging, we found that axons expressing N-cadDeltaE became less elaborate than controls over three days of daily live imaging. Shorter interval time-lapse imaging of axons expressing synaptophysin-GFP to visualize putative synaptic sites revealed that N-cadDeltaE expressing axons form fewer stable branches than controls and that stabilization of axonal branches at synaptic sites is altered. We conclude that N-cadherin participates in the stabilization of axonal branches in the Xenopus retinotectal system.

No description available.