Estudio de alteraciones en la conectividad estructural y funcional del cerebro basado en imágenes de resonancia magnética de pacientes con psicosis temprana.
Loading...
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
En las últimas décadas, investigaciones se han centrado en comprender las bases de la psicosis y sus posibles causas, donde se incluyen factores genéticos, anomalías cerebrales y factores ambientales. Un enfoque clave en la actualidad es el estudio de las fibras de la materia blanca, debido a su importancia en las conexiones del cerebro. Estas juegan un papel crucial en la transmisión de señales, y su disfunción ha sido asociada con la aparición de síntomas psicóticos.
Esta tesis propuso estudiar las alteraciones en la conectividad cerebral en pacientes con psicosis temprana, a través del análisis conjunto de imágenes de resonancia magnética por difusión (dMRI) y resonancia funcional (fMRI). El objetivo principal fue identificar y analizar alteraciones en la estructura de la materia blanca y cambios en la conectividad funcional entre regiones cerebrales, ofreciendo nuevas perspectivas en la comprensión de las alteraciones presentes en la psicosis.
Para esto, se empleó la base de datos del “Human Connectome Project for Early Psychosis”, con datos de 75 pacientes con psicosis y 55 controles sanos. El análisis dMRI se centró en fascículos de fibras largas y cortas, empleando medidas derivadas de las imágenes del tensor de difusión (DTI) y del muestreo de Q generalizado (GQI). A su vez, el análisis de fMRI se basó en la construcción de matrices de conectividad funcional, evaluando su organización a través de métricas locales y globales de teoría de grafos.
Los resultados mostraron alteraciones estructurales más evidentes en fascículos largos, especialmente en la anisotropía cuantitativa, con diferencias significativas en tractos comisurales, frontales y subcorticales. En cuanto a la conectividad funcional, la métrica de centralidad del vector propio destacó por identificar varios nodos con cambios relevantes, sugiriendo una reorganización jerárquica en la red cerebral de pacientes. Este hallazgo fue complementado por resultados en el coeficiente de agrupamiento, lo que apunta a una posible disrupción tanto local como global en la conectividad. Estos cambios fueron consistentes al aplicar análisis complementarios como reducción de dimensionalidad mediante PCA y clasificación supervisada con el modelo SVM.
A futuro, se plantea ampliar la muestra y considerar nuevas variables clínicas, lo cual permitiría una interpretación más completa. También se propone validar externamente los modelos clasificatorios y considerar la inclusión de sujetos con psicosis afectiva, con el objetivo de explorar similitudes y diferencias en sus patrones de conectividad. El uso combinado de estas técnicas permite una perspectiva más completa al poder complementar resultados para la comprensión de las alteraciones cerebrales en la psicosis temprana. Este estudio busca contribuir al estudio y compresión de cómo afectan la integridad de las fibras y su conectividad en la presencia de síntomas psicóticos.
In recent decades, research has focused on understanding the basis of psychosis and its possible causes, including genetic factors, brain abnormalities, and environmental factors. A key focus today is the study of white matter fibers, due to their importance in brain connections. These fibers play a crucial role in signal transmission, and their dysfunction has been associated with the onset of psychotic symptoms. This thesis proposed to study alterations in brain connectivity in patients with early psychosis through the joint analysis of diffusion magnetic resonance imaging (dMRI) and functional magnetic resonance imaging (fMRI). The main objective was to identify and analyze alterations in white matter structure and changes in functional connectivity between brain regions, offering new perspectives on the understanding of alterations present in psychosis. To this end, the database of the “Human Connectome Project for Early Psychosis” was used, with data from 75 patients with psychosis and 55 healthy controls. The dMRI analysis focused on long and short fiber tracts, using measures derived from diffusion tensor imaging (DTI) and generalized q-sampling (GQI). In turn, the fMRI analysis was based on the construction of functional connectivity matrices, assessing their organization through local and global graph theory metrics. The results showed more evident structural alterations in long fascicles, especially in “quantitative anisotropy”, with significant differences in commissural, frontal, and subcortical tracts. In terms of functional connectivity, the “eigenvector centrality” metric stood out for identifying several nodes with relevant changes, suggesting a hierarchical reorganization in the brain network of patients. This finding was complemented by results in the “clustering coefficient”, which points to a possible disruption in both local and global connectivity. These changes were consistent when applying complementary analyses such as dimensionality reduction using PCA and supervised classification with the SVM model. In the future, expanding the sample and incorporating new clinical variables could facilitate a more comprehensive interpretation. The study further proposes to externally validate the classification models and consider the inclusion of subjects with affective psychosis, with the aim of exploring similarities and differences in their connectivity patterns. The combined use of these techniques allows for a more complete perspective by complementing results for understanding brain alterations in early psychosis. This study seeks to contribute to the study and understanding of how fiber integrity and connectivity are affected in the presence of psychotic symptoms.
In recent decades, research has focused on understanding the basis of psychosis and its possible causes, including genetic factors, brain abnormalities, and environmental factors. A key focus today is the study of white matter fibers, due to their importance in brain connections. These fibers play a crucial role in signal transmission, and their dysfunction has been associated with the onset of psychotic symptoms. This thesis proposed to study alterations in brain connectivity in patients with early psychosis through the joint analysis of diffusion magnetic resonance imaging (dMRI) and functional magnetic resonance imaging (fMRI). The main objective was to identify and analyze alterations in white matter structure and changes in functional connectivity between brain regions, offering new perspectives on the understanding of alterations present in psychosis. To this end, the database of the “Human Connectome Project for Early Psychosis” was used, with data from 75 patients with psychosis and 55 healthy controls. The dMRI analysis focused on long and short fiber tracts, using measures derived from diffusion tensor imaging (DTI) and generalized q-sampling (GQI). In turn, the fMRI analysis was based on the construction of functional connectivity matrices, assessing their organization through local and global graph theory metrics. The results showed more evident structural alterations in long fascicles, especially in “quantitative anisotropy”, with significant differences in commissural, frontal, and subcortical tracts. In terms of functional connectivity, the “eigenvector centrality” metric stood out for identifying several nodes with relevant changes, suggesting a hierarchical reorganization in the brain network of patients. This finding was complemented by results in the “clustering coefficient”, which points to a possible disruption in both local and global connectivity. These changes were consistent when applying complementary analyses such as dimensionality reduction using PCA and supervised classification with the SVM model. In the future, expanding the sample and incorporating new clinical variables could facilitate a more comprehensive interpretation. The study further proposes to externally validate the classification models and consider the inclusion of subjects with affective psychosis, with the aim of exploring similarities and differences in their connectivity patterns. The combined use of these techniques allows for a more complete perspective by complementing results for understanding brain alterations in early psychosis. This study seeks to contribute to the study and understanding of how fiber integrity and connectivity are affected in the presence of psychotic symptoms.
Description
Tesis presentada para optar al grado de Magíster en Ciencias de la Ingeniería con mención en Ingeniería Eléctrica.
Keywords
Trastornos psicóticos, Cerebro Investigaciones, Resonancia magnética