Precuneus Failures in Subjects of the PSEN1 E280A Family at Risk of Developing Alzheimer's Disease Detected Using Quantitative Electroencephalography.

BACKGROUND: Presenilin-1 (PSEN1) mutations are the most common cause of familial early onset Alzheimer's disease (AD). The PSEN1 E280A (E280A) mutation has an autosomal dominant inheritance and is involved in the production of amyloid-ß. The largest family group of carriers with E280A mutation is found in Antioquia, Colombia. The study of mutation carriers provides a unique opportunity to identify brain changes in stages previous to AD. Electroencephalography (EEG) is a low cost and minimally invasiveness technique that enables the following of brain changes in AD. OBJECTIVE: To examine how previous reported differences in EEG for Theta and Alpha-2 rhythms in E280A subjects are related to specific regions in cortex and could be tracked across different ages. METHODS: EEG signals were acquired during resting state from non-carriers and carriers, asymptomatic and symptomatic subjects from E280A kindred from Antioquia, Colombia. Independent component analysis (ICA) and inverse solution methods were used to locate brain regions related to differences in Theta and Alpha-2 bands. RESULTS: ICA identified two components, mainly related to the Precuneus, where the differences in Theta and Alpha-2 exist simultaneously at asymptomatic and symptomatic stages. When the ratio between Theta and Alpha-2 is used, significant correlations exist with age and a composite cognitive scale. CONCLUSION: Theta and Alpha-2 rhythms are altered in E280A subjects. The alterations are possible to track at Precuneus regions using EEG, ICA, and inverse solution methods.

Successful Object Encoding Induces Increased Directed Connectivity in Presymptomatic Early-Onset Alzheimer's Disease.

BACKGROUND: Recent studies report increases in neural activity in brain regions critical to episodic memory at preclinical stages of Alzheimer's disease (AD). Although electroencephalography (EEG) is widely used in AD studies, given its non-invasiveness and low cost, there is a need to translate the findings in other neuroimaging methods to EEG. OBJECTIVE: To examine how the previous findings using functional magnetic resonance imaging (fMRI) at preclinical stage in presenilin-1 E280A mutation carriers could be assessed and extended, using EEG and a connectivity approach. METHODS: EEG signals were acquired during resting and encoding in 30 normal cognitive young subjects, from an autosomal dominant early-onset AD kindred from Antioquia, Colombia. Regions of the brain previously reported as hyperactive were used for connectivity analysis. RESULTS: Mutation carriers exhibited increasing connectivity at analyzed regions. Among them, the right precuneus exhibited the highest changes in connectivity. CONCLUSION: Increased connectivity in hyperactive cerebral regions is seen in individuals, genetically-determined to develop AD, at preclinical stage. The use of a connectivity approach and a widely available neuroimaging technique opens the possibility to increase the use of EEG in early detection of preclinical AD.

Creación de plantillas personalizadas para la implementación de morfometría basada en vóxeles / Custom Template Construction to Implement Voxel-Based Morphometry

Introducción: La morfometría basada en vóxeles es una técnica desarrollada para caracterizar diferencias cerebrales in vivo, usando imágenes estructurales por resonancia magnética de manera automática, sin necesidad de definir regiones de interés. Dentro del procesamiento de las imágenes se encuentran tareas que requieren el uso de plantillas de referencia. Sin embargo, el uso de plantillas que difieran demográficamente de la población de estudio puede llevar a interpretaciones erróneas de los resultados. Objetivo: Describir la construcción de plantillas que capturen la variabilidad y las características propias de la población en estudio, adaptando el uso de la morfometría basada en vóxeles. Metodología: De una población de 50 sujetos voluntarios sanos se construyeron plantillas de sustancia gris, sustancia blanca y líquido cefalorraquídeo, que luego fueron comparadas con la plantilla del Instituto Neurológico de Montreal, y posteriormente utilizadas como datos de referencias en los procesamientos de morfometría basada en vóxeles bajo una prueba de género. Los resultados fueron comparados con los obtenidos al utilizar las plantillas del instituto y validados según estudios similares presentados en la literatura. Resultados: El uso del conjunto de algoritmos DARTEL en la metodología propuesta permitió generar plantillas con mejor detalle morfológico, y la implementación de estas en morfometría basada en vóxeles aumentó la sensibilidad de la técnica. Conclusiones: Las plantillas generadas representan mejor la variabilidad local de la población y posibilitan la personalización de técnicas como la morfometría basada en vóxeles, al mejorar los resultados de la segmentación y otras tareas de procesamiento.

Introduction: Voxel-based morphometry (VBM) has been developed to characterize in vivo brain anatomic and functional differences using magnetic resonance imaging (MRI) automatically, without having to define regions of interest. Compared to other techniques, VBM does not require manual delineation of regions of interest. Image processing includes tasks which require the use of reference templates. However, the use of templates that differ demographically from the studied population could lead to incorrect interpretations of the results. Objective: To scribe the construction of templates which describe the variability and the specific morphological characteristics of the studied population. Methodology: Gray matter, white matter and cerebrospinal fluid templates were built from a population of 50 willing healthy persons. These templates were then compared with the template of the Montreal Neurological Institute and were subsequently used as reference data in the processing of voxel-based morphometry in a gender test. The results were compared with those obtained by using templates of the Montreal Neurological Institute and validated by similar studies reported in the literature. Results: We found that the use of DARTEL algorithms in the suggested methodology can generate better morphological detail templates, and the implementation of their algorithms in voxelbased morphometry increases the sensitivity of the technique. Conclusions: Our templates improve local variability of the population and enable personalization of techniques such as voxel-based morphometry, by improving segmentation results and other processing tasks.