Biomarcadores topográficos basados en electroencefalogramas recopilados durante tareas de memoria operacional para apoyar el diagnóstico precoz de la enfermedad de Alzheimer

En esta investigación se diseñaron tres estudios para mejorar y validar biomarcadores topográficos basados en el análisis computacional de electroencefalogramas (EEG) recolectados durante la ejecución de tareas de memoria de trabajo N-back, con el objetivo de brindar soporte para el diagnóstico precoz del deterioro cognitivo leve y de la enfermedad de Alzheimer. En el primer estudio se analizaron los potenciales relacionados a eventos, en la que se encontró diferencias significativas en el intervalo de 400 a 700 ms post estímulo en el componente P450. En el segundo estudio se analizaron los registros electroencefalográficos en las tareas de memoria operacional, encontrando diferencias significativas principalmente en las regiones del lóbulo frontal y temporal. Finalmente, en el tercer estudio se hizo la clasificación automática a través de técnicas de aprendizaje de máquina con clasificadores basados en el lenguaje de programación Python, el cual alcanzó una precisión, sensibilidad y especificidad en torno al 94%, este método de extracción de características logra superar los mejores desempeños reportados en la literatura, lo que indica que esta técnica puede representar una herramienta clínicamente relevante para apoyar el diagnóstico temprano de deterioro cognitivo leve y de la enfermedad de Alzheimer.doença de Alzheimer (DA) é uma doença neurodegenerativa que afeta milhões de pessoas em todo o mundo. Além disso, pessoas com comprometimento cognitivo leve (CCL) estão em um grupo de risco que deve ser seguido atentamente, pois há uma alta probabilidade de evolução para DA. Nesta pesquisa, três estudos foram delineados para aprimorar e validar biomarcadores topográficos baseados na análise computacional do eletrencefalograma (EEG) coletado durante a execução de tarefas de memória operacional N-back, com o objetivo de fornecer suporte ao diagnóstico precoce do CCL e da DA. Os participantes foram 15 pacientes com diagnóstico de DA, 21 indivíduos com diagnóstico de CCL e 27 idosos saudáveis (IS) para o grupo controle. Os sujeitos foram submetidos a uma tarefa N-back visual de três níveis, com dificuldade ascendente na carga de memória operacional, durante a qual foram registrados sinais de EEG (32 canais).Brasil. Ministério da Educação. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes

Early diagnosis of mild cognitive impairment and Alzheimer’s with event-related potentials and event-related desynchronization in N-back working memory tasks

Background and Objective: In this study we investigate whether or not event-related potentials (ERP) and/or event-related (de)synchronization (ERD/ERS) can be used to differentiate between 27 healthy elderly (HE), 21 subjects diagnosed with mild cognitive impairment (MCI) and 15 mild Alzheimer’s disease (AD) patients. Methods: Using 32-channel EEG recordings, we measured ERP responses to a three-level (N-back, N = 0,1,2) visual working memory task. We also performed ERD analysis over the same EEG data, dividing the full-band signal into the well-known delta, theta, alpha, beta and gamma bands. Both ERP and ERD analyses were followed by cluster analysis with correction for multicomparisons whenever significant differences were found between groups. Results: Regarding ERP (full-band analysis), our findings have shown both patient groups (MCI and AD) with reduced P450 amplitude (compared to HE controls) in the execution of the non-match 1-back task at many scalp electrodes, chiefly at parietal and centro-parietal areas. However, no significant differences were found between MCI and AD in ERP analysis whatever was the task. As for sub-band analyses, ERD/ERS measures revealed that HE subjects elicited consistently greater alpha ERD responses than MCI and AD patients during the 1-back task in the match condition, with all differences located at frontal, central and occipital regions. Moreover, in the non-match condition, it was possible to distinguish between MCI and AD patients when they were performing the 0-back task, with MCI presenting more desynchronization than AD on the theta band at temporal and fronto-temporal areas. In summary, ERD analyses have revealed themselves more valuable than ERP, since they showed significant differences in all three group comparisons: HE vs. MCI, HE vs. AD, and MCI vs. AD. Conclusions: Based on these findings, we conclude that ERD responses to working memory (N-back) tasks could be useful not only for early MCI diagnosis or for improved AD diagnosis, but probably also for assessing the likelihood o