Longitudinal data analysis with statistical and machine learning methods in neuroscience

Çakar, Serenay
Exploration of brain activity under different conditions has been subject to many neuroscience studies. The recent developments in cognitive studies provide the opportunity to work on neural correlates of specific cognitive processes such as working memory, decision making, response inhibition, perception, and sensation. Brain response studies constitute multidimensional, multilevel or nested data sets formed by different parts of the brain of individuals. Hence, it is of significant importance to implement data analysis methods appropriate for the longitudinal structures. However, previous studies on brain response utilized methods that do not consider the dependency, multilevel and nested structure. In this thesis, we propose to apply different statistical and machine learning methods on cognitive data to fill the aforementioned deficiencies. We analyze open-access data, including optical density measures collected from 36 locations of the brain within 26 subjects through functional near-infrared spectroscopy (fNIRS). fNIRS signals are used to measure relative changes in oxyhemoglobin and deoxyhemoglobin concentrations. The nested structure of the data, which is having observations from different brain regions within subjects, is also considered. The content of this thesis provides a comprehensive implementation and comparison of several statistical and machine learning algorithms which are Linear Mixed Model (LMM) and its robustified version, Generalized LMM Tree (GLMM tree), Random Effects Expectation-Maximization Tree (RE-EM tree), Unbiased RE-EM tree, Longitudinal Classification and Regression Tree, and Gaussian Process Boosting. According to one of our findings, the GLMM tree with nested structure shows the best predictive performance as it provides the lowest model performance metrics. However, there is a trade-off between accuracy and speed since the speed of this algorithm is lower compared to other methods except robustified LMM.


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Citation Formats
S. Çakar, “Longitudinal data analysis with statistical and machine learning methods in neuroscience,” M.S. - Master of Science, Middle East Technical University, 2022.