Cooperative Correlational and Discriminative Ensemble Classifier Learning for Early Dementia Diagnosis Using Morphological Brain Multiplexes

Dementia alters the brain wiring on different levels. However, these changes might be subtle particularly in patients with early mild cognitive impairment (eMCI). Hence, developing accurate diagnostic techniques for eMCI identification is critical for early intervention to prevent the onset of Alzheimer's disease (AD). There is a large body of machine-learning-based research developed for classifying different brain states (e.g., AD vs MCI) using neuroimaging data. These works can be fundamentally grouped into two categories. The first one uses correlational methods, such as canonical correlation analysis (CCA) and its variants, with the aim to identify most correlated features for diagnosis. The second one includes discriminative methods, such as feature selection methods and linear discriminative analysis (LDA) and its variants to identify brain features that discriminate between two brain states. However, existing methods examine these correlational and discriminative brain data independently, which overlooks the complementary information provided by both techniques, which could prove to be useful in data classification tasks. On the other hand, how early dementia affects cortical brain connections in morphology remains largely unexplored. To address these limitations, we propose a cooperative correlational and discriminative ensemble learning framework for eMCI diagnosis that leverages a brain network representation from multiple morphological networks, each derived from the cortical surface. Specifically, we devise the shallow convolutional brain multiplex (SCBM), which encodes both region-to-region and network-to-network relationships. Then, we represent each individual brain using a set of SCBMs, which are used to train an ensemble of CCA-SVM and LDA-based classifiers, cooperating to output the label for a new testing subject. Overall, our framework outperformed several state-of-the-art methods including independent correlational and discriminative methods.