Alzheimer’s disease (AD) is a neurodegenerative disease characterized by memory loss and declined cognitive functioning. Brain changes in AD involve grey matter atrophy and changes in brain... Show moreAlzheimer’s disease (AD) is a neurodegenerative disease characterized by memory loss and declined cognitive functioning. Brain changes in AD involve grey matter atrophy and changes in brain function. These different brain characteristics can respectively be visualized with structural and functional MRI scans. These MRI modalities have been used for AD classification, but studies typically only include a limited number of features. In this thesis we derived multiple types of features from each MRI modality, and combined those to discriminate AD patients and elderly controls. First, we showed that AD classification accuracy increases when combining multiple types of measures from a single MRI modality. This was shown for structural MRI scans in chapter 2, and for resting state fMRI scans in chapter 3. In chapter 4 we evaluated whether MRI based AD classification models can discriminate AD in a diverse clinical population as well. This worked to some extent, and it worked best using structural MRI scans. In chapter 5 we used baseline multimodal MRI scans from the same diverse clinical population to predict two-year follow-up cognitive decline. Decline was predicted above chance level for the MMSE, but not for six other neuropsychological tests. Show less
Although the outcomes of our daily-life risky decisions are often unknown (e.g., receiving or not receiving a fine after running a red light), the probabilities of these outcomes may also vary in... Show moreAlthough the outcomes of our daily-life risky decisions are often unknown (e.g., receiving or not receiving a fine after running a red light), the probabilities of these outcomes may also vary in uncertainty. That is, the probabilities may be known (risk) or unknown (ambiguity), which influences risk taking behavior to a great extent. A developmental phase associated with heightened risk taking is adolescence, yet how adolescents process risk and ambiguity, and the relation with real-life risk taking, remain elusive. Moreover, individual differences in observed risk taking behavior remain largely overlooked. In this PhD thesis risk and ambiguity processing in adolescents were decomposed using behavioral economics and fMRI, and related to real-life risk taking. The results indicated that risk and ambiguity differentially impact risk-taking behavior, and are processed by different neural mechanisms. In addition, individual variation in task-related and real-life risk taking highlighted that adolescence is not a phase of heightened risk taking for everyone. Moreover, it was found that real-life risk-taking and prosocial tendencies were both predicted by fun seeking, suggesting this trait may make individuals differentially susceptible to positive or negative outcomes. Together, this thesis points towards a more nuanced perspective on adolescent risk taking and its underlying components. Show less
