Phd in PSYCHOLOGY AND COGNITIVE SCIENCE

Thesis title: Higher-Level Executive Functions in Healthy Aging and Aging with Mild Cognitive Impairment: The Role of Cognitive Flexibility

Executive functions (EFs) are higher-level cognitive functions that allow managing internal and external stimuli to regulate behavior. Over the past century, several authors have proposed their models of EFs. One of these is Diamond's model, which classifies EFs into core EFs (inhibitory control, working memory, and cognitive flexibility) and higher-level EFs (planning and fluid intelligence). In particular, cognitive flexibility, although classified as a core EF, plays an intermediate role because its development is based on the other two core EFs. Mild Cognitive Impairment (MCI) is a syndrome that occurs between healthy and pathological aging. Individuals with MCI show several dysfunctions in cognitive domains, such as in EFs. The hypothesis behind this work is that cognitive flexibility has two components, i.e., switching and set-shifting, which can predict higher-level EFs in adulthood, physiological aging, and MCI. The general aim of this study is to examine the relationship between cognitive flexibility and higher-level EFs in physiological aging and MCI by (I) defining what the components of cognitive flexibility are; (II) examining how global cognitive functioning mediates the role of cognitive flexibility components on higher-level EFs; (III) assessing how these components predict higher-level EFs; (IV) evaluating how these components operate in adults and older adults in predicting higher-level EFs. In addition, analyze the relationship between cognitive flexibility and higher-level EFs in healthy adults and adults with MCI by (V) assessing the differences between healthy aging and with MCI in EFs; (VI) evaluating how cognitive flexibility components operate in healthy adults and adults with MCI in predicting higher-level EFs. In the first study, 108 participants were included (50 adults and 58 older adults); in the second study, 90 participants were included (45 healthy and 45 MCI). The results of exploratory and confirmatory factor analyses showed that cognitive flexibility consists of two components: set-shifting and task-switching. The mediation analysis highlighted that the effects of task-switching and set-shifting on higher-level EFs are mediated differently from global cognitive functioning. Furthermore, linear regressions indicated that set-shifting is the variable that best predicts planning and fluid intelligence in physiological aging and MCI. Moreover, the MANOVA analysis revealed that individuals with MCI exhibit poorer performance in cognitive flexibility and higher-level EFs. In conclusion, these studies showed that cognitive flexibility is a construct that incorporates different abilities, which can impact higher-level executive functions differently. This is important from a preventive perspective because acting preventively on cognitive flexibility can prevent and/or mitigate pathological aging.