Psychophysiological and FMRI responses during various extended cognitive tasks: a comparison of initial and sustained activity

Abstract

This doctoral thesis explores the complex dynamics of cognitive load, emphasizing its neural and psychophysiological underpinnings, with a focus on the frontoparietal multiple demand (MD) regions and the default mode network (DMN). Through a series of experiments; spanning line orientation, tactile decision-making, and auditory n-back tasks, the research investigates distinct activation patterns during task initiation and execution. By examining the complex relationship between neural activation and psychophysiological responses, particularly pupil dilation, the study reveals the multifaceted nature of cognitive load and its condition-dependent manifestations. Findings challenge the traditional view of cognitive load as a singular construct, demonstrating that it engages multiple, context-specific neural mechanisms. Nonlinear activation patterns in MD regions highlight distinct roles during task initiation and sustained engagement, while the DMN exhibits overlapping functions with MD regions, particularly during early task phases. Notably, the bilateral temporoparietal junction (TPJ) emerges as a key node, bridging traditional boundaries between these networks. Pupil dilation further mirrors these neural dynamics, underscoring its potential as a robust, non-invasive marker of cognitive load. The research contributes to a deeper understanding of how cognitive resources are dynamically allocated across varying task demands. Evidence from this interdisciplinary investigation highlights the interplay between MD and DMN regions, suggesting an integrated framework of cognitive control and self-referential processing. Insights gained extend beyond theoretical implications, offering applications in clinical settings, education, and human-computer interaction. This includes potential advancements in diagnosing and treating neuropsychiatric disorders, optimizing cognitive training programs, and enhancing technological interfaces. By integrating neuroimaging, psychophysiological, and behavioral paradigms, this thesis provides a comprehensive account of the neural mechanisms governing cognitive load. It advances our understanding of the intricate dynamics of brain networks, offering a foundation for innovative approaches to assessing and managing cognitive demands across diverse contexts.