Neural mechanisms of the wandering mind

Abstract

The human mind wanders spontaneously and pervasively throughout daily life, pursuing trains of thought that are untethered to the world around us. Although mapping the many facets of mind wandering has become a compelling objective in the cognitive neurosciences, researchers have yet to achieve a congruous mechanistic account of its neurobiological underpinnings. In this thesis, a multidisciplinary strategy was implemented to illuminate the various aspects of mind wandering during passive rest and cognitive task performance. To more confidently detect changes in attention, we combined spatially localized and temporally precise features from different neural modalities, subjective experience, and changes in moment-to-moment behavior. Furthermore, we leveraged recent advances in subcortical imaging and atlasing to lay the groundwork for exploring the contributions of understudied regions in the subcortex. Mind wandering is a complex and heterogeneous phenomenon that interacts with situational factors and defies a unitary neural representation. While singular systems, such as the default mode network (DMN), were not unambiguously related to mind wandering, the dynamic coupling between the DMN and its antagonistic network was identified as essential feature. The integration of information processes in these networks during mind wandering was especially enabled by functional connections of the posterior cingulate cortex (PCC), substantiating its role for regulating internal attention. More subtle connections were also spontaneously echoed in the subcortex, demonstrating functional properties analogous to the PCC. Disentangling the interactions between neuromodulatory influences, behavior, and the functional synergy in cortical and subcortical networks, may reveal qualitatively distinct types off-task thought that remain elusive with experience sampling. These findings emphasize that a comprehensive understanding of how the brain orchestrates mind wandering resides in the harmonics between diverse neural systems.