Where was my mind? Neurophysiological correlates of mind blanking

Human experience is rich and contentful. At any moment, our thoughts encompass many
perceptions, beliefs, emotions, and feelings. Yet, the notion of a contentful mind does not
fully capture our experience. Recent paradigms of spontaneous thinking reveal that people sometimes fail to report content or have nothing to report. This experience, termed mind-blanking (MB), contrasts with the assumption that the mind is always filled with content and raises the question: Why does introspection sometimes yield nothing? Neuroscientific research suggests that MB occurs during reduced cortical arousal. Aligning with this view, the present thesis seeks to deepen our understanding of MB by examining how arousal extends beyond cortical correlates to include bodily physiology, highlighting its role in facilitating MB reports.
Specifically, we used a cohort of neurophysiological modalities under different experimental settings to relate MB to an underlying brain-body structure. In Study 1, we examined cortical activity preceding MB reports to identify brain regions engaged when individuals are unable to report their thoughts at rest. In Study 2, we combined experience sampling under different arousal conditions with concomitant brain-body measurements to correlate the frequency of MB reports with different brain-body states. Finally, in Study 3, we examined fMRI-EEG activity during a sustained attention-to-response task to differentiate the neuronal correlates of MB and low arousal and understand the electrophysiological origins of these neuronal correlates.
In summary, we demonstrate that MB is associated with BOLD deactivations spanning the
whole brain. Compared to mental states with reportable content, we observed deactivations in frontal and parietal areas. Furthermore, we show that MB is an arousal-mediated mental state, with its occurrence increasing during altered arousal levels. While MB could be decoded from body activity alone, optimal decoding requires both brain and body activity. Lastly, we show that alertness and mental states are neuronally dissociable. In the General Discussion, I outline a roadmap for MB research, focusing on a) exploring the phenomenology of “no thought” and b) creating a psychological model of MB. Taken together, this thesis bridges brain and body rhythms with self-reported experience to reveal moments at the boundaries of consciousness, where being awake does not necessarily translate into conscious thought.