Distinct cortical profiles underlie the common reportability of thought-free experiences

Mind blanking (MB) is a mental state of seemingly no reportable thought content. The question of how we can entertain no thoughts while awake is challenging for the study of spontaneous thinking. By combining EEG-fMRI with experience sampling during task performance, we categorised changes in mental content and self-reported vigilance to map the neurophysiological signatures of MB. We demonstrate that fMRI connectivity around MB reports is characterised by a "rich" pattern of long and short-range signal anticorrelations. At the same time, sleepiness reports are linked to a "simpler" hyperconnected fMRI pattern, characterised by overall positive connectivity. Put together, an interaction appears: when people report being alert, connectomes around MB reports resemble the hyperconnected pattern, indicating that the neuronal correlates of MB depend on self-rated vigilance. The hyperconnected pattern also correlated with EEG slow-wave activity, tying MBs topology to sleep-like electrophysiology during wakefulness. Collectively, we show that distinct cortical events underlie the shared phenomenology of a thought-free mind. We conclude that MBs neurophysiological correlates vary across perceived vigilance levels and that more refined characterisation of the neuronal correlates of thought-less mental states exist. Our findings build on the quest to bridge mental content and its absence with measurable brain activity and provide insights into how ongoing thinking is maintained during wakefulness.