Mind blanking (MB) is a waking state during which we do not report any mental content. The phenomenology of MB challenges the view of a constantly thinking mind. Here, we comprehensively characterize the MB’s neurobehavioral profile with the aim to delineate its role during ongoing mentation. Using functional MRI experience sampling, we show that the reportability of MB is less frequent, faster, and with lower transitional dynamics than other mental states, pointing to its role as a transient mental relay. Regarding its neural underpinnings, we observed higher global signal amplitude during MB reports, indicating a distinct physiological state. Using the time-varying functional connectome, we show that MB reports can be classified with high accuracy, suggesting that MB has a unique neural composition. Indeed, a pattern of global positive-phase coherence shows the highest similarity to the connectivity patterns associated with MB reports. We interpret this pattern’s rigid signal architecture as hindering content reportability due to the brain’s inability to differentiate signals in an informative way. Collectively, we show that MB has a unique neurobehavioral profile, indicating that nonreportable mental events can happen during wakefulness. Our results add to the characterization of spontaneous mentation and pave the way for more mechanistic investigations of MB’s phenomenology.

Mind-blanking (MB) is the inability to report mental contents, challenging the view of a constantly thought-oriented mind during wakefulness. Using fMRI experience-sampling we show that MB is reported scarcely, fast, and has low transitional dynamics, pointing to its role as a transient mental relay. MB's cerebral profile is linked to an overall positive connectivity pattern, bearing great resemblance to neural configurations observed in local sleeps, possibly reflecting neuronal silencing during wakefulness. We also find less efficient information flow between the default mode (DMN) and other networks before reporting MB. The DMN-salience network segregation was further able to classify MB from other reports in fewer steps, suggestive of an early saliency evaluation of contentless phenomenology along the neurocognitive hierarchy. Collectively, MB's unique neurofunctional profile among thought-oriented reports supports the view of instantaneous mental absences happening during wakefuless, paving the way for more mechanistic investigations of this particular phenomenology during ongoing mentation.

The reportability of spontaneous thinking relies significantly on attention and arousal. As these cognitive faculties change with age, we aimed at testing how spontaneous mental state reportability is influenced accordingly. Using experience sampling, 20 senior (65-75yrs) and 20 young participants (20-30yrs) were prompted to report mind-wandering (MW), mind-blanking (MB), or sensory-related (S) mental states at random times. Attention was assessed with the Attentional Style Questionnaire, and arousal with continuous monitoring of pupil diameter. First, we found more MW occurrences than MB or S across all participants. For young responders, we replicated that MW was more prevalent in easily-distracted participants. In seniors, though, MW was more prevalent in participants with a higher focused attentional style. In senior participants who reported being more easily distracted, MW was associated with lower arousal (pupil constriction) and MB with higher arousal (pupil dilation), reversing the pattern found for young adults and focused seniors. We propose that these effects may result from intentional MW, during which senior participants allocate attentional resources to mentally engage inwards, as opposed to younger participants who get more easily distracted by their own mental activity leading to unintentional MW. Together, our results highlight age-dependent mechanisms by which attentional style and pupil-linked arousal regulate the reportability of spontaneous mental states across age.