Mind blanking is a distinct mental state linked to a recurrent brain profile of globally positive connectivity during ongoing mentation

Abstract

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.

Keywords: experience sampling; functional connectivity; mental content; mind blanking; resting state.

Fig. 1.

Data acquisition and analysis paradigm. While at rest, participants were randomly interrupted by an auditory probe to report their immediate mental state choosing between absence (MB), Sens, SDep, and SInd. In order to estimate which brain configuration corresponded to a reported mental state, connectivity matrices were estimated via phase-based coherence for each fMRI volume. The matrices were then organized in distinct patterns via k-means clustering, and the similarity between these patterns and the matrices relating to the reported mental states of the preprobe period was calculated. The pattern with the highest similarity to the preprobe matrices was assigned to that reported mental state.

Fig. 2.

Mind Blanking (MB) is characterized by a distinct behavioral profile. (A) MB shows significantly low reportability by comparison to the other mental states, replicating past findings (FDR P < 0.05). (B) MB is reported significantly faster than SDep and SInd mental states, possibly reflecting shorter cognitive evaluation due to the “absent content” as opposed to thought-related reports. (C) The Markov model shows that the probability of reporting an MB state after exploring other mental states is low but equal (6%), suggesting that MB might serve as a transient mental relay during spontaneous mentation. Sens, sensory perception of stimuli; SDep, stimulus-dependent thoughts; SInd, stimulus-indepedent thoughts.

Fig. 3.

Volumes labeled as Mind Blanking (MB) are characterized by high global signal (GS) amplitude. The average absolute value of the GS shows that the GS amplitude is significantly higher for volumes reportes as MB compared to the GS amplitude observed in volumes reporting content-oriented states, pointing to a distinct physiological substrate supporting MB reportability. Bars show the mean absolute value, and error bars show 95% CIs. Sens, sensory perception of stimuli; SDep, stimulus-dependent thoughts; SInd, stimulus-indepedent thoughts.

Fig. 4.

MB is associated with an overall positive interregional brain connectivity pattern. (A) Brain functional organization during rest can be summarized into four main connectivity patterns of complex cortical interactions (pattern 1 [P1]), visual network anticorrelations (pattern 2 [P2]), globally positive coherence (pattern 3 [P3]), and low interareal connectivity (pattern 4 [P4]). There were similar occurrences rates across patterns, except for P4, which potentially reflects the underlying anatomy and therefore acts as a foundation upon which the others can occur. (B) The globally positive phase coherence P3 shows the highest similarity (positive contrast value of cosine similarity) to the connectivity matrices related to the MB reports compared to the other mental states. Black dots show the difference between similarity measures to the related connectivity pattern for each pair of mental states; error bars indicate 95% CIs; vertical blue lines indicate the zero differences. Conn, connectivity (phase-based coherence); DMN, default mode network; Cont, executive control network; DA, dorsal attentional network; VA, ventral attentional network; Lm, limbic network; Vis, visual network; SM, somatomotor network.