Mind-wandering Is Accompanied by Both Local Sleep and Enhanced Processes of Spatial Attention Allocation

Mind Wandering during Implicit Learning Is Associated with Increased Periodic EEG Activity and Improved Extraction of Hidden Probabilistic Patterns

Mind wandering, occupying 30-50% of our waking time, remains an enigmatic phenomenon in cognitive neuroscience. A large number of studies showed a negative association between mind wandering and attention-demanding (model-based) tasks in both natural settings and laboratory conditions. Mind wandering, however, does not seem to be detrimental for all cognitive domains and was observed to benefit creativity and problem-solving. We examined if mind wandering may facilitate model-free processes, such as probabilistic learning, which relies on the automatic acquisition of statistical regularities with minimal attentional demands. We administered a well-established implicit probabilistic learning task combined with thought probes in healthy adults (N = 37, 30 females). To explore the neural correlates of mind wandering and probabilistic learning, participants were fitted with high-density electroencephalography. Our findings indicate that probabilistic learning was not only immune to periods of mind wandering but was positively associated with it. Spontaneous, as opposed to deliberate mind wandering, was particularly beneficial for extracting the probabilistic patterns hidden in the visual stream. Cortical oscillatory activity in the low-frequency (slow and delta) range, indicative of covert sleep-like states, was associated with both mind wandering and improved probabilistic learning, particularly in the early stages of the task. Given the importance of probabilistic implicit learning in predictive processing, our findings provide novel insights into the potential cognitive benefits of task-unrelated thoughts in addition to shedding light on its neural mechanisms.

Mind wandering enhances statistical learning

The human brain spends 30-50% of its waking hours engaged in mind-wandering (MW), a common phenomenon in which individuals either spontaneously or deliberately shift their attention away from external tasks to task-unrelated internal thoughts. Despite the significant amount of time dedicated to MW, its underlying reasons remain unexplained. Our pre-registered study investigates the potential adaptive aspects of MW, particularly its role in predictive processes measured by statistical learning. We simultaneously assessed visuomotor task performance as well as the capability to extract probabilistic information from the environment while assessing task focus (on-task vs. MW). We found that MW was associated with enhanced extraction of hidden, but predictable patterns. This finding suggests that MW may have functional relevance in human cognition by shaping behavior and predictive processes. Overall, our results highlight the importance of considering the adaptive aspects of MW, and its potential to enhance certain fundamental cognitive abilities.

Differential contributions of the C1 ERP and broadband high-frequency activity to visual processing

The high-frequency activity (HFA; 80-150 Hz) in human intracranial recordings shows a differential modulation to different degrees in contrast when stimuli are behaviorally relevant, indicating a feedforward process. However, the HFA is also significantly dominated by superficial layers and exhibits a peak before 200 ms, suggesting that it is more likely a feedback signal. Magnetoencephalographic (MEG) recordings are suited to reveal an HFA modulation similar to its modulation in intracranial recordings. This allows for noninvasive, direct comparison of HFA with the C1, an established measure for feedforward input to V1, to test whether HFA represents feedforward or rather feedback. In simultaneous recordings, we used the EEG-C1 event-related potential (ERP) component and MEG-HFA to define feedforward processing in visual cortices. C1 latency preceded the HFA peak modulation, which had a more sustained response. Furthermore, modulation parameters like onset, peak time, and peak amplitude were uncorrelated. Most importantly, the C1 but not HFA distinguished small task-irrelevant contrast differences in visual stimulation. These results highlight the differential roles for the C1 and HFA in visual processing with the C1 measuring feedforward discrimination ability and HFA indexing feedforward and feedback processing.NEW & NOTEWORTHY Whether the broadband high-frequency activity (HFA) represents exclusively feedforward or feedback processing remains unclear. In this study, we compared the response characteristics of the HFA-magnetoencephalographic (MEG) and the C1-EEG component to systematic contrast modulations of task-irrelevant visual stimulation. Our findings reveal that the more sustained HFA follows the C1 component and, unlike the C1, is not modulated by task-irrelevant contrast differences. This timing of the HFA modulation suggests that HFA encompasses both feedforward and feedback processing.

Reduced REM and N2 sleep, and lower dream intensity predict increased mind-wandering

Mind-wandering is a mental state in which attention shifts from the present environment or current task to internally driven, self-referent mental content. Homeostatic sleep pressure seems to facilitate mind-wandering as indicated by studies observing links between increased mind-wandering and impaired sleep. Nevertheless, previous studies mostly relied on cross-sectional measurements and self-reports. We aimed to combine the accuracy of objective sleep measures with the use of self-reports in a naturalistic setting in order to examine if objective sleep parameters predict the tendency for increased mind-wandering on the following day. We used mobile sleep electroencephalographic (EEG) headbands and self-report scales over 7 consecutive nights in a group of 67 healthy participants yielding ~400 analyzable nights. Nights with more wakefulness and shorter REM and slow wave sleep were associated with poorer subjective sleep quality at the intraindividual level. Reduced REM and N2 sleep, as well as less intense dream experiences, predicted more mind-wandering the following day. Our micro-longitudinal study indicates that intraindividual fluctuations in the duration of specific sleep stages predict the perception of sleep quality as assessed in the morning, as well as the intensity of daytime mind-wandering the following hours. The combined application of sleep EEG assessments and self-reports over repeated assessments provides new insights into the subtle intraindividual, night-to-day associations between nighttime sleep and the next day's subjective experiences.

Total sleep deprivation impairs visual selective attention and triggers a compensatory effect: evidence from event-related potentials

Many studies have demonstrated the impairment of sustained attention due to total sleep deprivation (TSD). However, it remains unclear whether and how TSD affects the processing of visual selective attention. In the current study, 24 volunteers performed a visual search task before and after TSD over a period of 36 h while undergoing spontaneous electroencephalography. Paired-sample t-tests of behavioral performance revealed that, compared with baseline values, the participants showed lower accuracy and higher variance in response time in visual search tasks performed after TSD. Analysis of the event-related potentials (ERPs) showed that the mean amplitude of the N2-posterior-contralateral (N2pc) difference wave after TSD was less negative than that at baseline and the mean amplitude of P3 after TSD was more positive than that at baseline. Our findings suggest that TSD significantly attenuates attentional direction/orientation processing and triggers a compensatory effect in the parietal brain to partially offset the impairments. These findings provide new evidence and improve our understanding of the effects of sleep loss.

The concurrent and longitudinal impact of sleep on mind wandering in early adolescents

Mind wandering refers to task-unrelated thoughts that can interfere with ongoing tasks and could be sleep-driven across childhood. The present study investigated the mechanisms of the association between early adolescents' sleep and mind wandering with emotional symptoms and executive function as potential mediators. A total of 257 early adolescents (baseline aged 9-13 years old; 131 boys) completed the questionnaires consisting of the Pittsburgh Sleep Quality Index, mind wandering, depression and anxiety symptoms, and executive function. Cross-sectional and longitudinal data revealed a sequential mediation pathway of emotional symptoms and executive function in the association between sleep and mind wandering. The mediating effect of emotional symptoms in the link between sleep quality and mind wandering was significant among boys but not girls.