Differential contributions of default and dorsal attention networks to remembering thoughts and external stimuli from real-life events

Episodic memories are typically composed of perceptual information derived from the external environment and representations of internal states (e.g., one’s thoughts during prior episodes). To date, however, research has mostly focused on the remembrance of external stimuli, such that little is known about how internal mentation is represented within episodic memory. In the present fMRI study, we examined the neural correlates of these two components of episodic memories using a novel method of cuing memories from photographs taken during real-life events. We found that, compared to corresponding semantic memory tasks, memories for internal thoughts and external elements were associated with activity in brain areas supporting episodic recollection. Most importantly, however, the two kinds of memories also showed differential activation in large-scale brain networks: the remembrance of external elements was associated with greater activity in the dorsal attention network, whereas memories of internal thoughts mainly recruited default network areas. These findings shed new light on the representation of internal and external aspects of prior experience within episodic memory. The default network may contribute to the reinstatement of thoughts experienced during past events, whereas the dorsal attention network may support the allocation of attention to visuo-spatial features within episodic memory representations

Representational dynamics of memories for real-life events

peer reviewedThe continuous flow of experience that characterizes real-life events is not recorded as such in episodic memory but is condensed as a succession of event segments separated by temporal discontinuities. To unravel the neural basis of this representational structure, we recorded real-life events using wearable camera technology and used fMRI to investigate brain activity during their temporal unfolding in memory. We found that, compared to the representation of static scenes in memory, dynamically unfolding memory representations were associated with greater activation of the posterior medial episodic network. Strikingly, by analyzing the autocorrelation of brain activity patterns at successive time points throughout the retrieval period, we found that this network showed higher temporal dynamics when recalling events that included a higher density of event segments. These results reveal the key role of the posterior medial network in representing the dynamic unfolding of the event segments that constitute real-world memories

Understanding Everyday Events: Predictive Looking Errors Drive Memory Updating

peer reviewedMemory-guided predictions can improve event comprehension by guiding attention and the eyes to the location where an actor is about to perform an action. But when events change, viewers may experience predictive looking errors and need to update their memories. In two experiments (Ns = 38 and 111), we examined the consequences of mnemonic predictive looking errors for comprehending and remembering event changes. University students watched movies of everyday activities with actions that repeated exactly and actions that repeated with changed features—for example, an actor reached for a paper towel on one occasion and a dish towel on the next. Memory guidance led to predictive looking errors that were associated with better memory for subsequently changed event features. These results indicate that retrieving recent event features can guide predictions during unfolding events, and that error signals derived from mismatches between mnemonic predictions and actual events contribute to new learning.Mind-wandering in everyday event comprehension: Memory, attention, and the brai

Attention Supports Verbal Short-Term Memory via Competition between Dorsal and Ventral Attention Networks

Interactions between the neural correlates of short-term memory (STM) and attention have been actively studied in the visual STM domain but much less in the verbal STM domain. Here we show that the same attention mechanisms that have been shown to shape the neural networks of visual STM also shape those of verbal STM. Based on previous research in visual STM, we contrasted the involvement of a dorsal attention network centered on the intraparietal sulcus supporting task-related attention and a ventral attention network centered on the temporoparietal junction supporting stimulus-related attention. We observed that, with increasing STM load, the dorsal attention network was activated while the ventral attention network was deactivated, especially during early maintenance. Importantly, activation in the ventral attention network increased in response to task-irrelevant stimuli briefly presented during the maintenance phase of the STM trials but only during low-load STM conditions, which were associated with the lowest levels of activity in the dorsal attention network during encoding and early maintenance. By demonstrating a trade-off between task-related and stimulus-related attention networks during verbal STM, this study highlights the dynamics of attentional processes involved in verbal ST

Neural Correlates of Ongoing Conscious Experience: Both Task-Unrelatedness and Stimulus-Independence Are Related to Default Network Activity

The default mode network (DMN) is a set of brain regions that consistently shows higher activity at rest compared to tasks requiring sustained focused attention toward externally presented stimuli. The cognitive processes that the DMN possibly underlies remain a matter of debate. It has alternately been proposed that DMN activity reflects unfocused attention toward external stimuli or the occurrence of internally generated thoughts. The present study aimed at clarifying this issue by investigating the neural correlates of the various kinds of conscious experiences that can occur during task performance. Four classes of conscious experiences (i.e., being fully focused on the task, distractions by irrelevant sensations/perceptions, interfering thoughts related to the appraisal of the task, and mind-wandering) that varied along two dimensions (“task-relatedness” and “stimulus-dependency”) were sampled using thought-probes while the participants performed a go/no-go task. Analyses performed on the intervals preceding each probe according to the reported subjective experience revealed that both dimensions are relevant to explain activity in several regions of the DMN, namely the medial prefrontal cortex, posterior cingulate cortex/precuneus, and posterior inferior parietal lobe. Notably, an additive effect of the two dimensions was demonstrated for midline DMN regions. On the other hand, lateral temporal regions (also part of the DMN) were specifically related to stimulus-independent reports. These results suggest that midline DMN regions underlie cognitive processes that are active during both internal thoughts and external unfocused attention. They also strengthen the view that the DMN can be fractionated into different subcomponents and reveal the necessity to consider both the stimulus-dependent and the task-related dimensions of conscious experiences when studying the possible functional roles of the DMN

Conjoint influence of mind-wandering and sleepiness on task performance

Recent research suggests that sleepiness and mind-wandering—the experience of thoughts that are both stimulus-independent and task-unrelated—frequently co-occur and are both associated with poorer cognitive functioning. Whether these two phenomena have distinguishable effects on task performance remains unknown, however. To investigate this question, we employed the online experience sampling of mind-wandering episodes and subjective sleepiness during a laboratory task (the Sustained Attention to Response Task; SART), and also assessed mind-wandering frequency and sleep-related disturbances in daily life using self-report questionnaires. The results revealed that the tendency to experience mind-wandering episodes during the SART and daily life was associated with higher levels of daytime sleepiness and sleep-related disturbances. Importantly, however, mind-wandering and sleepiness were independent predictors of SART performance at both the within- and between-individuals levels. These findings demonstrate that, although mind-wandering and sleepiness frequently co-occur, these two phenomena have distinguishable and additive effects on task performance

Neural correlates of personal goal processing during episodic future thinking and mind-wandering: an ALE meta-analysis

The ability to imagine the future is a complex mental faculty that depends on an ensemble of cognitive processes supported by an extended set of brain regions. Our aim here was to shed light on one key component of future thinking—personal goal processing—and to determine its neural correlates during both directed and spontaneous forms of thoughts. To address this question, we performed separate ALE meta-analyses of neuroimaging studies of episodic future thinking, mind-wandering, and personal goal processing, and then investigated the commonalities and differences in brain activity between these three domains. The results showed that the three domains activated a common set of brain regions within the default network and, most notably, the medial prefrontal cortex. This finding suggests that the medial prefrontal cortex mediates the processing of personal goals during both episodic future thinking and mind-wandering. Differences in activation were also observed, and notably regions supporting cognitive control processes (the dorsolateral prefrontal cortex) were recruited to a lesser extent during mind-wandering than experimentally directed future thinking, suggesting that different kinds of self-generated thoughts may recruit varying levels of attentional control abilities

Phenomenology of future-oriented mind-wandering episodes

Recent research suggests that prospective and non-prospective forms of mind-wandering possess distinct properties, yet little is known about what exactly differentiates between future-oriented and non-future-oriented mind-wandering episodes. In the present study, we used multilevel exploratory factor analyses to examine the factorial structure of various phenomenological dimensions of mind-wandering, and we then investigated whether future-oriented mind-wandering episodes differ from other classes of mind-wandering along the identified factors. We found that the phenomenological dimensions of mind-wandering are structured in four factors: representational format (inner speech vs. visual imagery), personal relevance, realism/concreteness, and structuration. Prospective mind-wandering differed from non-prospective mind-wandering along each of these factors. Specifically, future-oriented mind-wandering episodes involved inner speech to a greater extent, were more personally relevant, more realistic/concrete, and more often part of structured sequences of thoughts. These results show that future-oriented mind-wandering possesses a unique phenomenological signature and provide new insights into how this particular form of mind-wandering may adaptively contribute to autobiographical planning