Role of the Default Mode Network in Cognitive Transitions

Abstract

A frequently repeated finding is that the default mode network (DMN) shows activation decreases during externally focused tasks. This finding has led to an emphasis in DMN research on internally focused self-relevant thought processes. A recent study, in contrast, implicates the DMN in substantial externally focused task switches. Using functional magnetic resonance imaging, we scanned 24 participants performing a task switch experiment. Whilst replicating previous DMN task switch effects, we also found large DMN increases for brief rests as well as task restarts after rest. Our findings are difficult to explain using theories strictly linked to internal or self-directed cognition. In line with principal results from the literature, we suggest that the DMN encodes scene, episode or context, by integrating spatial, self-referential, and temporal information. Context representations are strong at rest, but rereference to context also occurs at major cognitive transitions.

Revealing the neural networks that extract conceptual gestalts from continuously evolving or changing semantic contexts

“…Finally, contrary to what has been suggested by previous investigations (Crittenden et al, 2015;Smith et al, 2018), DMN regions (e.g., precuneus/PCC and mSFG) were not increasingly engaged by shifts of semantic or task contexts. These inconsistencies might be due to substantial differences in the tasks employed in our and other studies.…”

“…To test this hypothesis, we assessed whether the HVN-SLN positive coupling and the HVN-ECN negative coupling were negatively correlated with the behavioral cost of changing task context (operationalized as the difference between NC and HC conditions calculated for both % of missing rates and RTs). Given recent findings (Crittenden et al, 2015;Smith et al, 2018), we also tested whether this correlation could be observed with the HVN-DMN coupling.…”

“…of instructions/rules associated to the task to be performed. Instead, switching between the highly novel tasks employed in previous studies (Crittenden et al, 2015;Smith et al, 2018) necessarily requires this sort of process, given that each stimulus domain (i.e., stimuli depicting people, buildings, words) was associated to two possible classification rules (male/female and old/young for face stimuli; skyscraper/cottage and inside/outside view for building stimuli; first letter and last letter for word stimuli). Hence, the task-switch activity observed in DMN regions in previous studies may reflect the retrieval of task rules, rather than reinstatement and assessment of contextual representations.…”

“…A final and third hypothesis is that the DMN is involved in cognitive transitions by reinstating context-relevant information (Crittenden et al, 2015;Smith et al, 2018). As such one would expect the DMN to be sensitive to a major switch to a new task (NC condition), when a completely different context representation is reawakened.…”

The functional convergence and heterogeneity of social, episodic, and self-referential thought in the default mode network

“…One common proposal is that the DMN represents broad features of a cognitive episode, scene or context (Hassabis and Maguire, 2007;Ranganath and Ritchey, 2012;Manning et al, 2014;Crittenden et al, 2015;Baldassano et al, 2017;Smith et al, 2018). This episode might be imagined, as in spontaneous mind-wandering or recollection of a previous event, or currently perceived (Ranganath and Ritchey, 2012;Manning et al, 2014;Baldassano et al, 2017;Smith et al, 2018). Contextual representations might include spatial, social, temporal, self-related and other features, with reduced processing of these features during focused attention on the details of an external task, but enhancement during spontaneous, self-generated cognition at rest.…”