Dynamic reconfiguration of the default mode network during narrative comprehension

Abstract

Does the default mode network (DMN) reconfigure to encode information about the changing environment? This question has proven difficult, because patterns of functional connectivity reflect a mixture of stimulus-induced neural processes, intrinsic neural processes and non-neuronal noise. Here we introduce inter-subject functional correlation (ISFC), which isolates stimulus-dependent inter-regional correlations between brains exposed to the same stimulus. During fMRI, we had subjects listen to a real-life auditory narrative and to temporally scrambled versions of the narrative. We used ISFC to isolate correlation patterns within the DMN that were locked to the processing of each narrative segment and specific to its meaning within the narrative context. The momentary configurations of DMN ISFC were highly replicable across groups. Moreover, DMN coupling strength predicted memory of narrative segments. Thus, ISFC opens new avenues for linking brain network dynamics to stimulus features and behaviour.

Spontaneous default network activity reflects behavioral variability independent of mind-wandering

“…For example, although the DMN is commonly deactivated during externally oriented tasks requiring cognitive control (15), older adult populations report low levels of mind-wandering during task performance yet exhibit attenuated DMN deactivation (16). Additionally, in certain contexts, increased DMN activity is time-locked to stimulus changes in the external environment (17,18).Although spontaneous increases of DMN activity are postulated to reflect mind-wandering, a highly consistent finding is that DMN activity is higher when ongoing behavior is stable rather than variable (19-21). This finding would be counterintuitive if there were a one-to-one mapping between mind-wandering intensity and DMN activity.…”

“…Second, intracranial electrophysiology studies of DMN areas have shown increased activity immediately at the offset of task performance, perhaps too rapidly to reflect mind-wandering (49). Third, fMRI studies with unique task paradigms suggest that under certain contexts, increased DMN activity occurs during cognitive processes that may involve aspects of externally oriented attention (17,18,50). Finally, studies of spontaneous prestimulus activity suggest nuanced relationships of DMN activity with attentional performance (51,52).…”

“…For example, although the DMN is commonly deactivated during externally oriented tasks requiring cognitive control (15), older adult populations report low levels of mind-wandering during task performance yet exhibit attenuated DMN deactivation (16). Additionally, in certain contexts, increased DMN activity is time-locked to stimulus changes in the external environment (17,18).…”

Decoding the Neural Representation of Story Meanings across Languages

“…A series of studies have shown that the DMN seems to be involved in representing the global meaning of passages, rather than meaning at the word or sentence-level (Ferstl, Neumann, Bogler, & Von Cramon, 2008;Lerner et al, 2011). Further, the activity in the DMN is consistent when a story is presented in different modalities (spoken vs. written), or in different languages (Russian vs. English to native speakers of these languages), indicating highly abstracted representations of the stimuli in this network (Chen et al, 2016;Honey, Thompson, Lerner, & Hasson, 2012;Regev, Honey, Simony, & Hasson, 2013). The word-level semantic map produced by Huth et al (2016) also demonstrates significant overlap with the DMN.…”

“…The word-level semantic map produced by Huth et al (2016) also demonstrates significant overlap with the DMN. More recently, Simony et al (2016) show that the DMN reconfigures consistently across subjects when processing narrative stimuli. Also, a recent study demonstrates that patterns of activity in the DMN when people are describing a narrative are highly consistent across individuals and specific to events in the narrative (Chen et al, 2016).…”