Preferential activation of the posterior Default-Mode Network with sequentially predictable task switches

Abstract

The default-mode network (DMN) has been primarily associated with internally-directed and self-relevant cognition. This perspective is expanding to recognise its importance in executive behaviours like switching. We investigated the effect different task-switching manipulations have on DMN activation in two studies with novel fMRI paradigms. In the first study, the paradigm manipulated visual discriminability, visuo-perceptual distance and sequential predictability during switching. Increased posterior cingulate/precuneus (PCC/PrCC) activity was evident during switching; critically, this was strongest when the occurrence of the switch was predictable. In the second study, we sought to replicate and further investigate this switch-related effect with a fully factorial design manipulating sequential, spatial and visual-feature predictability. Whole-brain analysis again identified a PCC/PrCC-centred cluster that was more active for sequentially predictable versus unpredictable switches, but not for the other predictability dimensions. We propose PCC/PrCC DMN subregions may play a prominent executive role in mapping the sequential structure of complex tasks.

Prefrontal tDCS is unable to modulate mind wandering propensity or underlying functional or effective brain connectivity

“…Therefore, the excitatory coupling from the PCC to the MPFC in conjunction with the inhibitory coupling from the PCC to both ECN and SN may signify the PCC acting as a switch between internally and externally directed thoughts. This again supports research indicating the PCC is a major hub between networks 86 – 88 , particularly regarding task switching 94 . This may also help explain the inconsistent results previously mentioned regarding the role of the PCC at rest and during tasks, as if the role of the PCC is to shift between internally and externally directed thoughts, its coupling with each network will differ depending on the task at hand.…”

Dissociations between glucose metabolism and blood oxygenation in the human default mode network revealed by simultaneous PET-fMRI

“…Specifically, the BOLD time-series in posterior precuneus exhibited a task transition-related increase followed by a sustained response resembling the NBR in adjacent posterior cingulate. Activity related to a shift in context has been observed previously for regions belonging to the DMN in both humans (17,(55)(56)(57) and macaques (34,35). Finally, we also observed heterogeneity of FDG signal changes within the areas of the NBR in MPFC, with a small cluster in frontal pole showing FDG decreases during task and aligning with BOLD here.…”

DLPFC-tDCS unable to modulate mind-wandering propensity nor underlying functional or effective brain connectivity

“…Therefore, the excitatory coupling from the PCC to the MPFC in conjunction with the inhibitory coupling from the PCC to both ECN and SN may signify the PCC acting as a switch between internally and externally directed thoughts. This again supports research indicating the PCC is a major hub between networks 75–77 , particularly regarding task switching 83 . This may also help explain the inconsistent results previously mentioned regarding the role of the PCC at rest and during tasks, as if the role of the PCC is to shift between internally and externally directed thoughts, its coupling with each network will differ depending on the task at hand.…”