The default modes of reading: modulation of posterior cingulate and medial prefrontal cortex connectivity associated with comprehension and task focus while reading

Abstract

Reading is a fundamental human capacity and yet it can easily be derailed by the simple act of mind-wandering. A large-scale brain network, referred to as the default mode network (DMN), has been shown to be involved in both mind-wandering and reading, raising the question as to how the same neural system could be implicated in processes with both costs and benefits to narrative comprehension. Resting-state functional magnetic resonance imaging (rs-fMRI) was used to explore whether the intrinsic functional connectivity of the two key midline hubs of the DMN—the posterior cingulate cortex (PCC) and anterior medial prefrontal cortex (aMPFC)—was predictive of individual differences in reading comprehension and task focus recorded outside of the scanner. Worse comprehension was associated with greater functional connectivity between the PCC and a region of the ventral striatum. Better comprehension was associated with greater functional connectivity with a region of the right insula. By contrast reports of increasing task focus were associated with functional connectivity from the aMPFC to clusters in the PCC, the left parietal and temporal cortex, and the cerebellum. Our results suggest that the DMN has both costs (such as poor comprehension) and benefits to reading (such as an on-task focus) because its midline core can couple its activity with other regions to form distinct functional communities that allow seemingly opposing mental states to occur. This flexible coupling allows the DMN to participate in cognitive states that complement the act of reading as well as others that do not.

An individual differences analysis of the neurocognitive architecture of the semantic system at rest

“…Alternatively, some participants may have had difficulty constraining their attention to the task in hand, a state that is known to impact negatively on task performance (for a review see Smallwood & Schooler, 2015). This latter hypothesis is supported by the observation that the DMN (Buckner et al, 2008, Raichle et al, 2001) has an antagonistic relationship to executive regions (Fox & Raichle, 2007) and can derail task performance when activity occurs under inappropriate conditions (Smallwood et al, 2013, Weissman et al, 2006). There was a link between poor performance and stronger connectivity between language/semantic and default mode regions in several independent models (e.g., for letter fluency from pIFG, and high frequency words from aSTG): when the regions associated with poorer performance in these analyses were seeded in an independent data set, they showed common areas of functional connectivity in default mode and limbic cortex, most clearly in ventromedial PFC.…”

“…These latter results are difficult to interpret because the cluster map crosses anatomical boundaries that are not directly linked (e.g. there are no direct links between primary visual cortex and the cerebellum, see also Smallwood et al, 2013 for a similar issue). For this reason, we won’t include them in the discussion but we made the unthresholded maps of these results publicly available on Neurovault (Table 5).…”

“…Nevertheless, these findings do not contradict the view that, under some circumstances, greater engagement of regions within the DMN (e.g., regions in ATL that fall within this network) may show a positive relationship with semantic performance. It may be the specific nature of network-network coupling combined with the specific task demands that determine the consequence for behaviour (see also Smallwood et al, 2013). …”

Mind-Wandering With and Without Intention

“…Research on mind-wandering has seen a massive increase in recent years, spreading to a wide variety of psychological domains including those examining cognition [1–10], neuroscience [11–16], education [17–20], creativity [21,22], clinical populations [23–26], and workplace functioning [27], to name a few. The rapidly growing body of research on mind-wandering was largely stimulated by Smallwood and Schooler’s [28] integrative review of related concepts such as ‘task-unrelated imagery and thoughts (TUITs)’ [29] and ‘stimulus-independent thought’ [30].…”

Maintenance and Representation of Mind Wandering during Resting-State fMRI

“…Alternatively, mind-wandering has been assessed using experience or thought sampling in conjunction with resting-state fMRI scanning151617181920. While regions within the default mode network are involved in mind-wandering, a number of other brain regions outside the default mode network also show associations with various contents and forms of spontaneous thoughts1015162122. These findings contribute to an increasingly diverse and complex understanding of the spontaneous thoughts that may occur during resting-state fMRI scans, and thus provoke more questions on the impact of mind-wandering on fMRI data.…”