(2013)
http://journal.frontiersin.org/article/10.3389/fnhum.2013.00734/full
comment: Ya' know, indirectly, some metaphysical concepts might have to be utilized at some point if we want a better - not a liked word - descriptive model of some...stuff (hard problem of consciousness. What it does and why it emerges in biological systems, that is, beyond the functioning and benefits of network representation of body.) At which point things will...start getting fun.
It's in that reconcile, redefining (limiting) the context and descriptive implications of measurement itself, what is being measured, and the measurer...
The default modes of reading: modulation of posterior cingulate and medial prefrontal cortex connectivity associated with comprehension and task focus while reading
- 1Department of Psychology, University of York, Hesslington, North Yorkshire, UK
- 2Max Planck Research Group: Neuroanatomy & Connectivity, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- 3Department of Social Neuroscience, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- 4Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA, USA
- 5Department of Psychology, Neuroscience and Behavior, McMaster University, Hamilton, ON, Canada
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.
Introduction
The development of writing has profoundly changed our social world: it allows ideas to be publicized to geographically diverse groups of individuals and permits concepts to be passed from generation to generation. More prosaically, but no less importantly, reading is a source of enjoyment available to every literate individual. Despite the value of reading, it can often seem that our minds are ill suited to the task of narrative comprehension. It is relatively common during reading, for example, to experience thoughts and feelings that are unrelated to the prose in front of us. Such task-unrelated thinking occurs across many task contexts (Smallwood and Schooler, 2006) and when it occurs in reading is a well-documented correlate of comprehension problems (Schooler et al., 2004; Smallwood et al., 2008; Franklin et al., 2011; McVay and Kane, 2011). At present we lack a detailed appreciation of the processes that govern how our thoughts are constrained to the narrative of a piece of prose, or those that cause our minds to wander away from what we are reading.
The current study used resting-state functional magnetic resonance imaging (rs-fMRI) to investigate whether variations in the experience of reading across individuals have a basis in the brain’s functional architecture. We were particularly interested in how the reading experience of different individuals varied with the behavior of the anterior medial prefrontal cortex (aMPFC) and posterior cingulate cortex (PCC), two major midline hubs of the default mode network (DMN; Raichle et al., 2001; Greicius and Menon, 2004; Buckner et al., 2008; Andrews-Hanna et al., 2010). The DMN is a constellation of brain regions including regions of prefrontal, parietal and temporal cortex that were initially discovered to “deactivate” during externally driven tasks, and also exhibit correlated intrinsic neural activity. The DMN consists of a midline core that includes the aMPFC and the PCC that can flexibly couple its activity to two additional subsystems: (i) a medial temporal lobe (MTL) subsystem that includes the hippocampus, the medial orbitofrontal cortex, and the temporal poles, and is important in episodic memory; and (ii) a dorsal subsystem that includes a dorsal region of the medial prefrontal cortex and lateral regions of the parietal cortex including the temporoparietal junction, and may be important in simulating of self and other (Buckner et al., 2008; Andrews-Hanna et al., 2010).
Currently the functions of the DMN are a matter of debate: prior studies have documented that the DMN plays a role in task-unrelated thought in sustained attention tasks (Mason et al., 2007;Christoff et al., 2009; Stawarczyk et al., 2011) as well as absent-minded lapses (Eichele et al., 2008; Christoff et al., 2009), suggesting that activity in this network could be responsible for the comprehension deficits that occur when the mind wanders during reading. Given that the DMN is implicated in task-unrelated thinking, it would seem intuitive that this network would be responsible for failures in comprehension that accrue due to mind-wandering.
Despite the appeal of the account of the DMN as the substrate for task-unrelated thought, the picture is likely to be more complicated: regions of the DMN have also been implicated in processes that are likely to be engaged during reading. For example, Fletcher et al. (1995)demonstrated that reading stories containing a narrative relating to either physical reality or to the mental states of other individuals activated the PCC relative to a series of unlinked sentences. Additionally, grey matter volume in the PCC is correlated with an individual’s capacity for phonological decoding (He et al., 2013). Recent meta-analyses have confirmed the role of the PCC and aMPFC in extended narrative comprehension, especially of a fictional nature (Mar, 2011).
Functional studies suggest the DMN is also implicated in processes that readers could use when reading. For example, the DMN is activated when participants make mental state attributions (Spreng et al., 2009; Spreng and Mar, 2012), when they retrieve information from memory (Huijbers et al., 2011), and has been hypothesized to allow for multiple different mental states all of which rely on information from memory to guide behavior (Smallwood et al., 2013). Meta-analyses also indicate that elements of the DMN are important in semantic processing: a capacity which is critical for reading (Binder and Desai, 2011). Semantic processing, mental state attribution, and the retrieval of information from memory are all abilities that are important in narrative comprehension because they allow the reader to understand the motives of characters and to make links between different elements of an extended text.
To understand why the DMN could be implicated in both costs and benefits to reading (Smallwood, 2013), we recorded how effectively individuals stayed on task while they read three different expository texts from an engaging popular work describing the history of science as well as the lives of the protagonists who contributed to this story. Afterwards participants completed a set of open-ended questions assessing their comprehension of what they read. Previously recorded rs-fMRI data was also available from a subset of these individuals which we used to explore how trait differences in the effectiveness of reading, measured both subjectively and objectively, were related to differences in the intrinsic functional connectivity of two of the major hubs of the DMN (aMPFC and PCC).
Based on prior evidence of DMN activation associated both with processes engaged by reading and with mind-wandering, as well as evidence that mind-wandering during reading is associated with poorer reading performance, we predicted that differences in reading effectiveness would relate to distinct patterns of functional connectivity between the midline core of the DMN and other brain regions. Prior studies have looked at how the behavior of resting state networks associated with reading behavior (Koyama et al., 2011), here we report an rs-fMRI investigation that is focused on the DMN. We used hypothesis driven seed-based analysis to examine whether metrics of reading behavior modulate the whole-brain connectivity of these regions. We were particularly interested in whether any observed modulations of functional connectivity could help shed light on how the DMN can be both beneficial and costly to the act of reading. Although this approach is limited by our choice of seed regions, it does not constrain the results of our analysis and so provides a straightforward, hypothesis driven method to assess our question of interest (Cole et al., 2010).
Methods
Healthy participants were recruited for the current experiment from the Max Planck Institute for Human Cognitive and Brain Sciences participant database. Ethical approval was obtained prior to completing this experiment from the Ethics committee of the University of Leipzig (Ref # 360-10-13122010). Participants provided written informed consent prior to their participation.
Assessment of Reading Behavior
Individual differences in maintaining focus on the narrative while reading and subsequent text comprehension was assessed in a sample of 61 healthy native German speakers (age range = 19–50, mean = 27.9 years, (SD = 5) 37 females, all right handed) while they read three excerpts from the official translation of Bill Bryson’s A Short History of Everything, a text that has been used in English language studies of mind-wandering (Smallwood et al., 2009b; Smilek et al., 2010). These texts are engaging non-fiction works that describes the characters and historical contexts of important scientific events. One text dealt with biology, a second with chemistry and a third dealt with geology. On average each text was approximately 1200 words long (mean = 1187). The Fleisch Kincaid levels were calculated using an online website1 and ranged from 34–39 making these texts slightly easier than university level material.
(more at the link above)
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