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    • Finally there are questions concerning cognitive interpretat

    2018-10-29

    Finally, there are questions concerning cognitive interpretations that are routinely assigned to resting-state networks. Because profiles of activity that correlate with the instantiation of cognitive control (i.e., task-based maps of the CCN) appear convergent with maps of the CCN generated from resting state data, it is generally assumed that task-based and resting state methods image identical networks. Direct comparisons however, reveal not only that the topology of the CCN differs across task and rest, but also that task-induced topological features are a stronger predictor of behavior than topology assessed in the absence of an overt task (Dwyer et al., 2014). Whether cognitive interpretations of RSNs, such as the CCN, can be upheld is difficult to say for certain. However, to the extent time course correlations within the CCN are evident in the absence of goal-directed thought (i.e., during sleep and anesthesia), they may be a necessary, but are certainly not a sufficient basis for the instantiation of cognitive control.
    Functional connectivity dynamics
    Conclusions
    Conflict of interest
    Acknowledgments Support for this research was provided by means of grants from the National Science and Engineering Research Council (NSERC), the Canadian Foundation for Innovation (CFI), and the Ontario Innovation Trust to JBM and a Canadian Institute of Health Research (CIHR) postdoctoral fellowship and Brain and Behavior Research Foundation NARSAD Young Investigator Grant to RMH.
    Introduction Working memory (WM) is the ability to maintain representations of recently experienced or recalled information over a short induced pluripotent stem cell of time (Curtis and D’Esposito, 2003). The capacity of working memory in humans is limited (Cowan, 2001; Miller, 1956), and individual differences in capacity are correlated with a variety of cognitive and social outcomes including school performance (Dumontheil and Klingberg, 2012; Finn et al., 2014; Gathercole et al., 2003). Working memory encoding and maintenance without distractors is reliant on the middle frontal gyrus (MFG) and superior parietal cortex, specifically, the intraparietal sulcus (IPS; Todd and Marois, 2004). Recent research has shown that WM filtering ability – the ability to filter extraneous or distracting information from WM during encoding – is strongly associated with overall WM capacity and accuracy (Vogel et al., 2005). Evidence from neuroimaging suggests that the basal ganglia (BG) play an important role in filtering out extraneous information (McNab and Klingberg, 2008). Although a variety of studies have tracked the development of WM and associated neural systems from childhood to early adulthood (Asato et al., 2010; Curtis and D’Esposito, 2003; Lenroot and Giedd, 2006; Sowell et al., 1999, 2004), developmental variation in patterns of neural function that support WM filtering, specifically, remain largely unexplored. Contemporary neurocognitive theories of WM function suggest that, during encoding and maintenance, activity in the MFG reflects a top-down control process that serves to maintain representations of visual stimuli which are processed in the IPS (Curtis and D’Esposito, 2003). Research on WM in humans and other primates has consistently shown activity in the MFG (Goldman-Rakic, 1996) and IPS (Hartley and Speer, 2000; Nelson et al., 2000; Thomas et al., 1999) during tasks where working memory load is manipulated. The MFG and IPS appear to make distinct contributions to WM. Activity in the MFG, but not IPS, is implicated in top-down control over representations in WM (Feredoes et al., 2011; Sakai et al., 2002). Activity in the IPS appears to reflect actual WM storage or maintenance; this idea is supported by several ERP studies which have found that contralateral delay signal over parietal scalp scales with WM load but plateaus when load exceeds the capacity of the subject (McCollough et al., 2007; Vogel and Machizawa, 2004; Vogel et al., 2005). Functional magnetic resonance imaging (fMRI) studies have localized this ‘contralateral delay’ signal to the IPS, such that blood oxygen level dependent (BOLD) signal in the IPS is associated with the number of items being maintained in WM (Todd and Marois, 2004; see also: Xu and Chun, 2006).