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  • Visual spatial attention and working memory

    2018-11-15

    Visual-spatial attention and working memory mature across late childhood and adolescence (Westerberg et al., 2004; Zhan et al., 2011). Functional connectivity is a measure believed to reflect the synchrony between dna-pkcs regions (Friston, 1994), and is often calculated as the temporal correlation between pairs of time-series. Changes in functional and structural/white matter connectivity with age are hypothesized to be a key driver of cognitive maturation (Blakemore, 2012; Fair et al., 2007; Rubia, 2013; Supekar et al., 2009; Uddin et al., 2011). In support of this view, protracted development of white matter structure has been observed through early adulthood (Lebel et al., 2008). Age-related variation in fronto-parietal white matter properties across childhood has been linked to increased working memory capacity (Nagy et al., 2004; Østby et al., 2011), and visual-spatial attention (Klarborg et al., 2013). Findings regarding age-effects on fronto-parietal functional connectivity have been mixed. Several developmental neuroimaging studies have shown increased functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent (BOLD) signal during working memory tasks, relative to baseline, in frontal and parietal regions with age-related increases in working memory capacity (Crone et al., 2006; Klingberg et al., 2002; Scherf et al., 2006). Computational modeling has further suggested that fronto-parietal connectivity underlies inter-individual differences in working memory capacity (Edin et al., 2007). In resting-state connectivity studies, although somewhat controversial due to inconsistencies in handling motion artifacts (Power et al., 2012), a general pattern of increasing long-range connectivity with age has been described (Dosenbach et al., 2010; Fair et al., 2007). The spatial pattern of attention networks in children 5–8 years of age has been reported to be fragmented and incomplete compared to the same networks seen in adults (de Bie et al., 2012). In older children, while differences compared to adults in IPS-to-DPLFC connectivity have been observed (Barber et al., 2013), other work has found no difference in fronto-parietal functional connectivity (Jolles et al., 2011; Uddin et al., 2011). Several factors may contribute to variability in findings regarding developmental changes, or age-related variability, in fronto-parietal functional connectivity, including differential sensitivity of task compared resting scans, analysis approach, and small sample size. Among studies that have used region-of-interest (ROI) approaches, choice of seed region may also impact findings, as there is considerable heterogeneity of function and connectivity within both prefrontal (Kahnt et al., 2012; Liu et al., 2013; Moayedi et al., 2014) and parietal (Anderson et al., 2011; Mars et al., 2011; Nelson et al., 2010) cortices. Developmental abnormalities in the IPS have been linked with aberrant numerical and visuospatial cognition (Auzias et al., 2014; Bray et al., 2011; Kesler et al., 2004, 2006; Molko et al., 2003; Nordahl et al., 2007). Therefore, characterizing age-related variability in fronto-parietal functional connectivity is important, both for understanding the neural basis of typical cognitive maturation, and as a baseline for comparing atypical development. The present study investigated age-related variability in IPS functional connectivity across childhood and adolescence, and aimed to circumvent limitations of previous work by (1) using a large database of resting-state fMRI data, and (2) using multiple seeds along the anterior-to-posterior axis of the IPS, in locations corresponding to previously defined IPS0-4 (Swisher et al., 2007) with well characterized patterns of structural connectivity (Bray et al., 2013b; Greenberg et al., 2012; Szczepanski et al., 2013). We hypothesized that IPS sub-regions would show varying functional connectivity with visual and prefrontal regions along the anterior-to-posterior axis, consistent with previous work (Mars et al., 2011). Specifically, we hypothesized that anterior regions of the IPS would be more strongly functionally connected with frontal regions of the network including hFEF, whereas posterior IPS regions would have greater functional connectivity with visual regions. We further hypothesized differential age-related variability in functional connectivity. Specifically, we hypothesized that as primary sensory brain systems have been shown to mature relatively early (Gogtay et al., 2004; Shaw et al., 2008; de Bie et al., 2010), posterior IPS-to-occipital connectivity patterns would be relatively stable, while anterior IPS-to-prefrontal (e.g. DLPFC Barber et al., 2013) connectivity would show a positive association with age.