The neural factors that account for the visual processing-speed reduction in aging are incompletely understood. Based on previous reports of age-related decreases in the intrinsic functional connectivity (iFC) within the cingulo-opercular network and its relevance for processing speed, we hypothesized that these decreases are associated with age-related reductions in visual processing speed. We used a whole-report task and modeling based on Bundesen's 'theory of visual attention' to parameterize visual processing speed in 91 healthy participants from 20 to 77 years old. iFC was estimated using independent-component analysis of resting-state fMRI data. From the clusters within the cingulo-opercular network exhibiting age-related decreased iFC, we found a cluster in the left insula to be particularly associated with visual processing speed and to mediate the age effect on visual speed. This mediation was not observed for age-related decreased iFC in other networks or for other attentional parameters. Our results point to the iFC in the cingulo-opercular network, represented by the left insula, as being a relevant marker for visual processing-speed changes in aging.Next, we performed two lines of control analysis. First, we checked whether the association between the cingulo-opercular network and visual processing speed is a specific one, as hypothesized, rather than being part of a more global relationship between changes in iFC and visual attention functions in general. That is, given the well-documented age-related decreases in iFC in the default-mode and dorsal-attention networks (see, e.g., Andrews-Hanna et al., 2007;Damoiseaux et al., 2008;Ferreira and Busatto, 2013), age-related reductions in visual processing speed might conceivably be associated with a general age-related decrease of iFC, rather than with that of the cingulo-opercular network exclusively. To check for this, (a) we examined whether visual processing speed C also relates to the iFC in other networks; and (b) we assessed whether the iFC in the cingulo-opercular network relates to other visual attention functions previously reported to change with aging, such as the visual perceptual threshold and VSTM storage capacity (see, e.g., McAvinue et al., 2012).Second, we controlled for potentially relevant confounds in the association between iFC in the cingulo-opercular network and visual processing speed. In particular, given that iFC in the cinguloopercular network has previously been found to be related to anxiety (see, e.g., Seeley et al., 2007) and anxiety level might in turn affect processing speed, we controlled for anxiety using the state-trait anxiety inventory (STAI;Laux et al., 1981;Spielberger et al., 1970). Two other potential confounds
