<p>Short- and long-lag contributions to ACF-sum intrinsic timescale.</p>

<p>To examine whether ACF-sum intrinsic timescale was differentially driven by short- versus longer-lag autocorrelation structure, we decomposed the positive ACF area into short-lag and long-lag components. <b>(a)</b> The short-lag component was modestly associated with the intrinsic timescale estimated using the original ACF-sum method. The regional age effects from the short-lag component were moderately associated with age effects from the original method. <b>(b)</b> In contrast, the short-lag component was highly associated with lag-1 temporal autocorrelation (lag-1 TA), both for regional timescale maps and regional age effects. <b>(c)</b> The long-lag component and its age effects were strongly associated with the original findings estimated using the ACF-sum method. <b>(d)</b> In contrast, the long-lag component was not significantly associated with lag-1 TA in regional timescale maps and was only weakly associated with lag-1 TA regional age effects.

Each data point in the scatter plot represents a brain region from the Schaefer 400 atlas. The data points are colored based on their rankings on the S–A axis. <i>r</i>_s denotes Spearman’s rank correlation coefficient. Significance was assessed using 10,000 spin tests.