Task‐related changes in degree centrality and local coherence of the posterior cingulate cortex after major cardiac surgery in older adults

Abstract Objectives Older adults often display postoperative cognitive decline (POCD) after surgery, yet it is unclear to what extent functional connectivity (FC) alterations may underlie these deficits. We examined for postoperative voxel‐wise FC changes in response to increased working memory load demands in cardiac surgery patients and nonsurgical controls. Experimental design Older cardiac surgery patients ( n = 25) completed a verbal N‐back working memory task during MRI scanning and cognitive testing before and 6 weeks after surgery; nonsurgical controls with cardiac disease ( n = 26) underwent these assessments at identical time intervals. We measured postoperative changes in degree centrality, the number of edges attached to a brain node, and local coherence, the temporal homogeneity of regional functional correlations, using voxel‐wise graph theory‐based FC metrics. Group × time differences were evaluated in these FC metrics associated with increased N‐back working memory load (2‐back > 1‐back), using a two‐stage partitioned variance, mixed ANCOVA. Principal observations Cardiac surgery patients demonstrated postoperative working memory load‐related degree centrality increases in the left dorsal posterior cingulate cortex (dPCC; p < .001, cluster p ‐FWE < .05). The dPCC also showed a postoperative increase in working memory load‐associated local coherence ( p < .001, cluster p ‐FWE < .05). dPCC degree centrality and local coherence increases were inversely associated with global cognitive change in surgery patients ( p < .01), but not in controls. Conclusions Cardiac surgery patients showed postoperative increases in working memory load‐associated degree centrality and local coherence of the dPCC that were inversely associated with postoperative global cognitive outcomes and independent of perioperative cerebrovascular damage.