Posterior cortical atrophy: reorganization of the dorsal attention network and its implications on volume loss and clinical performance

Posterior cortical atrophy (PCA) is associated with visual attention, episodic memory, and working memory deficits, in addition to the typical visual dysfunction. The dorsal attention network (DAN) plays a critical role in modulating these functions. However, little is known about the relationship of DAN with other core networks (visual and default mode networks (DMN)) and its relationships to volume loss and memory function in PCA. Fifty-seven PCA patients were compared to 60 cognitively unimpaired (CU) individuals. Within-network connectivity was calculated within the frontal eye field (FEF) and intraparietal sulcus (IPS) and the entire DAN. Between-network connectivity was calculated with default mode network (DMN), frontoparietal, and visual networks. Models were fit to compare network connectivity between both groups and assess relationships between connectivity, gray matter volumes, and clinical test scores in PCA. PCA showed reduced within-network connectivity in DAN, specifically within the IPS, compared to CU individuals. The DAN, particularly the FEF, showed an increase in between-network connectivity with the frontoparietal network but no relationship to the DMN and visual networks. Lower DAN connectivity was associated with a trend for smaller volumes in the entire network and significantly lower scores on the auditory verbal learning test-recognition percent correct and Wechsler Memory Scale III-digit span backward in PCA patients. Our results showed disruptions in DAN connectivity, particularly in the posterior regions, which could be contributing to episodic and working memory deficits in PCA. Heightened connectivity between the DAN and the frontoparietal network suggests a compensatory mechanism to preserve attention function.