Age-related compression of posterior cingulate-retrosplenial connectivity gradients and its association with allocentric navigation.

Allocentric spatial navigation declines with age, but the underlying neural mechanisms remain unclear. The posterior cingulate/retrosplenial cortex (PCC/RSC) is an integrative navigation hub and is also among the earliest regions affected by aging. We investigated whether the PCC/RSC is organized along continuous functional connectivity gradients, and how these gradients relate to age and spatial navigation ability. Using an adult-lifespan sample from the Southwest University Adult Lifespan Dataset (SALD; n = 479; age range = 19-80 years), we characterized functional connectivity gradients within the PCC/RSC complex and examined their associations with age. Two dominant functional connectivity gradients (G1 and G2) were identified within the PCC/RSC complex. The ranges of both gradients decreased significantly with age. In an independent navigation sample comprising 19 younger and 19 older adults, participants underwent resting-state fMRI and task-based fMRI while performing an allocentric object-location memory task. We examined whether age-related gradient compression was also evident in this independent navigation sample and whether gradient range was associated with navigation performance. Older adults showed smaller task-state left G1, task-state right G2, and resting-state right G2 ranges, with the largest reduction in task-state left G1 (approximately 65%). Among older adults, greater task-state left G1 range was associated with lower drop error. These findings provide novel evidence that age-related compression of PCC/RSC functional organization is behaviorally relevant to allocentric navigation decline.