Population shrinkage of covariance (PoSCE) for better individual brain functional-connectivity estimation.

•Population shrinkage of covariance estimator (POSCE) integrates prior knowledge of covariance distribution over a large population.•POSCE relies on Riemannian geometry coupled with a probabilistic modeling of the individual and population covariance distributions.•POSCE yields more accurate age prediction from rest-fMRI (CamCAN,n=626) compared to classical functional connectivity estimators.•POSCE better relates functional connectivity measures to cognition and shows higher test/retest performance (HCP, n=815).•POSCE exhibits more sensitivity to similarity between twins wrt siblings or unrelated individuals (HCP, n=815).