Cerebral Cortex doi:10.1093/cercor/bhn256 The Resting Brain: Unconstrained yet Reliable

Recent years have witnessed an upsurge in the usage of resting-state functional magnetic resonance imaging (fMRI) to examine functional connectivity (fcMRI), both in normal and pathological populations. Despite this increasing popularity, concerns about the psychologically unconstrained nature of the ‘‘resting-state’ ’ remain. Across studies, the patterns of functional connectivity detected are remarkably consistent. However, the test--retest reliability for measures of resting state fcMRI measures has not been de-termined. Here, we quantify the test--retest reliability, using resting scans from 26 participants at 3 different time points. Specifically, we assessed intersession (>5 months apart), intrasession (<1 h apart), and multiscan (across all 3 scans) reliability and consistency for both region-of-interest and voxel-wise analyses. For both approaches, we observed modest to high reliability across connections, dependent upon 3 predictive factors: 1) correlatio