The Resting Brain: Unconstrained yet Reliable

TLDR

Resting‑state fMRI is widely used to study functional connectivity, yet its unconstrained nature raises concerns; nevertheless, connectivity patterns are consistently observed across studies, though test–retest reliability has not yet been established. Here, we quantify the test–retest reliability of resting‑state fMRI using scans from 26 participants at three time points. We assessed intersession (>5 months apart), intrasession (<1 h apart), and multiscan (across all three scans) reliability and consistency for both region‑of‑interest and voxel‑wise analyses. We found modest to high reliability across connections, with stronger reliability for significant, positive, and default‑mode network connections; global connectivity patterns were highly robust over short and long terms, and hierarchical clustering solutions were reproducible across participants and sessions, supporting the reliability of resting‑state fMRI.

Abstract

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 determined. 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) correlation significance (significantly nonzero > nonsignificant), 2) correlation valence (positive > negative), and 3) network membership (default mode > task positive network). Short- and long-term measures of the consistency of global connectivity patterns were highly robust. Finally, hierarchical clustering solutions were highly reproducible, both across participants and sessions. Our findings provide a solid foundation for continued examination of resting state fcMRI in typical and atypical populations.