The Effect of Choice of Metric and Scan Length on Reliability in Resting-State fMRI

2026-05-30

AI Summary

This study addresses the reproducibility of resting-state fMRI functional connectivity by systematically evaluating the impact of different distance metrics and scan duration on reliability. Leveraging the multi-session, long-duration data from the Midnight Scanning Club, the authors employ a distance-based intraclass correlation coefficient (dbICC) framework to compare, for the first time, the Affine Invariant Riemannian Metric against the conventional Frobenius norm, with functional connectivity matrices constructed using Pearson correlation. The findings reveal that longer scan durations substantially enhance reliability, whereas the interval between sessions exerts minimal influence. Although the two metrics yield consistent results in certain aspects, they diverge significantly in critical reliability assessments, underscoring the profound impact of metric choice on the interpretation of functional connectivity outcomes.

Abstract

Resting-state fMRI (rs-fMRI) is widely used to investigate brain functional connectivity, but the reliability of these measurements remains a key concern for ensuring reproducibility. The distance-based intraclass correlation coefficient (dbICC) generalizes classical ICC to more general data types, making it well-suited for assessing the reliability of measures of functional connectivity. In this study, we applied dbICC to assess the reliability of rs-fMRI data from the Midnight Scanning Club (MSC) dataset, which consists of 10 subjects, each undergoing 10 sessions of 30-minute rs-fMRI scans. The functional connectivity was estimated using Pearson's correlation coefficients between all pairs of brain regions, resulting in a correlation matrix for each session. We compared two distance metrics-the widely used Frobenius metric and the Affine Invariant Riemannian Metric (AIRM) selected to respect the geometry of the space of covariance matrices-to evaluate how the choice of metric affects the reliability of estimating correlation. In addition, we investigated the impact of scan length and time interval between sessions on reliability. Results based on each metric agreed in some respects but disagreed in others, illustrating the impact of choice of metric. We also found that longer scan lengths significantly improve reliability, while the time interval between sessions has less impact.

Problem

• reliability
• resting-state fMRI
• functional connectivity
• scan length
• distance metric

Innovation

• dbICC
• functional connectivity
• Affine Invariant Riemannian Metric
• reliability
• resting-state fMRI