Reliability Correction for Functional Connectivity

Network properties can be estimated using functional connectivity MRI (fcMRI). However, regional variation of the fMRI signal causes systematic biases in network estimates including correlation attenuation in regions of low measurement reliability. Here we computed the spatial distribution of fcMRI reliability using longitudinal fcMRI datasets and demonstrated how pre-estimated reliability maps can correct for correlation attenuation. As a test case of reliability-based attenuation correction we estimated properties of the default network, where reliability was significantly lower than average in the medial temporal lobe and higher in the posterior medial cortex, heterogeneity that impacts estimation of the network. Accounting for this bias using attenuation correction revealed that the medial temporal lobe’s contribution to the default network is typically underestimated. To render this approach useful to a greater number of datasets, we demonstrate that test-retest reliability maps derived from repeated runs within a single scanning session can be used as a surrogate for multisession reliability mapping. Using data segments with different scan lengths between 1 and 30 min, we found that test-retest reliability of connectivity estimates increases with scan length while the spatial distribution of reliability is relatively stable even at short scan lengths. Finally, analyses of tertiary data revealed that reliability distribution is influenced by age, neuropsychiatric status and scanner Additional Supporting Information may be found in the online version of this article. Contract grant sponsor: German Research Foundation (to S.M.); Contract grant number: MU 3222/2-1; Contract grant sponsor: NIH (to H.L.); Contract grant numbers: 1K25NS069805, R01NS091604, and P50MH106435; Contract grant sponsor: NARSAD Young Investigator Grant; Contract grant sponsor: NIH (to M.D.F.); Contract grant number: K23NS083741; Contract grant sponsor: AAN/American Brain Foundation. *Correspondence to: Hesheng Liu, Suite 2301, 149 13th St. Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, 02129. E-mail: Hesheng@ nmr.mgh.harvard.edu or Wei Sun, Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing 100053, China. E-mail: [email protected] Received for publication 8 April 2015; Revised 18 July 2015; Accepted 6 August 2015. DOI: 10.1002/hbm.22947 Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com). r Human Brain Mapping 00:00–00 (2015) r VC 2015 Wiley Periodicals, Inc. type, suggesting that reliability correction may be especially important when studying between-group differences. Collectively, these results illustrate that reliability-based attenuation correction is an easily implemented strategy that mitigates certain features of fMRI signal nonuniformity. Hum Brain Mapp 00:000–000, 2015. VC 2015 Wiley Periodicals, Inc.