title: The effect of scan length on the reliability of resting-state fMRI connectivity estimates.
abstract: There has been an increasing use of functional magnetic resonance imaging (fMRI) by the neuroscience community to examine differences in functional connectivity between normal control groups and populations of interest. Understanding the reliability of these functional connections is essential to the study of neurological development and degenerate neuropathological conditions. To date, most research assessing the reliability with which resting-state functional connectivity characterizes the brain's functional networks has been on scans between 3 and 11 min in length. In our present study, we examine the test-retest reliability and similarity of resting-state functional connectivity for scans ranging in length from 3 to 27 min as well as for time series acquired during the same length of time but excluding half the time points via sampling every second image. Our results show that reliability and similarity can be greatly improved by increasing the scan lengths from 5 min up to 13 min, and that both the increase in the number of volumes as well as the increase in the length of time over which these volumes was acquired drove this increase in reliability. This improvement in reliability due to scan length is much greater for scans acquired during the same session. Gains in intersession reliability began to diminish after 9-12 min, while improvements in intrasession reliability plateaued around 12-16 min. Consequently, new techniques that improve reliability across sessions will be important for the interpretation of longitudinal fMRI studies.
authors.affiliation: Department of Psychiatry, University of Wisconsin-Madison, Madison, WI, USA; Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, USA; Neurosciences Training Program, University of Wisconsin-Madison, Madison, WI, USA. Electronic address: rbirn@wisc.edu.
authors.forename: Rasmus M
authors.initials: RM
authors.lastname: Birn
authors.forename: Erin K
authors.initials: EK
authors.lastname: Molloy
authors.forename: Rémi
authors.initials: R
authors.lastname: Patriat
authors.forename: Taurean
authors.initials: T
authors.lastname: Parker
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Meier
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Kirk
authors.forename: Veena A
authors.initials: VA
authors.lastname: Nair
authors.forename: M Elizabeth
authors.initials: ME
authors.lastname: Meyerand
authors.forename: Vivek
authors.initials: V
authors.lastname: Prabhakaran
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D063132:Connectome / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D015203:Reproducibility of Results; D012146:Rest / Q000502:physiology*; D018401:Sample Size; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: Functional connectivity; Reliability; Resting-state; Scan duration; Scan length; fMRI