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The empirical replicability of task-based fMRI as a function of sample size

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IMAGEN Consortium, Han Bossier, Sanne P Roels, Ruth Seurinck, Tobias Banaschewski, Gareth J Barker, Arun L W Bokde, Erin Burke Quinlan, Sylvane Desrivières, Herta Flor, Antoine Grigis, Hugh Garavan, Penny Gowland, Andreas Heinz, Bernd Ittermann, Jean-Luc Martinot, Eric Artiges, Frauke Nees, Dimitri Papadopoulos Orfanos, Luise Poustka & 6 more Juliane H Fröhner Dipl-Psych, Michael N Smolka, Henrik Walter, Robert Whelan, Gunter Schumann, Beatrijs Moerkerke

Original languageEnglish
Article number116601
JournalNeuroImage
Volume212
Early online date6 Feb 2020
DOIs
Publication statusPublished - 15 May 2020

Bibliographical note

Copyright © 2020. Published by Elsevier Inc.

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Abstract

Replicating results (i.e. obtaining consistent results using a new independent dataset) is an essential part of good science. As replicability has consequences for theories derived from empirical studies, it is of utmost importance to better understand the underlying mechanisms influencing it. A popular tool for non-invasive neuroimaging studies is functional magnetic resonance imaging (fMRI). While the effect of underpowered studies is well documented, the empirical assessment of the interplay between sample size and replicability of results for task-based fMRI studies remains limited. In this work, we extend existing work on this assessment in two ways. Firstly, we use a large database of 1400 subjects performing four types of tasks from the IMAGEN project to subsample a series of independent samples of increasing size. Secondly, replicability is evaluated using a multi-dimensional framework consisting of 3 different measures: (un)conditional test-retest reliability, coherence and stability. We demonstrate not only a positive effect of sample size, but also a trade-off between spatial resolution and replicability. When replicability is assessed voxelwise or when observing small areas of activation, a larger sample size than typically used in fMRI is required to replicate results. On the other hand, when focussing on clusters of voxels, we observe a higher replicability. In addition, we observe variability in the size of clusters of activation between experimental paradigms or contrasts of parameter estimates within these.

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