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| Research article summary (published 29 Sep 2002): |
Simulation of the effects of global normalization procedures in functional MRI.
Full Abstract
We report on differences in sensitivity and false-positive rate across five methods of global normalization using resting-state fMRI data embedded with simulated activation. These methods were grand mean session scaling, proportional scaling, ANCOVA, a masking method, and an orthogonalization method. We found that global normalization by proportional scaling and ANCOVA decreased the sensitivity of the statistical analysis and induced artifactual deactivation even when the correlation between the global signal and the experimental paradigm was relatively low. The masking method and the orthogonalization method performed better from this perspective but are both restricted to certain experimental conditions. Based on the results of these simulations, we offer practical guidelines for the choice of global normalization method least likely to bias the experimental results.
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Author information
Author/s: Gavrilescu, Maria (M); Shaw, Marnie E (ME); Stuart, Geoffrey W (GW); Eckersley, Peter (P); Svalbe, Imants D (ID); Egan, Gary F (GF);
Affiliation: Howard Florey Institute, University of Melbourne, Australia.
Journal and publication information
Publication Type: Clinical Trial; Journal Article
Journal: NeuroImage (Neuroimage), published in United States. (Language: eng)
Reference: 2002-Oct; vol 17 (issue 2) : pp 532-42
Dates: Created 2002/10/14; Completed 2002/11/25; Revised 2004/11/17;
PMID: 12377132, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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