Format

Send to

Choose Destination
See comment in PubMed Commons below
PLoS One. 2015 Apr 28;10(4):e0126255. doi: 10.1371/journal.pone.0126255. eCollection 2015.

Orthogonalization of regressors in FMRI models.

Author information

1
Center for Investigating Healthy Minds at the Waisman Center, University of Wisconsin-Madison, Madison, WI, USA.
2
Helen Wills Neuroscience Institute, Brain Imaging Center, University of California, Berkeley, CA, USA.
3
Department of Psychology, Stanford University, Palo Alto, CA, USA.

Abstract

The occurrence of collinearity in fMRI-based GLMs (general linear models) may reduce power or produce unreliable parameter estimates. It is commonly believed that orthogonalizing collinear regressors in the model will solve this problem, and some software packages apply automatic orthogonalization. However, the effects of orthogonalization on the interpretation of the resulting parameter estimates is widely unappreciated or misunderstood. Here we discuss the nature and causes of collinearity in fMRI models, with a focus on the appropriate uses of orthogonalization. Special attention is given to how the two popular fMRI data analysis software packages, SPM and FSL, handle orthogonalization, and pitfalls that may be encountered in their usage. Strategies are discussed for reducing collinearity in fMRI designs and addressing their effects when they occur.

PMID:
25919488
PMCID:
PMC4412813
DOI:
10.1371/journal.pone.0126255
[Indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Public Library of Science Icon for PubMed Central
    Loading ...
    Support Center