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Robust and Unbiased Variance of GLM Coefficients for Misspecified Autocorrelation and Hemodynamic Response Models in fMRI
Author
Source
International Journal of Biomedical Imaging
Issue
Vol. 2009, Issue 2009 (31 Dec. 2009), pp.1-11, 11 p.
Publisher
Hindawi Publishing Corporation
Publication Date
2009-09-06
Country of Publication
Egypt
No. of Pages
11
Main Subjects
Abstract EN
As a consequence of misspecification of the hemodynamic response and noise variance models, tests on general linear model coe cients are not valid.
Robust estimation of the variance of the general linear model (GLM) coecients in fMRI time series is therefore essential.
In this paper an alternative method to estimate the variance of the GLM coe cients accurately is suggested and compared to other methods.
The alternative, referred to as the sandwich, is based primarily on the fact that the time series are obtained from multiple exchangeable stimulus presentations.
The analytic results show that the sandwich is unbiased.
Using this result, it is possible to obtain an exact statistic which keeps the 5% false positive rate.
Extensive Monte Carlo simulations show that the sandwich is robust against misspeci cation of the autocorrelations and of the hemodynamic response model.
The sandwich is seen to be in many circumstances robust, computationally efficient, and flexible with respect to correlation structures across the brain.
In contrast, the smoothing approach can be robust to a certain extent but only with specific knowledge of the circumstances for the smoothing parameter.
American Psychological Association (APA)
Waldorp, Lourens. 2009. Robust and Unbiased Variance of GLM Coefficients for Misspecified Autocorrelation and Hemodynamic Response Models in fMRI. International Journal of Biomedical Imaging،Vol. 2009, no. 2009, pp.1-11.
https://search.emarefa.net/detail/BIM-493490
Modern Language Association (MLA)
Waldorp, Lourens. Robust and Unbiased Variance of GLM Coefficients for Misspecified Autocorrelation and Hemodynamic Response Models in fMRI. International Journal of Biomedical Imaging No. 2009 (2009), pp.1-11.
https://search.emarefa.net/detail/BIM-493490
American Medical Association (AMA)
Waldorp, Lourens. Robust and Unbiased Variance of GLM Coefficients for Misspecified Autocorrelation and Hemodynamic Response Models in fMRI. International Journal of Biomedical Imaging. 2009. Vol. 2009, no. 2009, pp.1-11.
https://search.emarefa.net/detail/BIM-493490
Data Type
Journal Articles
Language
English
Notes
Includes bibliographical references
Record ID
BIM-493490