Pantazis, Dimitrios, Nichols, Thomas E., Baillet, Sylvain and Leahy, Richard M.. (2005) A comparison of random field theory and permutation methods for the statistical analysis of MEG data. NeuroImage, Vol.25 (No.2). pp. 383-394. ISSN 1053-8119

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Abstract

We describe the use of random field and permutation methods to detect activation in cortically constrained maps of current density computed from MEG data. The methods are applicable to any inverse imaging method that maps event-related MEG to a coregistered cortical surface. These approaches also extend directly to images computed from event-related EEG data. We determine statistical thresholds that control the familywise error rate (FWER) across space or across both space and time. Both random field and permutation methods use the distribution of the maximum statistic under the null hypothesis to find FWER thresholds. The former methods make assumptions on the distribution and smoothness of the data and use approximate analytical solutions, the latter resample the data and rely on empirical distributions. Both methods account for spatial and temporal correlation in the cortical maps. Unlike previous nonparametric work in neuroimaging, we address the problem of nonuniform specificity that can arise without a Gaussianity assumption. We compare and evaluate the methods on simulated data and experimental data from a somatosensory-evoked response study. We find that the random field methods are conservative with or without smoothing, though with a 5 vertex FWHM smoothness, they are close to exact. Our permutation methods demonstrated exact specificity in simulation studies. In real data, the permutation method was not as sensitive as the RF method, although this could be due to violations of the random field theory assumptions.

Item Type:	Journal Article
Subjects:	Q Science > QA Mathematics R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Divisions:	Faculty of Science > Statistics
Library of Congress Subject Headings (LCSH):	Magnetoencephalography -- Data processing, Magnetoencephalography -- Statistics, Random fields, Permutations
Journal or Publication Title:	NeuroImage
Publisher:	Elsevier
ISSN:	1053-8119
Date:	5 February 2005
Volume:	Vol.25
Number:	No.2
Page Range:	pp. 383-394
Identification Number:	10.1016/j.neuroimage.2004.09.040
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
URI:	http://wrap.warwick.ac.uk/id/eprint/38226

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