Dear FSL Experts,
We would like to do as follows:
(1) standard FEAT analysis in 3D native (EPI) space
(2) anatomical normalization in spherical standard space using Freesurfer
(3) anatomically normalized surfaces are projected (using equal area Mollweide projection) to a 2D space separately for each hemi
(4) the results of 3D FEAT analysis are transformed to 2D space for across the subjects analysis
Finally, we would like to run FLAME (analysis across subjects) with cluster correction on the flattened 2D data.
(In the flattened 2D space, EPI data files are similar to single slice data)
We would like to verify whether the FSL cluster correction works ok in the 2D data. Our (practical) tests suggest that it does: the results of a full 3D analysis (feat, group analysis and cluster correction in 3D) flattened to 2D and the results of 2D group analysis (feat in 3D, group analysis and cluster correction in 2D) produce nearly identical results (some tiny clusters do not survive in the 2D analysis).
Are there any noteworthy issues or potential pitfalls with this approach (cluster correction in 2D)?
(We could live with the facts that some activations are lost in the 3D->2D projection, that some tiny but real clusters will not survive cluster correction in 2D, and that p-values associated with 2D clusters could be different than those of the corresponding 3D clusters)
We would like to do the group analysis in the 2D space because, according to our understanding, it is not currently possible to use FSL cluster correction in the spherical space. We would like to use FSL tools throughout the statistical analysis (and not to use FLAME and, say, FS cluster correction in the spherical space).
Cheers,
Teemu Rinne
Institute of Behavioural Sciences
University of Helsinki
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