[Mne_analysis] permutation cluster t-test for planar grads

Lucy MacGregor Lucy.MacGregor at mrc-cbu.cam.ac.uk
Tue Apr 12 09:28:13 EDT 2016
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Dear MNE users,

I wish to run permutation cluster t-test (2-tailed) on my sensor level data (cond A vs. cond B). I am wondering how best to deal with the planar gradiometer data from a Neuromag 306 system and would be grateful for advice.

Since I am not interested in the direction of the gradients at individual gradiometers within a pair, I think it makes most sense to combine the data for each 102 pairs using RMS (for each gradiometer then RMS(g) = sqrt(sum(g₁²+g₂²)/2)). I would perform the t-tests on these RMS data. I then wondered how neighbourhood definitions for clustering ought to be defined - I was thinking I could replace my magnetometer values with the new RMS gradiometer values and use the neighbourhood definitions from “neuromag306mag”.

I took the options for the neighbourhood templates after reading this page here:

Does this make sense or would you suggest a different approach? Ought I to obtain t-values for each of the 204 gradiometers and perform the clustering on these values instead?

Many thanks for any guidance,

Lucy MacGregor

Lucy MacGregor
MRC Cognition and Brain Sciences Unit
15 Chaucer Road
Cambridge CB2 7EF
Tel: 01223 355294 Ext 860

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