[Mne_analysis] permutation cluster t-test for planar grads

[Lucy MacGregor]

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:
http://martinos.org/mne/dev/generated/mne.channels.read_ch_connectivity.html#mne.channels.read_ch_connectivity


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
http://www.mrc-cbu.cam.ac.uk/people/lucy.macgregor/


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