[FieldTrip] Cluster Based Permutation Stats on Source Spaced Frequency Data

[Martin Holding]

Hello Fieldtrip,

This is my first posting so I'll introduce myself. My name is Martin and I'm a PhD student at the Institute of Hearing Research in Nottingham, primarily interested in auditory oscillations associated with tinnitus using EEG and MEG.  This problem is from a project I did a while back but I'm just wrapping up now.

I'm having a problem with running some cluster based permutation statistics on some frequency and timelocked MEG data I have. The first thing to mention is that the code runs fine. Fieldtrip is happy to run the tests, the problem is that I am getting no significant clusters out of it. This is in spite of some rather large t-values that might suggest otherwise. I suspect this is due to the fact that the frequency and timelocked data I am passing to the relevant stats functions (ft_freqstatistics and ft_timelockstatistics respectively) is analysed in source space, not sensor space. Unfortunately, due to data artefacts it isn't possible for me to do these analyses in sensor space. As such, I think that fieldtrip is telling me I have no clusters because it defines clusters based on neighbouring channels/sensors supplied by a layout template which it no longer has access too because I'm in source space on an MNI grid system.

I have 2 questions then:


1.       Is this a sensible conclusion for why I'm getting no significant clusters?

2.       And if so, is there a way I can make the fieldtrip statistics functions recognise MNI grids and calculate the neighbours on grid points rather than sensors?

Many thanks,

Martin

==============================================================
Martin Holding
PhD Student
MRC Institute of Hearing Research
University Park
Nottingham
NG7 2RD

Tel: (0115 74) 86938
Email: martin.holding at nottingham.ac.uk<mailto:martin.holding at nottingham.ac.uk>



==============================================================
Martin Holding
PhD Student
MRC Institute of Hearing Research
University Park
Nottingham
NG7 2RD

Tel: (0115 74) 86938
Email: martin.holding at nottingham.ac.uk





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