[FieldTrip] Post-hoc tests for cluster-based permutation tests on event-related fields

Jack Gao chuanjigao at gmail.com
Mon Mar 27 14:30:44 CEST 2017

Dear Community,

My name is Chuanji Gao, I'm a PhD student in Experimental Psychology Program
at University of South Carolina. I'm now analyzing EEG data to get some
fields results.

There are three conditions (condition1, 2 and 3) that I want to compare. So
I used
ft_timelockstatistics to run the cluster-based permutation test firstly.
The cfg are as below.


*cfg = [];...cfg.neighbours  = neighbours;...*

*cfg.latency     = [0.1 0.8];cfg.avgovertime = 'no';cfg.parameter   =
'avg';cfg.method      = 'montecarlo';cfg.statistic   =
'depsamplesFmultivariate'; *

*...Nsub = 19;cfg.design(1,1:3*Nsub)  = [ones(1,Nsub) 2*ones(1,Nsub)
3*ones(1,Nsub)]; cfg.design(2,1:3*Nsub)  = [1:Nsub 1:Nsub
1:Nsub];cfg.ivar                = 1; cfg.uvar                = 2; stat =
ft_timelockstatistics(cfg,cond1{:},cond2{:}, cond3{:});*
The null hypothesis was rejected, and it seems the effect was most
from 224ms to 800ms at centro-parietal regions.

The next step: I want to do pairwise comparisons of the three conditions.
I'm not sure if I should use the time window identified from the last
analyses as below:

*...cfg.latency     = [0.224 0.8];cfg.avgovertime = 'yes';cfg.parameter   =
'avg';cfg.method      = 'montecarlo';cfg.statistic   =
'ft_statfun_depsamplesT'; *

*...stat = ft_timelockstatistics(cfg,cond1{:},cond2{:});*

OR should I use the whole time window as I used in the first analyses as

*...cfg.latency     = [0.1 0.8];cfg.avgovertime = 'no';cfg.parameter   =
'avg';cfg.method      = 'montecarlo';cfg.statistic   =
'ft_statfun_depsamplesT'; ...stat =

I'm inclined to use the whole time window and "non-average over time", but
entirely sure. Can someone give me some suggestions on it? Any help would be
very appreciated.

Chuanji Gao
PhD student
Department of Psychology
University of South Carolina

E-Mail chuanji at email.sc.edu
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