[FieldTrip] MEG Time-Frequency testing (ft_freqstatistics)

[Tavabi, Kambiz]

Eric,
>"Fieldtrippers" may have connotations that a scientist does not always
>appreciate, but what to think of "Fieldstrippers"?
Touche. 
>Have a look at the (channel,frequency)-specific paired t-tests.
I am not sure exactly what you mean. By 'specific' do you mean sample wise testing in a narrow frequency range?

-K.
-------------------------------------------------------------
Kambiz Tavabi PhD
Biomedical Imaging Laboratory
The Children's Hospital of Philadelphia
34th Street and Civic Center Boulevard
Philadelphia, Pa. 19104
Tel: 267.426.0302
email: tavabik at email.chop.edu
-------------------------------------------------------------
________________________________________
From: fieldtrip-bounces at donders.ru.nl [fieldtrip-bounces at donders.ru.nl] On Behalf Of Eric Maris [e.maris at donders.ru.nl]
Sent: Wednesday, December 15, 2010 5:36 PM
To: 'Email discussion list for the FieldTrip project'
Subject: Re: [FieldTrip] MEG Time-Frequency testing (ft_freqstatistics)

Dear Kambiz,


> Greetings Fieldstrippers

"Fieldtrippers" may have connotations that a scientist does not always
appreciate, but what to think of "Fieldstrippers"?

> My problem with the results in the attachment is that in the grand
> averages there is an obvious event related desynchrony (cold colors,
> negative values) difference between 0.4-0.8sec; 10-40hz which somehow
> doesn't get picked up, but the small blip of noise/event-related
> synchrony (hot colors, positive values) c. 0.5sec at 50Hz is revealed
> as different between conditions by the permutations!

Have a look at the (channel,frequency)-specific paired t-tests. Do these
detect the big cold blob? If not, the variance across subjects is probably
large.


Best,

Eric Maris






To carry out the
> permutations I used
> cfg.method           = 'montecarlo';
> cfg.statistic        = 'depsamplesT';
> cfg.correctm         = 'cluster';
> cfg.clusteralpha     = 0.05;
> cfg.clusterstatistic = 'maxsum';
> cfg.neighbours       = [ ];
> cfg.tail             = 0;
> cfg.clustertail      = 0;
> cfg.alpha            = 0.05;
> cfg.numrandomization = 500;
> So I presume that the result is not due to a signs (pos/neg values)
> issue, if I am using a two-tailed test. Changing cfg.tail &
> cfg.clustertail to 1 makes little to no difference, and a value of -1
> results in errors. Basically, I'd appreciate if someone, based on what
> is observable in the grand averages, could confirm that the permutation
> result makes sense? And if not then some advice on what I am doing
> wrong. Thank you. -Kambiz
>
> -K.
> ------------------------------------------------------------
> Kambiz Tavabi PhD
> Biomedical Imaging Laboratory
> The Children's Hospital of Philadelphia
> 34th Street and Civic Center Boulevard
> Philadelphia, Pa. 19104
> Tel: 267.426.0302
> email: tavabik at email.chop.edu<mailto:tavabik at email.chop.edu>
> ------------------------------------------------------------


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