Significance test frequency power decrease baseline vs stimulation

[Nathan Weisz]

hi,

you want individual subject stats? i'm pretty sure then that you need  
to add something like
cfg.keeptrials='yes';
when doing your freqanalysis.

btw, adding the actual error message is also a good idea when posting  
questions.

good luck,
n


On 26.06.2008, at 00:09, Thomas Dijkman wrote:

> Hi,
>
> For my bachelor's assignment, I'm trying to find a visual stimulus  
> of a hand
> movement that triggers the 'largest' modulation of the EEG. I.e. ,  
> when the
> subject looks at a right hand movement, literature suggest a  
> decrease in
> power in the 8-13 Hz band, relative to a baseline period around  
> electrode
> position C3.
> I'm trying to use Fieldtrip's freqstatistics.m function to test this
> decrease in power for significance. Following a tutorial in the  
> Fieldtrip wiki,
> http://www2.ru.nl/fcdonders/fieldtrip/doku.php?id=fieldtrip:documentation:tutorial:statistics&s=freqstatistics#3.2_permutation_tests_for_time-frequency_representationswithin_trial_experiments
>
> which I thought applied to my situation gave me a lot of error  
> messages.
>
> I've already redefined my trials, so I have a separate set of  
> trials, one
> containing 2 seconds of baseline, and one containing 2 seconds of  
> stimulus.
> The baseline time axis is shifted so it overlaps the stimulus time  
> axis
>
> I then use this code to calculate TFR's for those datasets:
>
> cfgfreq.method = 'mtmconvol';
> cfgfreq.output = 'pow' ;
> cfgfreq.taper = ' hanning' ;
> cfgfreq.foi = 8:1:13;
> cfgfreq.t_ftimwin = 10./cfgfreq.foi;
> cfgfreq.toi = 5:1/100:7;
> cfgfreq.tapsmofrq = cfgfreq.foi*0.4;
> [baselineTFR] = freqanalysis(cfgfreq,baselinedata);
> [stimulusTFR] = freqanalysis(cfgfreq,stimulusdata);
>
> And then I have to do the significance test.
>
> cfg = [];
> sfg.method = 'analytic';
> cfg.statistics = 'actvsblT';
> cfg.alpha = 0.05;
> ?
> [stat] = freqstatistics(cfg,stimulusTFR,baselineTFR);
>
> I think I have to do something with the design matrix, but I can't  
> find
> anything about that in the wiki (or the rest of the internet).
>
> Thanks,
>
> Thomas
>
> ----------------------------------
> The aim of this list is to facilitate the discussion between users  
> of the FieldTrip  toolbox, to share experiences and to discuss new  
> ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html 
>  and http://www.ru.nl/fcdonders/fieldtrip.

--------------------------------
Dr. Nathan Weisz

INSERM - Unité 821
Dynamique cérébrale et cognition
Centre Hospitalier Le Vinatier, Bâtiment 452
95 Boulevard Pinel
69500 Bron, France

Tel: ++33 - (0)4 - 7213 8915
Email: nathan.weisz at inserm.fr
Chat-AV: nathanweisz at mac.com
Homepage: http://web.mac.com/nathanweisz
Neurotree: http://neurotree.org/neurotree/tree.php?pid=8692

Please avoid sending me Word or PowerPoint attachments.
See http://www.gnu.org/philosophy/no-word-attachments.html





----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.
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