[FieldTrip] Group level source statistics for individual condition

Passaro, Antony D Antony.Passaro at uth.tmc.edu
Mon Jul 18 14:55:08 CEST 2011

Dear Don,

Thank you for replying to my issue regarding group statistics. I apologize for not elaborating on what I did at the subject level...for each subject I compared the source estimation (dics beamformer) of the pre-stimulus to the post-stimulus using sourcestatistics for each of the two conditions. I then compared the two conditions directly across all subjects for a group level comparison using sourcestatistics again. I would like to also look at the statistically significant activation associated with each condition compared to baseline across the entire group. The solution that I came up with involves appending all trials for all subjects together into one large pseudo-subject and performing the sourcestatistics. I have tried to normalize the source results using volumenormalise in the past but I always received an error from sourcestatistics after performing that step, I think it has to be in the native source space to perform the statistics? I can run it again to find out the exact error that it gives.

Thank you,

From: fieldtrip-bounces at donders.ru.nl [mailto:fieldtrip-bounces at donders.ru.nl] On Behalf Of Rojas, Don
Sent: Friday, July 15, 2011 2:05 PM
To: Email discussion list for the FieldTrip project
Subject: Re: [FieldTrip] Group level source statistics for individual condition

Dear Tony,

You don't really give details of what you did on the single subject level that you want to try to achieve on the group level. But appending all the subject sources to each other does not make sense to me. Assuming you wrote out all the sources you computed as image files, then within Fieldtrip you can use ft_volumenormalise to write the results to standard source space (which uses SPM2 or SPM8). Or, you can just use SPM8 directly, taking the normalization result from the T1 MRI data and applying it to the source result computed within that space. That will put your subjects in MNI space and then you can do stats from there in a common anatomical space.


Don Rojas, Ph.D.
Associate Professor of Psychiatry
U. of Colorado Denver Anschutz Medical Campus
Director, UCD Magnetoencephalography Lab
13001 E. 17th Pl F546
Aurora, CO 80045
On Jul 15, 2011, at 11:04 AM, Passaro, Antony D wrote:

Hi everyone,

I tried to come up with a solution to this issue and the best I could do was to append all source analyses of pre-stim and post-stim trials for each subject to one another before performing source statistics across all trials and all subjects. However, I cant seem to find a way to normalize all subjects so they reside in the same source space prior to performing source statistics.

Any help would be much appreciated.


From: fieldtrip-bounces at donders.ru.nl<mailto:fieldtrip-bounces at donders.ru.nl> [mailto:fieldtrip-bounces at donders.ru.nl] On Behalf Of Passaro, Antony D
Sent: Monday, July 11, 2011 8:25 AM
To: fieldtrip at donders.ru.nl<mailto:fieldtrip at donders.ru.nl>
Subject: [FieldTrip] Group level source statistics for individual condition

Hi all,

I'm trying to figure out how to compute the source statistics across a group of subjects for an individual condition (as compared to baseline). I have performed the single subject level source statistics for each condition compared to baseline (for all trials) and I have used those results to compute the group level statistics comparing both conditions directly. But I would also like to show the statistically significant sources across the group for each condition and while the average across subjects is informative, I would prefer to perform the same type of statistical analysis that was used to compare conditions directly. Is this possible with Fieldtrip and if so, would it require averaging the baseline and condition separately across all trials for each subject before comparing the condition and baseline at the group level using the sourcestatistics function?

Thank you for your help,
fieldtrip mailing list
fieldtrip at donders.ru.nl<mailto:fieldtrip at donders.ru.nl>

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