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Hi David,
A couple of options. One is to set p=1 at the single subject level. Then you’ll get all activity in the region. The other alternative is to look for the nearest
peak (e.g. p < 0.001) in each subject within some radius of the group peak.
Best,
Peter.
From: David Hofmann [mailto:[log in to unmask]]
Sent: 29 July 2014 15:40
To: Zeidman, Peter
Cc: [log in to unmask]
Subject: Re: [SPM] DCM: Group comparison & defining ROIs
Thanks Peter,
what would be a liberal threshold in this case? Since there may be no activation in the ROI I chose at group level in a subject I can't extract the timecourse via the Eigenvariate-button. Does this mean I have to choose a significance level where
there is activation everywhere?
Or is there another way to extract timecourse data by means of coordinates?
greetings
David
2014-07-29 15:41 GMT+02:00 Zeidman, Peter <[log in to unmask]>:
Hi David,
That’s fine – not every subject needs individual level activation (although this could indicate different
subjects are using different cognitive processes?).
A note of caution in case you’re using the GUI to extract ROIs… When you click the ‘eigenvariate’
button, the crosshairs will jump to the nearest activation. To prevent this you’d have to set the significance threshold to a very liberal value.
Best,
Peter.
From: SPM
(Statistical Parametric Mapping) [mailto:[log in to unmask]]
On Behalf Of David Hofmann
Sent: 29 July 2014 13:41
To: [log in to unmask]
Subject: [SPM] DCM: Group comparison & defining ROIs
Hi @all,
when defining ROIs for a DCM group analysis, is it necessary that in
every subject those ROIs need to be significantly activated (e.g. with F-test over all effects of interest at p = 0.001 uncorrected)?
With 2nd level analysis I can define some ROIs with significant activation, but those are not active in every single person.
greetings
David
--
David Hofmann (M.Sc.)
Institut für Medizinische Psychologie und Systemneurowissenschaften
Von-Esmarch-Strasse 52
48149 Münster
Tel: 0251/ 8352794
Mobil: 0152/ 09822352
Email: [log in to unmask]
Institute of Medical Psychology and Systems Neuroscience
University of Muenster
Von-Esmarch-Str. 52
D-48149 Muenster, Germany
Phone: +49 (0) 251 - 83 52794
Mobile: +49 (0) 152 - 09822352
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