At 19:37 09/07/2007, Brianna Schuyler wrote:
>Hello,
>
>I'm interested in using DCM to look at the strength and
>directionality of connections between regions in my fMRI analysis,
>but I was wondering if there is any way to look at differences
>between groups, for example between controls and a patient
>population. From what I understand, the DCM analysis is done on
>each subject individually, so is it possible to find sigificant
>differences in certain parameters and infer differences in
>connectivity from that?
>
>Thanks very much for any help,
>Brianna Schuyler
>UW-Madison Dept of Psychology
Dear Brianna,
Yes, it is perfectly feasible to perform second-level statistical
tests on corresponding parameter estimates from (structurally
identical) DCMs of multiple subjects. This has been used in quite a
few studies before. For an example that includes only a single group
but also demonstrates how to do model comparison across subjects, see
Stephan KE, Marshall JC, Penny WD, Friston KJ, Fink GR.
Interhemispheric integration of visual processing during task-driven
lateralization.
J Neurosci. 2007 Mar 28;27(13):3512-22.
For a DCM example that compares patients with healthy controls see
Sonty SP, Mesulam MM, Weintraub S, Johnson NA, Parrish TB, Gitelman DR.
Altered effective connectivity within the language network in primary
progressive aphasia.
J Neurosci. 2007 Feb 7;27(6):1334-45.
Best wishes,
Klaas
_____________________________________
Klaas Enno Stephan, MD PhD
Senior Research Fellow, IoN
Wellcome Trust Centre for Neuroimaging
Institute of Neurology (IoN)
12 Queen Square, WC1N 3BG, London, UK
phone: +44-207-8337481
fax: +44-207-8131420
web: http://www.fil.ion.ucl.ac.uk/~kstephan/
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