Xingbao Li wrote:
> Dear Dr. Penny
>
> I have several questions for you in DCM perform. My study is using interleaved TMS/fMRI technique
> to explore different networks related to prefrontal cortex stimulation or motor cortex
> stimulation. We have 10 healthy subjects to be scanned in MRI scanner with TMS stimulation over
> motor cortex and prefrontal cortex. SPM reults show different activated region between motor
> stimulation and prefrontal stimulation. Now I want to identify different networks activated by
> motor TMS and prefrontal TMS. I have tried individual data for DCM and got some questions.
>
> 1. I performed DCM at an individual level and could not got DCM-output matrix. (see attached tiff
> file).
>
This information is also contained within the DCM data structure.
Load the DCM*.mat file into matlab and have a look at DCM.A, DCM.B, DCM.C.
The probability that individual connections are larger than DCM.T is given by the
probabilities in the matrices DCM.pA, DCM.pB and DCM.pC
> 2. How can I get a group DCM results? May I use the group t-map or F-map to create VOIs, then use
> these VOIs to perform DCM for each subject? Within DCM, can I average and compare DCM to get
> group data? Is this correct?
>
No. The best approach here is to do a DCM analysis for each subject and then
do a one-sample t-test on the connection of interest eg. say you're interested in
the strength of the modulatary connection from region 1 to region 2. Extract DCM.B(2,1) (I think
this is the right way round - but check !) for each subject then do the one sample t-test to
see if the effect is significantly non-zero in the population.
> 3. When to perform DCM, are there some limitation for the number of VOIs? When I perform DCM
> within 8 VOIs, the window can not show up 'Done' box.
>
Yes - this is the limit in the visual display. Its also close to the limit computationally
(depending on how long the time series are).
> 4. Where can I get a instruction or manual for DCM?
>
There is;nt a manual. SOrry.
All we have is the analysis of an example data set
http://www.fil.ion.ucl.ac.uk/~wpenny/datasets/attention.html
and a description of the DCM updates
http://www.fil.ion.ucl.ac.uk/~wpenny/publications/DCM_updates.doc
Best,
Will.
> Thanks,
>
> Xingbao Li
>
>
>
> Xingbao Li M.D. Research Scientist Brain Stimulation Laboratory Center for Advanced Imaging
> Research Departments of Psychiatry and Radiology Medical University of South Carolina 67
> President St, Rm 502 N PO Box 250861 Charleston, SC 29425 tel:843-7925-729 fox:843-7925-702
> Email:[log in to unmask] websites:http://www.musc.edu/psychiatr/fnrd/function.htm
> http://www.musc.edu/psychiatry/fnrd/tms.htm
>
--
William D. Penny
Wellcome Department of Imaging Neuroscience
University College London
12 Queen Square
London WC1N 3BG
Tel: 020 7833 7475
FAX: 020 7813 1420
Email: [log in to unmask]
URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
|