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Dear all
I need some advice and help with DCM.
The study involved a replication of Jung’s original Word Association test under fMRI conditions. The subject is asked to respond with the first word that comes to mind in response to a stimulus word from a standard list. Most responses are bland and neutral, but some of them are not. Response time is prolonged, response are often idiosyncratic and affect –laden. Jung inferred internal conflict (his so-called “complexes”) from these unusual responses.
We ran 14 subjects thru 100 words, 20 second epoch for each . We compared complexed versus neutral responses for the group for the entire 20 sec epoch. (using SPM 5)
I also split it up into 3 second bits (first 3 seconds, 2nd 3 etc etc) to get some idea of what goes on over time, to construct a functional hypothesis that could be subjected to DCM testing. .
The complexed responses “pattern” that survived FWE correction seem to go like this.
FIRST 3 SECS.
There is strong activation (corrected for FEW) in (1) L Broca’s pre Broca’s, Z 5.58 (2) the L Middle temporal lobe Z 4.96, (3) L SMA/middle cingulate Z 4.97 and (4) L Anterior Insula Z 5.11 (all probably reflecting the conflicted word searching of a complexed response).
But there is also homologous activation of all these areas in the R hemisphere, albeit more weakly. (???interhemispheric negotiation/chatter whatever). (R Broca Z 4.85, R Mid Temp Z 4.77, R insula Z 4.77)
However, there is a SMALL area in R prefrontal region at 54,4, 47 (R precentral Area 6), which stands out on its own, 16 voxel Z 5.38, p FWE corr .001. This is the second strongest response in the entire result list. I don’t know what to make of it.
SECOND THREE SECS.
Same as above , BUT, there is a brief bit of R supraorbital (43 29 -6) activity (p FWE corr .038, Z 4.14) probably to do with the executive effort of the conflictual nature of the “complexed’ response. And activity shifts to from L to R SMA Z 5.28 !
The REST of the epoch achieves nothing that passes the FWE FDR barrier.
So I suppose a model might say that there is some some antero-posterior (receptive-expressive verbal) activity; with inter-hemispheric negotiations which include SMA and cingulum; and cortico-mesencephalic-limbic (Bilateral Anterior Insula) interaction, with R supraorbital (executive function) region coming on line a little later.
But this still doesn’t account for the weird SMALL but very prominent R precentral Area 6 region at 54,4, 47 .
Does anyone have any suggestions on how I might model this in DCM? Or for that matter whether DCM could even do this in principle? Since my limited understanding of DCM is that you can only do about 3 ROIs at a time ?
I’ve asked my local colleagues, but they can’t seem to come up with anything.
.
Leon