Dear DCM users,
we have conducted a repetition priming experiment in which subjects had to
decide whether pictured objects and words fitted into a shoebox or not. we
have built two similar DCMs, one working with separate experimental
condtitions and one working with experimental factors as regressors
in the design matrix.
1. DCM:
Conditions:
1. objects-1stPresentation
2. objects-2ndPresentation
3. words-1stPresentation
4. words-2ndPresentation
Regions:
LOTC (Left occipito temporal cortex)
LTPO
LSMG
vLIFG (ventral Left Inferior frontal gyrus)
dLIFG
MSF
Direct Effects:
All 4 Conditions on LOTC
Intrinsic connections:
All enabled
Modulatory effects:
All 4 Conditions on all connections (except connections of regions on
themselves).
2. DCM
Factors:
1. VISUAL (objetcs-1stPresentation, objects-2ndPresentation,
words-1stPresentation,words-2ndPresentation)
2. ISWORD (words-1stPresentation,words-2ndPresentation)
3. REPETITION (objects-2ndPresentation, words-2ndPresentation)
Regions: same as 1. DCM
Direct Effects:
VISUAL on LOTC
Intrinsic connections:
All enabled
Modulatory effects:
ISWORD and REPETITION on all connections (except connections of regions on
themselves).
A RESULT:
Connection from LOTC to vIFG (Parameters):
1.DCM:
objetcs-1stPresentation(Modulatory Effect):Mean = 0,0126; Std.Dev. = 0,01829
objetcs-2ndPresentation(Modulatory Effect):Mean = 0,0057; Std.Dev. = 0,01755
words-1stPresentation(Modulatory Effect): Mean = -0,0029; Std.Dev. = 0,01204
words-2ndPresentation(Modulatory Effect): Mean = 0,0072; Std.Dev. = 0,00948
->Running Repeated Measures ANOVA on theses params (1. Factor: ISWORD, 2.
Factor: REPETITION) gives no effect of ISWORD. But: Means reveal a tendency
towards an interaction ISWORDxREPETITION
2.DCM
ISWORD(Modulatory Effect): Mean = 0,0068; Std.Dev. = 0,0046
->t-testing this against zero gives a significant modulatory effect of ISWORD.
So the results of the two models differ. Can you give me a hint????
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