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Nov 4, 2015 10:11 AM | davide cosmacini
Group level clarification
Dear Dr. McLaren,
I run a gPPI group level analysis but I have some problems of interpretation.
I have an event-related design with 9 different events (1 factor with 9 level) .
In order to run a random effects analysis, I have to create at the first level a contrast for each of my 9 conditions
(my PPI-interaction terms) and put them in the group level. So, in the second level my regressors will be only the
PPI-interaction terms but not the seed signal (eigenvariate) and the psychological term.
Is it correct?
When I look at the contrast estimates and 90% C.I. [F-test --> eye(9) ] for a specific voxel, How should I interpret the plot?
1) Can I interpret a condition alone? What does the baseline means?
for example, condition_1 = 0; A > 0; A < 0
2) It seems clear to me that the y axis in this plot doesn't represent % BOLD signal but I can't figure out what is it?
Thank you for your patience,
Davide
I run a gPPI group level analysis but I have some problems of interpretation.
I have an event-related design with 9 different events (1 factor with 9 level) .
In order to run a random effects analysis, I have to create at the first level a contrast for each of my 9 conditions
(my PPI-interaction terms) and put them in the group level. So, in the second level my regressors will be only the
PPI-interaction terms but not the seed signal (eigenvariate) and the psychological term.
Is it correct?
When I look at the contrast estimates and 90% C.I. [F-test --> eye(9) ] for a specific voxel, How should I interpret the plot?
1) Can I interpret a condition alone? What does the baseline means?
for example, condition_1 = 0; A > 0; A < 0
2) It seems clear to me that the y axis in this plot doesn't represent % BOLD signal but I can't figure out what is it?
Thank you for your patience,
Davide
Nov 4, 2015 01:11 PM | Donald McLaren
RE: Group level clarification
See inline responses below.
Originally posted by davide cosmacini:
1) Can I interpret a condition alone? What does the baseline means?
for example, condition_1 = 0; A > 0; A < 0
2) It seems clear to me that the y axis in this plot doesn't represent % BOLD signal but I can't figure out what is it?
Originally posted by davide cosmacini:
Dear Dr. McLaren,
I run a gPPI group level analysis but I have some problems of interpretation.
I have an event-related design with 9 different events (1 factor with 9 level) .
In order to run a random effects analysis, I have to create at the first level a contrast for each of my 9 conditions
(my PPI-interaction terms) and put them in the group level. So, in the second level my regressors will be only the
PPI-interaction terms but not the seed signal (eigenvariate) and the psychological term.
Is it correct?
When I look at the contrast estimates and 90% C.I. [F-test --> eye(9) ] for a specific voxel, How should I interpret the plot?
I run a gPPI group level analysis but I have some problems of interpretation.
I have an event-related design with 9 different events (1 factor with 9 level) .
In order to run a random effects analysis, I have to create at the first level a contrast for each of my 9 conditions
(my PPI-interaction terms) and put them in the group level. So, in the second level my regressors will be only the
PPI-interaction terms but not the seed signal (eigenvariate) and the psychological term.
Is it correct?
When I look at the contrast estimates and 90% C.I. [F-test --> eye(9) ] for a specific voxel, How should I interpret the plot?
>>> The contrast estimates for eye(9)
aren't meaningful. The group model needs to include a subject
factor and should use the flexible factorial model. The contrast
that can be used for getting the contrast estimates would be:
[eye(9) ones(9,n)/n] where n is the number of
subjects.
1) Can I interpret a condition alone? What does the baseline means?
for example, condition_1 = 0; A > 0; A < 0
>>> This means that condition_1 is
greater than or less than, respectively, the baseline slope between
the seed and target region.
2) It seems clear to me that the y axis in this plot doesn't represent % BOLD signal but I can't figure out what is it?
>> It is the change in slope between the
condition(s) or condition versus baseline for an individual
condition.
Thank you for your patience,
Davide
Thank you for your patience,
Davide
>> Hope this helps.
Nov 9, 2015 12:11 PM | davide cosmacini
RE: Group level clarification
Yes, it helps. Thank you very much for the clarification.
best,
davide
best,
davide