Hi,
We have an event-related study containing 2 groups (Hydro and
placebo). The Hydro group has been injected with hydrocortisol. Each
subject had one session with a total of 90 scans. There are 3 types of
stimuli, but for this analysis we want to analyse only the first type.
TR = 3.25 and ISI is 16 seconds. The order of the stimuli is identical
for each subject. We are using SPM96b with the ER-toolkit.
QUESTIONS
We wish to compare Hydro - placebo to see if there are extra activations
in the Hydro group (in the contrasts, the Hydro will have 1 and placebo
will have -1).
Here is the procedure (see below). Does this procedure sounds right?
Also, for each type of stimuli, there were 3 consecutive scans taken.
Once we set the stimuli onset, how does it know to take 3 scans per
stimuli?
# of session or subjects: 13
Are these replications?: No
Loop
select scans for session 1
select scans for session 2
ect. (up to 13)
Threshold for F, p =: .05
Interscan Interval (secs): 3.25
Epoch or event-related fMRI: Event
Select basis set: hrf (alone)
---------------------------------------------------------
Loop
Number of event types: 1
Loop
Inter-stimulus intervals: Variable
Stimulus onset items (scans): 10 13 31 43 67 70 76 79 85 88
... for each subject
make inferences about: Pairewise comparisons
------------------------------------------------------------
# of confounds: 0
High pass filter: Yes
Cut-Off period (secs): 26
Remove global effects: Ancova
Remove effects on response: Yes
Time x response interaction: No
# contrast: 2
[13] contrast 1: 1 1 1 -1 -1 1 -1 -1 -1 -1 -1 1 1 (Hydro-Placebo)
[13] contrast 2: -1 -1 -1 1 1 -1 1 1 1 1 1 -1 -1 (Placebo-Hydro)
Temporal smoothing fwhm-secs: 4
These are simple questions but I am still in the learning curve.
Thanks.
Claude Breault Ph.D
Institut universitaire de gériatrie de Montréal
4565 Queen Mary, Montreal
Québec, Canada H3W 1W5
(514) 340-3540 ext. 4001
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