Print

Print
Dear FSL users,

I am running an fMRI analysis in which we show 7 kind of stimulus to 4 different populations:
1. High Neuroticism (High N) trait personality taking a drug
2. Low Neuroticism (Low N) trait personality taking a drug
3. High Neuroticism trait personality taking a placebo
4. Low neuroticism trait personality taking a placebo
and see how they respond to those 7 different stimuli.

For the first level analysis we wanted to see the main activation of each stimulus and some comparisons between them:
EV1 EV2 EV3 EV4 EV5 EV6 EV7
1      0     0      0     0      0      0      EV1 effect
0      1     0      0     0      0      0      EV2 effect
...
1      0     0      0     0      0     -1      EV1 vs EV7
-1     0     0      0     0      0      1      EV1 vs EV7 (opposite)
...

For the high-level analysis we would like to see if there are any differences in the stimulus activation depending on the group the participant belongs to:

* EVs: Please find attached the EVs matrix used for the high-level analysis, where each EV corresponds to a single group (i.e. EV1 is HighDrug, EV2 is LowDrug etc).


* Contrasts & F-Test:
                                         HD  LD    HP   LP
C1  4 Groups Mean               1    1      1     1
C2  Drug Mean                      1    1      0     0
C3  Placebo Mean                 0    0      1     1
C4  High N Mean                   1    0      1     0
C5  Low N Mean                    0    1      0     1
C6  High N Drug Mean           1     0      0    0
C7  Low N Drug Mean            0     1      0    1
C8  High N Plac. Mean          0     0      1    0
C9  Low N Plac. Mean           0     0      0    1
C10 Main effect drug             1      1    -1    -1
C11 Main effect drug             -1     -1    1     1    (opposite)
C12 Main effect of N              1     -1    1     -1
C13 Main effect of N             -1     1    -1     1    (opposite)
C14 Main effect of N in drug   1     -1    0      0
C15 Main effect of N in drug   -1     1    0      0    (opposite)
C16 Main effect of N in Plac   0      0    1      -1
C17 Main effect of N in Plac   0      0    -1     1    (opposite)
C18 Main effect of drug HN    1      0     -1     0
C19 Main effect of drug HN    -1     0     1      0    (opposite)
C20 Main effect of drug LN     0      1     0      -1
C21 Main effect of drug LN     0      -1    0      1    (opposite)

HD: High N + Drug
LD: Low N + Drug
HP: High N + Placebo
LP: Low N + Pacebo

Does this design make sense, or is it necessary to model the effects of neuroticism and drug group in separate FEATs? And is it possible to examine an interaction effect between drug group and neuroticism using this design? Any kind of help would be very appreciated.

Thank you in advance.

Maria Serra-Blasco
Department of Psychiatry
Warneford Hospital
Oxford
OX3 7JX