have an event-related design. The 1st level included the canonical HRF
and its time and dispersion derivatives, because we want to look if
there are difference in response shape between 2 groups. At the 1st
level analysis, I defined a t-contrast for each basis function
(HRF, TD and DD). The 2nd level analysis employed an ANOVA 3 (basis
functions) x 2 (groups). I did an F test defined as:
1 -1 0 0 0 0
0 0 1 -1 0 0
0 0 0 0 1 -1
- group2: HRF; group1 - group2: time der. and group1 - group2:
dispersion der.). This tells me which voxels have different activity
between the 2 groups with respect to either amplitude, either time, or
dispersion. I plotted the results, but I found it difficult to
understand/explain, as it's an F test. Moreover, as I understood from
Friston's paper (Friston et al. 1998, Neuroimage, 7:30-40) this tells
me how well the model fits or have I misunderstood the things?
My question is how can I look for differences in response shapes
between 2 groups combining the 3 basis functions?
Any suggestion is more than welcome.