Hi all,
Regarding the issue of delay maps:
We are running an fMRI experiment but with O2 breathing as a paradigm - to
get BOLD contrast and not functional stimuli for neuronal activity. Therefore
we have much higher %BOLD and large delay differences between areas in the
brain.
1.We are not sure we are using correctly the feat gui. Once we define
the "Add temporal derivative" does it automatically add an EV to our design
matrix? So if we have only one EV in our paradigm, and we define one EV, it
means that now we have two with the "delay" as a second EV? or we need to
define 2 EV in the "Number of original EVs"? If that is the case, then what
should we define in this EV? and in the "Contrasts"?
2 . We are not sure that this gives us what we want. We run as described in
the Course:
fslmaths pe2 -mul 100 -div pe1 -mas ../cluster_mask_zstat1 delay1
but the maps seems incorrect. When looking at the time course we do not see
differences in the delay between areas that are shown in the delay map with
a long delay and with area that are shown in the delay map with short delay
(even when the difference is few sec). In addition, it seems that areas that
are shown in the delay map with high delay usually have higher %BOLD,
compared to areas with short delay. Could that affect the derivative of the EV
so it "looks" like it is a delay, and actually it only a function of %BOLD?
Thank in advance
Moran
|