Dear SPMers,
I've got some questions about parametric modulations.
We conducted a study in which participants heard two types of
sentences (lets name them c1 and c2) and had to categorized them.
When we built these sentences (during a pretest), we obtained a
characteristic (such as degree of familiarity) and we would like to
see the effect of this characteristic on activations.
My first idea was to set it as a parametric modulation supposing a
linear increase of activations as this characteristic increase (1st
order, right ?).
However, I wonder if this parametric modulation is considered as a
regressor of non-interest in the design ?
Does it mean that if I set the contrast c1 vs c2 from the
design I set the PM, it will mean that the resulting activations
will be without the effect of PM ?
Regards,
Alexandre