[FieldTrip] DICS conditions comparison

[Dimitri BAYLE]

Dear Fieldtrip-users,

I have a general question about source analysis comparison.
I want to compare visual alpha deactivation between 2 conditions (A and 
B), both containing a baseline (pre) interval and a poststimulus 
interval, and both showing a strong occipital visual deactivation when 
comparing the relative contrast ((preA-postA)/preA).

To compare A and B, should i calculated a common filter for the baseline 
and another one for the poststimulus interval, or used the same filter 
(calculated on which interval)?

After applying the filter to all individuals trials (pre and post 
stimulus), is it better to   1) average alls trials, then calculated the 
relative contrast for A and for B ((pre-post)/pre)), and                 
                                                                         
                                         substract A and B relative 
contrast to reveal the difference
or 2) calculated the relative contrast for each individuals trials, then 
average all relatives contrast per conditions (A and B), and substract A 
and B?

Thanks for your help

Dimitri