[FieldTrip] Difference ERP source localisation methodology

[Milan Mitka]

Dear FieldTrip users,

I'm a master's student at the Comenius University in Bratislava, Slovakia, currently looking into source reconstruction of event-related potentials.

I have a quick methodological question regarding the localisation of event-related potentials which are obtained as difference waves – in my case the rotation-related negativity – by subtracting the standard condition (upright stimuli) from experimental conditions (stimuli rotated to a given degree).

Should I a) perform the source reconstruction on the averaged data for each condition and trial, or should I b) first subtract the standard condition from all experimental conditions for every trial and then reconstruct the sources?

Thank you.

Yours faithfully
Milan