[FieldTrip] Trial-dependant baseline correction

Marco Dahmane marco.dahmane at gmail.com
Thu Mar 22 13:13:18 CET 2012

Dear fellow Fieldtrippers,

I was having a small problem regarding baseline correction in FT.

My situation is rather simple : I have two types of trials, trials A and
trials B. Triggers A are always preceding triggers B, but the delay between
the two is NOT fixed.

I use triggers B to define my trials (for instance -0.5s to +0.5s).
Very straightforward.

However, I would like to use triggers A to define my baseline window. Say I
would like to use the one second preceding each trigger A as the baseline
for the following trial.

Until now the way I was going about it was rather tedious :
a) ft_preprocessing data as one big, long trial (filtering)
b) ft_definetrial to define long trials as starting from trigger A (origin)
to following trigger B (end)
*c) ft_preprocessing to baseline correct*
d) ft_redefinetrial with variable cfg.offset to set origin back to trigger B
e) ft_redefinetrial to take only window [ -0.5s ; +0.5s]

But I'm wondering whether that's not an overkill (especially since the
delay between triggers A and B can be quite long and make the preprocessing
really slow on my old machine).

Any advice is appreciated,

Best regards,
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