[FieldTrip] ft_preprocessing high-pass filtering question

[Thomas Hartmann]

hi aaron,
filtering is generally applied after the data have been epoched. to avoid the filter artifacts you are speaking about, we normally define epochs that are sufficiently larger so that these artifacts would be in data we are not interested in. about 1s at both ends of the epoch should be enough in most cases. but you better check... later you can use ft_redefinetrial to discard that extra data.
hope this helps. 
best,
thomas



Aaron Schurger <aaron.schurger at gmail.com> schrieb:
>Hi,
>When you read in a data file using ft_preprocessing, with high-pass
>filtering, is the high-pass filter applied before the data are epoched
>(i.e. on the entire time series for the whole data file), or is the
>high-pass filter applied separately to each epoch? For very low
>frequencies (with period longer than one data epoch) this will make a
>difference.
>Thanks!
>Aaron
>
>--
>Aaron Schurger, PhD
>Post-doctoral researcher
>INSERM U992 / NeuroSpin
>CEA - Saclay, France
>+33-1-69-08-66-47
>aaron.schurger at gmail.com
>http://www.unicog.org
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Dr. Thomas Hartmann

CIMeC - Center for Mind/Brain Sciences
Università degli Studi di Trento
via delle Regole, 101
38060 Mattarello (TN)
ITALY

Tel: +39 0461 28 2779
Fax: +39 0461 28 3066
Email: thomas.hartmann at th-ht.de
Homepage: http://sites.google.com/site/obobcimec/

"I am a brain, Watson. The rest of me is a mere appendix. " (Arthur Conan Doyle)
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