[FieldTrip] adding info about individual trials

Stephen Politzer-Ahles politzerahless at gmail.com
Sun Aug 20 14:01:45 CEST 2017

This really depends what you want to use that information for. Normally I
would think that all trials should be preprocessed in the same way
regardless of condition, so I don't really need this information at that
stage, but later on it might be useful for things like regressing ERP
amplitude on word length or something. But for stuff like this you don't
necessarily have to have this information *in* the data structure.

For example, imagine I want to know which word was presented each trial.
Typically, I have that list in a text file somewhere, in order (i.e., the
first line of the text file is trial 1, the second line is trial 2, etc.).
Then I do my various preprocessing of the EEG data in fieldtrip. Rather
than actually removing the trials with artifacts, at first I just keep a
list of which trials have artifact (or, better yet, which trials are
'good', without artifacts). Then I can use that list at the end of my
processing pipeline to pull out the good trials and match them up to which
words they are, and I can run whatever statistics I need on that. But there
is no fieldtrip-specific tricks about that; I just have a text file listing
all the information I need and I read that into MATLAB.

Stephen Politzer-Ahles
The Hong Kong Polytechnic University
Department of Chinese and Bilingual Studies

> ------------------------------
> Message: 2
> Date: Sat, 19 Aug 2017 18:42:57 +0200
> From: Roberto Petrosino <robpetrosino at gmail.com>
> To: fieldtrip at science.ru.nl
> Subject: [FieldTrip] adding info about individual trials
> Message-ID: <8E89FC7C-FA23-42AE-B0D9-3981F5B8241E at gmail.com>
> Content-Type: text/plain; charset="utf-8"
> Hello everyone,
> I just started learning FieldTrip, and I am still adjusting to it, so
> apologies if my question is very basic.
> Before running standard pre-processing steps and artifact rejection, I
> need to add specific information about individual trials of my non-epoched
> EEG data (i.e., which word was presented for specific trials), but I can?t
> find my way in the documentation online. Is there any specific function it
> might be appropriate for this purpose?
> Thanks in advance,
> -Roberto
> ----------
> Roberto Petrosino
> Ph.D. Student in Linguistics
> CT Institute for the Brain and Cognitive Sciences
> University of Connecticut
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