[FieldTrip] CTF MEG issue

Pelt, S. van (Stan) stan.vanpelt at donders.ru.nl
Fri Oct 21 13:49:43 CEST 2016

Dear José,

I’ve forwarded your email to the FieldTrip email discussion list, since this is a more appropriate forum for a question like this (more experts=more potential answers).

10-50pT is way too strong to be a brain signal I’m afraid. Typical range would be 10-100 fT for CTF data, so your signal is more than 2 orders of magnitude higher.  I think it is most likely noise coming from outside the scanner (room).

Regarding the use of ft_databrowser, this is nicely decribed in the following tutorial: http://www.fieldtriptoolbox.org/tutorial/visual_artifact_rejection#use_ft_databrowser_to_mark_the_artifacts_manually

Scaling will be done automatically if you only plot the MEG-channels. So you do not need to specify cfg.megscale (or cfg.eogscale, for that matter).


From: joseluisblues at gmail.com [mailto:joseluisblues at gmail.com] On Behalf Of José Luis
Sent: vrijdag 21 oktober 2016 12:30
To: Pelt, S. van (Stan)
Subject: CTF MEG issue

Dear Stan Van Pelt,

I found your post in the Fieldtrip list and I thought you could help with an issue I have with my CTF MEG data,

I have analysed this data for an ERF study with a home-made software a few years ago. Now I am re-analysing this data to investigate oscillatory activity,

I usually never pay attention to the range of my raw data since I will always end up with averages values of ERFs around the typical 10-30 fT range. However, looking now to my raw data I find it on the range of 10000 - 50000 fT. My guess is that this should be Ok, since ERFs are always smaller in size relative to the raw data. I would like to check this with someone that has CTF MEG data.

Second, since is not in the typical range I have the issue of visualizing my data with ft_databrowser. So the typical setting with:

cfg.alim = 1e-12;
cfg.megscale = 1;
cfg.eogscale = 5e-8;
doesn't work for me,

I would like to know how do you manage to visualize your data,

Many thanks in advance,

By the way, the link to your paper "Higher-level processes in the formation and application of associations during action understanding" is not working properly,


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