[FieldTrip] EEGLAB integration code question

[Jan Brøgger]

I just submitted a pull request to read Nicolet/Nervus files with fieldtrip
(https://github.com/fieldtrip/fieldtrip/pull/186) based on Joost Wagenaar’s
code from https://github.com/ieeg-portal/Nicolet-Reader with some updates
from me. Nicolet/Nervus is popular for clinical EEG. The chief advantage is
that it reads the file without depending on any external (vendor-supplied)
DLLs or conversion to EDF.

 

I have two questions that concern EEGLAB and fieldtrip integration:

1.       How can I make EEGLAB know that the Nervus/Nicolet EEG file read
with fieldtrip was originally recorded with a common reference (Fp1-REF,
Fp2-REF)? As far as I know, almost all clinical EEG is recorded with REF in
this way. There is an example in ft_read_header.m line 299 for the ‘Anywave’
format, which says “hdr.reference = orig.reference(:);” but apparently
EEGLAB doesn’t use this field.   In fieldtrip2eeglab.m there is no
functionality to say that this is a common reference.  There are many
references in the EEGLAB code similar to EEG.ref = ‘common’ but I can’t
quite make heads or tails of it.

2.       How can I make EEGLAB know the original filename of the
Nervus/Nicolet EEG file read with fieldtrip? In fieldtrip2eeglab.m line 25
it simply says “EEG.filename   = '';”. Could I submit a pull request to
EEGLAB with “EEG.filename = hdr.filename;” (with a check to see if the
filename field exists?)

3.       There are often breaks in clinical EEG recordings (e.g. adjusting
the photic lamps, instructing in hyperventilation etc.). Currently the
Nicolet/Nervus code handles this by creating events of type ‘boundary’,
which should make it work for EEGLAB. I hope I don’t have to use the
“trials” functionality of fieldtrip to indicate discontinuities. Will
fieldtrip understand events of type ‘boundary’?

 

 

Yours sincerely,

 

Jan Brogger

Clinical neurophysiologist/software developer, MD PhD

Bergen, Norway

 

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