[FieldTrip] importing CeeGraph EEG data in Fieldtrip & iEEG analysis

[Michiel van Elk]

Dear Fieldtrippers,

Recently I acquired iEEG data with a BioLogic CeeGraph system which
generates a single file with an '.eeg' extension. It took me quite
some time to figure out how to read in the data in a format that is
usable in Fieldtrip, so here is the trick for anyone who ever runs
into the same problem (should work for EEGlab as well).

The latest version of Cartool software is the only software I found
that is capable of reading in the CeeGraph data
(http://cartoolcommunity.unige.ch/). Next, the individual tracks can
be exported in an 'eph'-format. This takes quite some time and
generates 3 separate files:

- an '.eph' file: which is a tab-separated text file with the
dimensions [nr_samples x nr_ electrodes]
- a '.mrk' file: containing the markers and the corresponding samples
- a '.vrb' file: giving a summary of the conversion process.

The first two files can be relatively easily imported in Matlab using
custom-made scripts (textread function) and transformed in a format
that Fieldtrip likes:)

In addition I was wondering if anyone has recommendations for the
preprocessing of iEEG data for subsequent LFP and TFR analysis (e.g.
re-reference data or not, which filter settings, where to put the
baseline)? In the literature I could not find a 'gold standard' and
people from different groups are doing different things.

Any help would be greatly appreciated!

Thanks,
Michiel van Elk

-- 
mail: michielvanelk at gmail.com
phone: (+41) 76-2271095
web: www.michielvanelk.com