[Eeglablist] EOG

[Dien, Joseph]

What was the problem with the data events?  No one told me they ran into a
problem with my code.  I'm no longer working with ERPSS data but might be
willing to fix it if it wasn't too much trouble.

Cheers!

Joe


-----Original Message-----
From:	Arnaud Delorme [mailto:arno at salk.edu]
Sent:	Fri 8/29/2003 6:47 PM
To:	Timothy O'Keefe
Cc:	eeglablist at sccn.ucsd.edu
Subject:	Re: [Eeglablist] EOG

Timothy O'Keefe wrote:


That seems odd to me because we are able to import bipolar VEO and HEO

into EEGLAB (we use Digitize acquisition software whcih records into

erpss format). They both come up as channels 63 and 64 (as they are

recorded) AND we have imported and exported (without running ICA) and

the output yeilds identical datasets. I don't know if that could be a

result of how MANSCAN codes bipolar electrodes? Though Arno did say that

"EEGLAB can not yet handle properly bipolar channels". That is confusing

to me because we have had no problems as of yet removing blinks. 

The current problem is that EEGLAB does not store a reference for each
channel. As a result, it can not make the difference between eye channels
recorded in a bipolar montage and eye channels recorded using the same
reference as the EEG scalp electrodes. To solve this problem, in the future,
we intend to include a reference for each channel in the channel structure.
This is why EEGLAB cannot handle eye channels properly.

What would happen if you run ICA on all channels (including bipolar
channels)?
We expect that ICA might dedicate (in theory) some components to account for
the different references. In theory, we think that ICA component should be
able to resolve the multiple reference problem and find some kind of common
reference.
However no study has been done on this yet. 

Does

readses.m fix this (Arno, you should know about readses.m)?  I'm not so

sure cuz Iv'e used the read_erpss function and that reads them in fine

too. 

Neither readses() nor read_erpss() fix this problem (readses() is not an
eeglab function; it was kindly sent to us to import compressed ERPSS data
but, since it could not handle data events properly, we chose to augment our
read_erpss() function to import compressed ERPSS data).



Also, we reference everything to the nose inc. HEO and VEO.

We think that this is the best option if you are planning to include these
channels in the ICA decomposition.

Arno

-- 

Arnaud Delorme, Ph.D. 
Computational Neurobiology Lab, Salk Institute 
10010 North Torrey Pines Road 
La Jolla, CA 92037 USA 

Tel : (+1)-858-458-1927 ext 15 
Fax : (+1)-858-458-1847 
Web page : www.sccn.ucsd.edu/~arno <http://www.sccn.ucsd.edu/%7Earno>