[Eeglablist] Channel locations

[Arnaud Delorme]

  It is true that due to smoothing in scalp plots, if the EOG are 
visible on the 2-D scalp map, there can be an impression  of some 
activity at nearest frontal electrodes when it is registered only with 
EOG electrodes. However, all electrodes that are considered outside the 
2-D head (depending on the shrink factor used in pop_chanedit) are not 
used for 2-D interpolation.

Right now, every channel must have a location. For EKG channels for 
instance, you must specify coordinates outside of the head (radius = 1 
for instance). In future versions however, each channel will have a type 
( 'EEG','REF','ECG', 'TTL' 'EOG' 'MEG' ), a reference field, and an 
optional gain, range and calibration field.

Best

Arno

> Sergei Shishkin wrote:
>
>> Hi,
>>
>> 1) The ICA itself in EEGLAB can be done without any channel location 
>> file.
>>
>> 2) However, in the current version such file is really necessary for 
>> viewing, e.g., scalp
>> projections (maps) for ICs. And, indeed, it is often useful to have a 
>> plot for electrodes
>> placed outside the scalp. Moreover, even adding EOG electrodes to 
>> maps (as is suggested
>> by the authors) is often misleading, because at the scalp maps they 
>> cannot be placed at
>> their real locations and because different type of reference can be 
>> used (e.g., bipolar
>> instead of monopolar). Due to smoothing, there can be an impression 
>> of some activity at
>> nearest frontal electrodes when it is registered only with EOG 
>> electrodes.
>>
>> Probably the best solution for visualizing non-scalp channels in the 
>> future versions could be
>> to place some additional subplot(s) for non-scalp electrodes outside 
>> the scalp map.
>>
>> Best Regards,
>> Sergei
>>
>> Sergei L. Shishkin, PhD
>> Laboratory for Advanced Brain Signal Processing
>> Brain Science Institute, RIKEN
>> 2-1 Hirosawa, Wako-shi, Saitama
>> 351-0198 JAPAN
>> http://www.bsp.brain.riken.go.jp/
>>
>>
>>
>> Gaurav Srivastava wrote:
>>
>>> Hi,
>>> I am curious as to why exactly do we need the channel location file 
>>> while
>>> performing ICA analysis in EEGLAB. Are the electrode separations 
>>> used in
>>> some way to determine the mixing matrix? Because intuitively it 
>>> makes sense
>>> that any electrode far away from an independent neurological source 
>>> will
>>> have less contribution from it than an electrode nearer to it.
>>>
>>> Also if we are making simultaneous EKG measurements and want to include
>>> these channels in ICA analysis, what will be their electrode 
>>> locations ?
>>>
>>> Best Regards,
>>> Gaurav.
>>>
>>> *** Keep the faith. It's too precious to lose. ***
>>> ---------------------------------------------------------------
>>> Gaurav Srivastava,
>>> Graduate Student, EE
>>> Stanford University, CA 94305
>>> ---------------------------------------------------------------
>>>
>>> _______________________________________________
>>> Eeglablist mailing list
>>> Eeglablist at sccn.ucsd.edu
>>> eeglablist page: http://www.sccn.ucsd.edu/eeglab/eeglabmail.html
>>> To unsubscribe, send an empty email to eeglablist-unsub at sccn.ucsd.edu
>>>
>>>
>>>  
>>>
>>
>>
>> _______________________________________________
>> Eeglablist mailing list
>> Eeglablist at sccn.ucsd.edu
>> eeglablist page: http://www.sccn.ucsd.edu/eeglab/eeglabmail.html
>> To unsubscribe, send an empty email to eeglablist-unsub at sccn.ucsd.edu
>>
>>
>
>
> -- 
>
> *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>
>
>


-- 

*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>


-- 

* Arnaud Delorme <http://www.sccn.ucsd.edu/%7Earno>, Ph.D.* , SCCN, 
UCSD, San Diego, USA

*SCCN main page:* www.sccn.ucsd.edu <http://www.sccn.ucsd.edu/>
*EEGLAB main page:* www.sccn.ucsd.edu/eeglab/ 
<http://www.sccn.ucsd.edu/eeglab>
*EEGLAB documentation:* www.sccn.ucsd.edu/eeglab/eeglabdocs.html 
<http://www.sccn.ucsd.edu/eeglab/eeglabdocs.html>
*EEGLAB FAQ page:* www.sccn.ucsd.edu/eeglab/eeglabfaq.html 
<http://www.sccn.ucsd.edu/eeglab/eeglabfaq.html>
*EEGLAB mailing lists:* www.sccn.ucsd.edu/eeglab/eeglabmail.html 
<http://www.sccn.ucsd.edu/eeglab/eeglabmail.html>


-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20030507/e8a1be1e/attachment.htm