[Eeglablist] Spherical Coordinates of T1/T2 electrodes

[Robert Oostenveld]

Hi Christos

On 26 Jun 2006, at 10:02, xristos-alex wrote:
> I've constructed a .ced file so that I can import channel locations to
> EEGLab. However, I'm not pretty sure about the spherical  
> coordinates of the
> true anterior temporal electrodes T1/T2 (they're located 1cm above  
> a point
> that is one-third the anterior distance on a line from the external  
> auditory
> canal to the lateral canthus of the eye).
> I'm looking forward to anybody's response.

The T1/T2 electrodes are not defined in the Jasper (1958) 10-20  
standard or the AES (American Electroencephalographic Society)  
extended 10-20 standard (published in 1991 and 1994 and probably at  
more occasions), but they are given in the Chatrian et al. 1985 Am J  
EEG Technol paper. That paper is the proposal that led to the  
extended 10-20 system. The T1 electrode is also shown in Chatrian et  
al 1988 (see pubmed references below). The names have become slightly  
different in the AES standard, but the locations are the same.

There is one vertical "column" of electrodes running from Cz-T7  
(T7=T3), and one "column" running from Fz-F7. In between those two  
columns are the FC electrodes, i.e. FCz-FT7 (FT7=FC7). The T1  
electrode seems to be located further down along the FC-line. That  
would mean that the location of T1 is approximately the same as the  
location of FT9.

The name and positon of electrode FT9 is defined in the AES standard  
(see below for the reference), and the position of that electrode is  
also included in the spherical/BESA and realistic/standard-BEM  
electrode files included with the DIPFIT plugin. The electrode system  
definitions are clarified and extended to >=128 electodes in our  
(Oostenveld & Praamstra) 2001 paper. That paper also describes the  
FT9 location. I can send you a pdf reprint upon request (I will not  
send it to the complete EEGLAB mailing list). On http:// 
oase.uci.ru.nl/~roberto/index.php you can also find more information  
and references.

best regards,
Robert

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Robert Oostenveld, PhD
F.C. Donders Centre for Cognitive Neuroimaging
Radboud University Nijmegen
phone: +31-24-3619695
http://www.ru.nl/fcdonders/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

references:

Chatrian GE, Lettich E, Nelson PL.
Modified nomenclature for the "10%" electrode system.
J Clin Neurophysiol. 1988 Apr;5(2):183-6.

[No authors listed]
American Electroencephalographic Society guidelines for standard  
electrode position nomenclature.
J Clin Neurophysiol. 1991 Apr;8(2):200-2.

Oostenveld R, Praamstra P.
The five percent electrode system for high-resolution EEG and ERP  
measurements.
Clin Neurophysiol. 2001 Apr;112(4):713-9.