[Eeglablist] Channel locations

[Sergei Shishkin]

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
>---------------------------------------------------------------
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