[Eeglablist] One or two dipoles

[Makoto Miyakoshi]

Dear Pål,

Thank you for asking a very important question.

> just reflect uncorrelated activity has to be decided from the signal and
the situation.

As long as ICA works, this never happens. This is because if ICA finds two
foci, it means that they oscillate together in synch.

>By the way, it seems like the two dipoles are placed symmetrically. Why?

By default symmetry constraint is on (checked). You can uncheck it to see
what happens. The theoretical reason for this is that synchronization of
visual and motor cortices is mediated by corpus callosum and known to have
symmetrical sources (see fMRI studies...) Interestingly, the auditory
cortex seems to be somewhat different; ICA never gave me a paired auditory
sources.

Makoto


2013/2/7 Pål Gunnar Larsson <pall at ous-hf.no>

>   It is one major source here - left parietal. Then there is a weak right
> parietal field. If it is a source of interest or just reflect uncorrelated
> activity has to be decided from the signal and the situation. ****
>
> ** **
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> By the way, it seems like the two dipoles are placed symmetrically. Why?**
> **
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> Pål****
>
> ** **
>
> ** **
>
> Pål G. Larsson M.D., Dr. philos.****
>
> Head of Clinical Neurophysiology
> Department of Neurosurgery ****
>
> Division of Surgery and Clinical Neuroscience****
>
>
> Oslo University Hospital
> Po.box 4950 Nydalen****
>
> 0424 Oslo ****
>
> Norway ****
>
> Tel:  (+47) 23074407
> Mobile: (+47) 93429791
> E-mail: pal.gunnar.larsson at ous-hf.no ****
>
> non-sensitive****
>
>  ****
>
> ** **
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> ** **
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> Dear Bernhardsson,****
>
> ** **
>
> Definitely two dipoles. It's not primarily because much smaller r.v., but
> rather because your scalp topo shows bilateral foci.****
>
> ** **
>
> Makoto****
>
> 2013/2/7 Bernhardsson Jens <Jens.Bernhardsson at miun.se>****
>
> Hello,****
>
>  ****
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>  ****
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> How would you dipole fit this component? ****
>
>  ****
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> I do not find it sufficient to fit this component with only one dipole.
> However, the symmetrical dipole fitting is not as clear cut as it is with
> the m-shaped bilateral occipital component. The corresponding right sided
> topographical map (not attached) do not have this bilateral activation, and
> fits fine with one dipole (rv 1.7%). ****
>
>  ****
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> So, one or two dipoles?****
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>  ****
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>  ****
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> ****
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>  ****
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>  ****
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> Best****
>
> Jens****
>
>  ****
>
>
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> --
> Makoto Miyakoshi
> JSPS Postdoctral Fellow for Research Abroad
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego****
>



-- 
Makoto Miyakoshi
JSPS Postdoctral Fellow for Research Abroad
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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