[Eeglablist] One or two dipoles

[Makoto Miyakoshi]

Dear Pal,

I agree with you that (slight) asymmetrical dipole fitting is more
realistic. It would be nice to have such 'almost symmetrical'
constraint rather than that of complete symmetry.

> you should take advantage of its superiority - the time
> resolution. I think you should follow your asymmetrical findings.

Just a note- EEGLAB primarily assumes that dipoles are fit to scalp
topos obtained from ICA. These IC scalp topos are time-invariant.

> I have been doing dipoling since the early 1990s (mainly in epilepsy).
> Symmetrical dipoles are rare, but they excists.

I respect your experience in the field and appreciate you share it
with us. Thank you.

Makoto



2013/2/10 Pål Gunnar Larsson <pall at ous-hf.no>:
> Dear Makoto
>
>
>
>
>
> 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.
>
>
>
> The propagation time through CC is about 10-15ms. This is way outside the
> time resolution in fMRI. However, fMRI has a superior space resolution, so
> using EEG, you should take advantage of its superiority - the time
> resolution. I think you should follow your asymmetrical findings.
>
>
>
> I have been doing dipoling since the early 1990s (mainly in epilepsy).
> Symmetrical dipoles are rare, but they excists.
>
>
>
>
>
> Pål
>
>
>
> 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.
>
>
>
> By the way, it seems like the two dipoles are placed symmetrically. Why?
>
>
>
>
>
> 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
>
>
>
>
>
>
>
>
>
> 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,
>
>
>
>
>
> How would you dipole fit this component?
>
>
>
> 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%).
>
>
>
> So, one or two dipoles?
>
>
>
>
>
>
>
>
>
> 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



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