even one more dipole question...symmetry constraint...

Markus Bauer m.bauer at FIL.ION.UCL.AC.UK
Wed May 28 16:45:16 CEST 2008

....what precisely is the consequence of the symmetry constraint on the
calculated leadfields for symmetrical sources ?

I used the symmetry constraint for fitting two dipoles (for bilat. S2)
and looked at the respective leadfields of the corresponding
"individual" dipoles - to find out that they rather look not so
individual at all...
the coefficients of both had bilateral maxima, as the leadfields being a
mixture of the two individual dipoles, being symmetric along some axes
(y and z ?) and antisymmetric along the others (x?)

I do not quite understand this, cause I assumed the symmetry constraint
was only used to find the location parameter but the leadfields would
then be calculated for each position independently....
but this does not seem to be the case. are there any assumptions about
correlations of symmetric sources (dipoles) going in here to suppress
the respective other source ?
is there a reference to that ?


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