[Eeglablist] del2map()
Tom Campbell
tom.campbell at helsinki.fi
Thu Dec 15 07:25:04 PST 2005
Dear eeglab experts,
I am trying to a scalp current density analysis with EEGLAB. One approach
to doing this is to "take the spatial derivative of spherical spline
functions" and the consequent value comes out in mA/m3. For instance, an
N1 of 10 uV would lead to corresponding scalp current density analysis
values of 2 milli-A/m3.
e.g. Alcaini, Giard, Thevenet, Pernier (1994) Psychophysiology 31, 611-615.
I see there is a function called del2map() that I think performs this
whole operation for the points at electrodes only and not the interpolated
points using the input of a .loc file, denoting the locations of the
electrodes, and vector of amplitudes. Is there a difference between a the
discrete laplacian and a surface laplacian?
When I input this vector of amplitudes in uV (e.g. 2.6) I get the
corresponding output of a much lower order (e.g.2.6 uV -> 0.0017). Please,
is this output expressed in Amps/m3 or something else?
I have then tried using the headplot() function that seems to produce
plausible distribution maps, that I take interpolates across the surface
of a model of the scalp. Taking the whole process together, please, is
this functionally-identical to "taking the spatial derivative of spherical
spline functions"?
--
best regards,
________________________________________________________________________
Tom Campbell e-mail:tom.campbell at helsinki.fi
Helsinki Collegium for Advanced Studies tel: +358-9 191 23256
University of Helsinki, Finland fax: +358-9 191 22924
P.O.Box 4 (Fabianinkatu 24) home: +358-4 154 09764
FIN-00014 University of Helsinki
Finland
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