[Eeglablist] Is dipfit ever used for purposes other than localising source space data?
arno at ucsd.edu
Fri Jul 12 21:11:08 PDT 2019
> Let me tell you dirty secret of dipfit.
> In order for cortical activation to be recorded at the scalp level without
> averaging, the patch size should be > 1 inch^2 (Nunez and Srinivasan,
> 2006). However, dipole model assumes a spatial point with 6 parameters.
> Therefore, estimating dipolar sources of scalp-recorded potential means to
> model spatially spread cortical patch with a point. This is a fundamental
> violation of the dipole model.
The dipole model is a mathematical tool that works well to summarize/compress data (6 values; 3 position; 2 moment; 1 amplitude) can often explain scalp topographies with 256 channels with 99% accuracy which indicates that this is a “good” model (6 numbers explaining 256 numbers). We have never claimed that ICA components localize to point like regions (the flux of current in a small patch of cortex can be well represented with a point like dipole at a slightly deeper location - I believe it is mathematically equivalent but would welcome validation from a source localization expert).
If you do not like dipoles, in Dipfit 3 you can also use eLoreta to calculate distributed source models associated with ICA components.
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