[Eeglablist] Is dipfit ever used for purposes other than localising source space data?

[Makoto Miyakoshi]

Dear Kaelasha,

> will dipfit ever be useful if you are content carrying out the analysis
at the level of the electrodes or sensors (not in reconstructed anatomical
space)?*

This question is strange. If I rephrase it, 'Is dipfit useful when you
don't need dipfit' So the answer should be naturally 'no'.

Dear Ryan,

> If you don't plan to use ICA at all then I can't think of any purpose of
using dipfit.

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.

Recently, I got convinced that the reason why we often find physiologically
invalid deep dipoles should be because ICA returns fairly wide-spread
cortical area as an independent source. SCCN has been publishing papers
claiming that ICA finds very small cortical patches, but I found this claim
to be against the widely accepted model. I want to work on this issue to
make our dogma more plausible.

Makoto

On Mon, Jul 8, 2019 at 4:51 AM Kaelasha Tyler <kaelasha.tyler at gmail.com>
wrote:

> Hi all,
>
> EEG and MEG data can be analysed at the level of electrodes/sensors, or on
> the data as it is reconstructed back into anatomical space in the brain,
> using are range of processes (Beamforming, dipole fitting, LORETA etc).
>
> *My question is: will dipfit ever be useful if you are content carrying out
> the analysis at the level of the electrodes or sensors (not in
> reconstructed anatomical space)?*
>
> To explain:
> I am replicating an analysis in the literature, and reference in the paper
> I am following is made to fitting dipoles using dipfit2.2. However I am not
> needing to calculate eeg as it wold have occurred within the brain, but am
> content performing the analysis on ICA components of data recorded at the
> electrodes.
>
> In this case, is there any need at all to fit dipoles using dipfit2.2 ?
> Does using diptfit serve any other purpose?
>
> Thanks in advance.
> Kaelasha
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-- 
Makoto Miyakoshi
Assistant Project Scientist, Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego