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

[Downey, Ryan J]

In the paper you are referencing, they are running ICA and then picking the single independent component that best represents the P3 ERP they are interested in so they can have better a signal-to-noise ratio than channel-data. After running ICA, they are using dipfit to automatically reduce the number of components they later have to sort through with some other algorithm (COMPASS). So basically they are using dipfit to assist them in selecting the best IC. 

If you don't intend to replicate the paper exactly (using ICA) then I don't see why you would need dipfit. 


Ryan J. Downey
Postdoctoral Associate
Human Neuromechanics Laboratory
Biomedical Engineering Dept.
University of Florida




-----Original Message-----
From: eeglablist <eeglablist-bounces at sccn.ucsd.edu> On Behalf Of Kaelasha Tyler
Sent: Sunday, July 14, 2019 11:37 PM
To: Eric Rawls <elrawls at email.uark.edu>
Cc: eeglablist <eeglablist at sccn.ucsd.edu>
Subject: Re: [Eeglablist] Is dipfit ever used for purposes other than localising source space data?

Hi Eric,

Here is a link to the paper whose analysis I am replicating:
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.ncbi.nlm.nih.gov_pubmed_25348645&d=DwICAg&c=sJ6xIWYx-zLMB3EPkvcnVg&r=Xqv3i1MFyNQV9dhuL1e9BtqA0SbF1UWmfPtBzxDT0xY&m=U0BWwI4yJbHJW7vP4jpNtibfY_pcaDWpO5-gVC9eI9A&s=lkuJ7iUe_tYs4GC_hZwvB1X87gUDKxGYCcP1s-2SCr4&e= 

The use of Dipfit2.2 in conjunction with ICA is on page 474:

" ...The remaining components were fitted with individual inverse dipole solutions using the DIPFIT 2.2 algorithm. Components with nondipolar equivalent dipole solutions usually represent nonbrain signals ........and were also removed."

This paper does not deal source localisation per se, and this use of Dipfit is only in conjunction with removal of ICA components.

I just wasn't familiar with use of Dipfit in cases where there is no intention to analyse source based data, and wondered how necessary it really is?

Thanks for the help.

Cheers,
Kaelasha






On Tue, Jul 9, 2019 at 4:07 AM Eric Rawls <elrawls at email.uark.edu> wrote:

> Hi Kaelasha,
> Could you link to the paper you are trying to replicate?
> As others have mentioned, I have a hard time thinking of a use of 
> dipole fitting if you are categorically not interested in source localization.
> One possibility that I saw at a recent conference (don't know if the 
> paper is out yet, it was a poster presented by Sid Segalowitz) is to 
> remove all ICs except those localized to certain anatomical regions, 
> then to analyze the scalp projection made of only (for example) PFC generators.
> However, without knowledge of the analysis you're trying to replicate 
> this is speculatory.
> You can also technically fit a dipole to the scalp map of EEG 
> activation at a specific time point but this is not advisable, because 
> many individual dipoles are active at each point in the time series.
> Cheers
> Eric Rawls, M.S.
> Graduate Research Assistant, Instructor Department of Psychological 
> Sciences University of Arkansas
>
> On Mon, Jul 8, 2019 at 5:51 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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