[Eeglablist] Dipfit

[Makoto Miyakoshi]

Dear Jacquie,

I assume your channel locations were not digitized but just using 10-5
labels (i.e. Fz, Cz, Pz...) and 'looked up' channel locations using EEGLAB
function. Do followings.
1. Open channel edit GUI and press the button in top right 'optimize head
center'. Before and after doing this, check 2-D channel distributions
(bottom-left botton in the same GUI)
2. Most likely your head model corregistration is incorrect. When you do
it, thoroughly check if your channels and the head model are aligned
correctly, and the error between their channel locations are minimized (you
may use 'warp montage' if you can use it, otherwise you should do it
manually; which is still not too bad because you can use the same
parameters for other subjects).

Makoto


2013/5/9 Jacqueline Scholl <jacqueline.scholl at psy.ox.ac.uk>

> Dear Tarik,
>
> thanks a lot for your reply. I indeed hadn't seen the other questions
> about one or two dipoles, this was very useful!
>
> I've checked again my electrode alignment and I'm using the standard 10-20
> system with 36 electrodes. So I don't think this explains why dipoles for
> components that contain part of the ERP i'm interested in are localized
> outside the head. Is there anything else I could check?
>
> All the best
> Jacquie
>
>
> On Thu, May 9, 2013 at 1:38 AM, Tarik S Bel-Bahar <tarikbelbahar at gmail.com
> > wrote:
>
>> Greetings Jacqueline,
>>
>>
>> If you haven't had a chance to yet, please consider the following
>> resources I found by doing a google search on "eeglab list fitting two
>> dipoles".
>> The first link below is to the online eeglab wiki, which talks about
>> co-registration and about 1 versus 2 dipole fitting.
>> If you're not properly co-registered, this might the problem.
>> As a general rule I believe that the norm is that an ICA scalp map
>> with a focused component such as an event-related negativity
>>  is likely to be a single-dipole solution whereas a bilateral
>> occipito-temporal N170 would be a double-dipole solution (one left,
>> one right).
>> Hope this helps a bit!
>>
>>
>> A08: DIPFIT - SCCN
>>
>> sccn.ucsd.edu/wiki/A08:_DIPFIT
>>
>> [Eeglablist] One or two dipoles
>>
>> sccn.ucsd.edu/pipermail/eeglablist/2013/006296.html
>>
>> [Eeglablist] How many dipoles to fit?
>>
>> sccn.ucsd.edu/pipermail/eeglablist/2011/004026.html
>>
>> [Eeglablist] dipfitting for egi: how to align channels
>>
>> sccn.ucsd.edu/pipermail/eeglablist/2011/004240.html
>>
>
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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