[Eeglablist] Why most of good 'brain' ICs are 'dipolar' with show 'red'-centered scalp topos, although 2/3 of the cortex is in sulci?

[Евгений Машеров]

Thanks.

> Hello Evgenii and Scott,
> 
> I worked on non-invasive head tissue estimation using scalp current injection with Don at EGI while I was employed there 1994-2004. If you give me a few days I can point you to some literature.
> 
> -Jeff Eriksen
> 
> -----Original Message-----
> From: eeglablist <eeglablist-bounces at sccn.ucsd.edu> On Behalf Of Scott Makeig via eeglablist
> Sent: Wednesday, January 10, 2024 8:46 AM
> To: Евгений Машеров <emasherov at yandex.ru>
> Cc: eeglablist at sccn.ucsd.edu
> Subject: Re: [Eeglablist] Why most of good 'brain' ICs are 'dipolar' with show 'red'-centerd scalp topos, although 2/3 of the cortex is in sulci?
> 
> There was an abstract presentation at a company-sponsored? session at OHBM several years ago. I am sure Don is still interested <dmtucker at mac.com>
> 
> Scott
> 
> On Tue, Jan 9, 2024 at 12:33 AM Евгений Машеров <emasherov at yandex.ru> wrote:
> 
>> Thank you. I would like to clarify his methodology. Perhaps it is
>> described in detail somewhere? It seems to me that the frequency at
>> which the impedance is measured may be significant here.
>>
>> Eugen Masherov
>>
>>> Yes, this electrical stimulation approach was attempted by Don
>>> Tucker's
>> EGI
>>> group for many years - with results that were not encouraging, the
>> problem
>>> being that almost all the injected current flows through the scalp,
>>> whose local and time-varying conductivity also then has significant effect...
>> The
>>> SCALE approach treats the independent component signals compatible
>>> with
>> an
>>> effective source in cortex (having a strongly dipolar scalp
>>> projection
>> with
>>> equivalent dipole located in brain) as cortical stimulations, and
>>> iteratively finds the (single) skull conductivity value that
>>> minimizes reconstruction error of the brain sources to 'sparse,
>>> compact, and smoothly' varying distribution (sometime, two
>>> bilaterally near-symmetric distributions) on the imaged cortical
>>> surface - using an electrical forward problem head model constructed
>>> from an individual MR image - the SCS source inversion algorithm of
>>> Cao Cheng. Our next step should be to build a multidimensional skull
>>> conductivity map. Again, we
>> are
>>> attempting to put the SCALE software on NSG (
>> https://urldefense.com/v3/__http://www.nsgportal.org__;!!Mih3wA!BNS_5a
>> ZCEDYflkuo2qfpDZgsY0Z-xv87AU3QM1QiNdQklstxqDvGifU6oaUANNcbLSF18LJVuTtk
>> Yo2KIrZI$
>> ) for free
>>> use.
>>>
>>> Scott Makeig
>>>
> 
> --
> Scott Makeig, Research Scientist and Director, Swartz Center for Computational Neuroscience, Institute for Neural Computation, University of California San Diego, La Jolla CA 92093-0559, http://sccn.ucsd.edu/~scott _______________________________________________
> Eeglablist page: http://sccn.ucsd.edu/eeglab/eeglabmail.html
> To unsubscribe, send an empty email to eeglablist-unsubscribe at sccn.ucsd.edu
> For digest mode, send an email with the subject "set digest mime" to eeglablist-request at sccn.ucsd.edu
> ________________________________
> IMPORTANT NOTICE: This communication, including any attachment, contains important information that may be confidential or privileged, and is intended solely for the entity or individual to whom it is addressed. If you are not the intended recipient, you should contact the sender and delete this message. Any unauthorized disclosure, copying, or distribution of this message is strictly prohibited. Nothing in this email, including any attachment, is intended to be a legally binding signature.