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

[K Jeffrey Eriksen]

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 _______________________________________________
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